Types of kiwi fruit

Kiwi

Kiwi, (Actinidia deliciosa), also called kiwifruit or Chinese gooseberry, woody vine and edible fruit of the family Actinidiaceae. The plant is native to mainland China and Taiwan and is also grown commercially in New Zealand and California. The fruit has a slightly acid taste and can be eaten raw or cooked. The juice is sometimes used as a meat tenderizer. Raw kiwis are high in vitamins C and K.

kiwiKiwi fruit.André Karwath

Kiwi vines are dioecious, meaning that male and female flowers are borne on separate individuals. Generally, one male plant can facilitate the pollination of three to eight female plants. The ellipsoidal kiwi fruit is a true berry and has furry brownish green skin. The firm translucent green flesh has numerous edible purple-black seeds embedded around a white centre. The deciduous leaves are borne alternately on long petioles (leaf stems), and young leaves are covered with reddish hairs.

A number of other species are also grown for their fruits. Golden kiwi (Actinidia chinensis) has fewer hairs and yellower, sweeter flesh than A. deliciosa and is grown commercially in some places. Other kiwis include two cold-hardy species (A. arguta and A. kolomikta), Chinese egg gooseberry (A. coriacea), red kiwi (A. melanandra), silver vine (A. polygama), and purple kiwi (A. purpurea).

kiwi fruitsCluster of ripe kiwis (Actinidia chinensis).© Sinisa Botas/.com

Kiwi Plant Types – Different Varieties Of Kiwi Fruit

There are approximately 50 types of kiwi fruit. The variety you choose to grow in your landscape will depend upon your zone and the space you have available. Some vines can grow up to 40 feet, which requires excessive trellising and space. There are four species that are cultivated for gardens: arctic, hardy, fuzzy, and hairless (Actinidia chinensis). Each have different characteristics, frost tolerance and flavor. Choose your kiwi plant types by your location but also by your flavor and size preferences.

Types of Kiwi Fruit

Kiwis were once thought to be tropical to sub-tropical vines but careful breeding has resulted in cultivars that thrive in temperatures down to -30 degrees Fahrenheit (-34 C.), such as the Arctic kiwi or Actinidia kolomikta. This is good news for kiwi lovers who want to produce their own fruit.

Different varieties of kiwi may have seeded or seedless, fuzzy or smooth, green, brown, purple or red skin and green or golden yellow fleshed fruits. The choices are dazzling. Here are some of the most popular within the species.

Hardy Kiwis

Hardy kiwis are one of the newer vines developed for cooler season growing. These kiwi vine varieties are perfect for regions with light frosts and short growing seasons, such as the Pacific Northwest. They are hairless, green and small but pack a lot of flavor and are tolerant of conditions that the fuzzy kiwi cannot withstand.

  • Ananasnaya is a good representative of the type, which has green to purplish-red skin and fragrant fruit.
  • Dumbarton Oaks and Geneva are also highly productive, and Geneva is an early producer.
  • Issai is self-fertile and will not require a male pollinator to produce fruit. Fruits are borne in tight, attractive clusters.

Fuzzy Kiwis

  • Hayward is the most common kiwi found in grocery stores. It is only hardy in areas with mild winters.
  • Meander is another common one of the fuzzy kiwi vine varieties to try.
  • Saanichton 12 is a cultivar that is hardier than Hayward but the center of the fruit is reportedly quite tough. Both of these require a male for pollination and several are available which would be suitable partners.
  • Blake is a self-fruiting vine with very small oval fruits. It is a vigorous plant but the fruits are not as flavorful as Hayward or Saanichton 12.

Actinidia chinensis is closely related to the fuzzy types of kiwi fruit but is hairless. Tropical, Arctic Beauty and Pavlovskaya are other examples of A. chinensis.

Arctic Kiwi Plant Types

Arctic Beauty is the most cold tolerant of the different varieties of kiwi. It has extremely hardy fruit and pink and white variegation on the leaves, making it an attractive addition to the landscape. Fruits are smaller and sparser than the other kiwi vine varieties but sweet and delicious.

Krupnopladnaya has the largest fruit and Pautske is the most vigorous of the Arctic kiwis. Each of these does need male pollinators to produce fruit.

Kiwi vines can produce fruit almost anywhere today as long as they get full sun, training, pruning, plenty of water and feeding. These extreme hardy specimens can bring a touch of the tropics to even zones with cold winters. Just remember to provide a thick layer of mulch around the root zone and these tough kiwis will sprout back in spring.

There are several classifications of the genus Actinidia. At present, the chief cultivated varieties belong to the genus Actinidia deliciosa. The most outspread cultivars are Hayward and Bruno.
In 1983, in the Botanical Institute of Guangxi (China) the genus Actinidia was classified by means of describing the different areas of the 53 species, 5 varieties and 15 forms included in this genus, distributed spontaneously, from Ecuador to 50º of latitude North and from Japan (to the East) to Tibet (to the West). From this classification, A. Chinensis is subdivided in 3 botanical varieties: chinensis (with a glabrous fruit), hispida and setosa, (with a hairy fruit); the cultivars would be assigned to A. Chinensis var. hispida.
In 1984, the author of the previous classification and another researcher from New Zealand verified that the var. hispida had been already described by A. Chevalier as var. deliciosa, and therefore they decide to forget about this last denomination and they suggest to change A. chinensis var. deliciosa to Actinidia deliciosa.
Apart from A. Deliciosa, the species Actinidia arguta and A. kolomikta also bear edible fruit of certain interest.
The varieties of Actinidia cultivated nowadays are native to New Zealand. They are classified in feminine varieties and masculine or pollinating varieties.
– Feminine varieties: Abott, Bruno, Hayward, Monty, Kramer, Greensil, Allison, Vicent, Tewi, Gracie, Jones and Elmwood.
– Masculine varieties: Matua, Tomuri and M-3. The recently introduced varieties are M51, M52, M54, M56, Chieftain and Autari.
The plantations in Spain belong to Actinidia deliciosa, whose cultivar Hayward is the most spread and considered to be the prototype of fruit known as “Kiwi’. Some curious cultivators are introducing some clones bred in other countries like: “Hayward K”, “Hayward 8” or “Top Star”.

Often seen as the epitome of tropical fruit, the kiwi plant is more versatile than you might think! In fact, any area with mild winters, and a long growing season can easily support this gorgeous fruiting plant. Read on to learn more about this luscious fruit, and how to grow it in your home garden.

Fruchthandel_Magazin /

Did you know that the kiwi plant has more in common with grape vines than peach trees? Its graceful, spreading vines drape over trellises and walls. Lush, red vines, abundant flowers, and vibrant leaves provide an eye-catching display.

Add delicious, nutrient-dense fruit to the mix and you’ve got an exciting new addition to the garden. But, can you really grow a kiwi in North America? Absolutely!

Two Kinds of Kiwi

There are two varieties of kiwi plant. The fuzzy, comparatively large kiwis we’re used to seeing in North America; and their smooth-skinned, hardy cousins.

Tropical Kiwis

Buecherwurm_65 /

You know the fuzzy, cute kiwis at your local grocery store? The ones that fill up the corners of fruit baskets? Those popular little fruits are only suitable for growing in especially warm climates. They’re especially popular in southern Californian gardens or in sunny New Zealand.

Fuzzy kiwis (Actinidia chinensis) can’t tolerate temperatures below 10 degrees F, and thrive in long, hot summers in zones 7–9. They’re native to southern Asia, and in the right climate they’re vigorous, fast-growing, vine plants that can reach up to twenty feet. Much like hops, kiwis need a strong, tall trellis to grow on.

Unlike a grocery store kiwi, the hardy variety is a small, smooth fruit. Intensely flavored and addictively sweet, hardy kiwis don’t need to be peeled. You can pop them into your mouth whole, right off the plant.

Hardy kiwis (Actinidia kolomikta) are native to northern China and can survive winter temperatures down to -25 degrees F. Some Russian varieties can even thrive in winters that reach -35 degrees. If you’re interested in trying Kiwis in the Northeast or Midwest, check out varieties like “Natasha” and “Tatyana”.

Growing Hardy Kiwi Plants

purplejuice /

In this article, I’ll be focusing specifically on hardy kiwis, though most of the advice is adaptable to tropical kiwis. Hardy Kiwis are ideal in zones 5-9, but some varieties are adapted to colder climates as well.

Getting Started

Make sure you have plenty of room, as kiwis need a lot of space. The kiwi plant is a dramatic, draping vine that spreads quite a bit as it grows.

Plant your kiwi along a fence or arbor to give it some structured climbing space. Training your kiwi to climb will also preserve much of the fruit from rot and ground pests.

Starting kiwi is easiest with a rooted cutting or a young plant. You can start hardy kiwi from seeds, but the process of obtaining and cleaning seeds is often daunting. Many seed catalogues sell rooted plants and young potted kiwi vines that can be easily transplanted.

Male and Female

You will need both a male and female kiwi plant. Hardy kiwis aren’t able to self-pollinate, so plant a male kiwi to make sure your female kiwi plants bear fruit. You’ll only need one male for every 8 female kiwi plants. Keeping to the 1:8 balance allows you to get maximum fruit every season, without them taking over your garden entirely.

Coral-Creation /

It’s important to get a male and female of the same variety. This is because plants need to flower at the same time in order to pollinate. Different kiwi varieties flower at slightly different times. This could be tragic if the male blooms too early or late to pollinate his female vines.

Space and Sun

Kiwis need at least 10-18 feet between them to thrive. Remember, these are spreading vines—they need their space.

They also need well-drained soil and consistent, full sun in order to fruit properly. Kiwis love sunlight. They bask in it! Hardy kiwis especially seem to soak up sunlight while they have it, in order to survive the cold winters.

If you live in a desert climate, however, give your kiwis a bit of a sun break. In very hot climates, your kiwis will appreciate some light shade or dappled sunlight in the hottest part of the day.

Your newly transplanted kiwi vine should be watered often. Check young plants daily and water if the soil isn’t obviously moist. After the plant has transitioned, you can water more carelessly. Give mature plants a good soaking and then let them dry out for a few days.

A bit of mulch or some light manure is great for keeping hardy kiwis happy. Avoid fertilizers though, as the plant is easily overwhelmed buy rich soil.

Pruning Your Kiwi Vine

ImageParty /

Most kiwis won’t produce fruit their first season. By the second season, however, you should start seeing some delicious morsels. With careful pruning, each year will yield a more abundant harvest than before.

Pruning the long, gangly kiwi plant may seem intimidating, but kiwis are very forgiving. Late fall and early winter are ideal times for doing so. After the growing season, cut your plant back to a place where the stem is about 1/4 inch in diameter. If your vine didn’t produce enough well-sized branches, just cut it back by about 2 feet and hope for better growth next year.

First-year pruning focuses on building a strong foundation. You want to encourage straight growth and a good, basic framework. Concentrate on training the stem to grow straight along its trellis.

In later years, work on building strong side growth off of your main stem. Cut away branches that are twisting around other branches, they’ll end up choking part of your kiwi plant.

If you’re trellising your kiwi (and you really should be), encourage the plant to grow with its trellis. Keep it from wrapping around it and overwhelming its support structure. “On, not in” is a great motto while pruning. Your kiwi is growing on a trellis, not in one. Keep it following the right course.

Harvesting Kiwi Fruit

aimnotboy /

Hardy kiwi fruit don’t ripen all at once. Like tomatoes, they ripen gradually. You’ll know the fruit is ripe when they feel soft to the touch and are just noticeably fragrant. These kiwis can be harvested when ripe, or they can be harvested while still firm and allowed to ripen on the counter.

Depending on when the growing season begins in the spring, your hardy kiwis could ripen anywhere from July to November. They absolutely must be harvested before the first frost arrives. It’s essential to keep an eye on the fruit and the weather.

Kiwi fruit harvested before ripening last longer and taste just as sweet. Just make sure that you don’t harvest too soon. There’s a wide window of opportunity in kiwi harvesting, but if kiwi is harvested too early, it’ll have to ripen indoors. This will result in a dull flavor and a less juicy interior.

The best way to avoid this is to allow your kiwis to ripen on the vine as long as possible. Then, check a fruit or two before picking.

If you do want to harvest early, pick one kiwi and cut it open. Look at the seeds. If the seeds are black, the fruits can be picked, even if the fruit itself is still very hard. Black seeds indicate that the fruit is mature enough to finish ripening indoors.

Remember that fruit harvested when ripe won’t last long on the counter. You’ll have to eat it quickly!

Over-Wintering Your Kiwi Plant

TanteTati /

Surprisingly carefree in the winter, hardy kiwis can get by with minimal preparation.

After harvesting all the fruit you can find before frost, let your kiwi plant rest for a month before pruning. Prune back before the coldest winter weather hits. Up here, that would be late November or early December.

Prune gently, then mulch your kiwi plant with straw and manure. Just straw is fine too, but avoid heavy fertilizers as kiwis are sensitive to over-feeding. They do need a thick layer of mulch around the root base to winter well, so pile on the layers.

Try to spread the mulch as well, to keep the surrounding ground warm and mulch up the base of the plant.

In snowy climates, piling snow over the mulch layer actually adds additional insulation for the roots. Therefore, shovel some snow on top of your kiwis in the winter to keep the root base safe from that bitter winter air.

Not So Tropical After All

Bring a touch of the tropics to your garden, without all the hassle of building a greenhouse or moving to Hawaii.

Hardy kiwi plants are beautiful, graceful, and delicious plants that can make you feel as though you live in the tropics. With their delicate flowers and abundant fruits, they’ll transform your garden into a magical retreat. Plant them alongside hardy hibiscus plants and Chicago fig trees for a decadent escape from conventional cold-climate gardening.

With plants like these, who needs a vacation!

Kiwifruit 1: Why are they so fuzzy?

Kiwifruit is not covered in hairs. It’s covered in trichomes. And only if you’re talking about green Actinidia chinensis var. deliciosa. But, why? One answer is: pretty much to keep it from drying out. Another is: because it’s a polyploid from western China and was kind of chosen at random to be the most commonly grown kiwifruit, and they’re not all fuzzy. Those aren’t mutually exclusive answers. Put on your ecophysiology hats and grab a paring knife.

Think of fruit growth as a balancing act between ingoing and outgoing fluxes. When the balance is positive, fruits grow. When it is negative, they shrink—or shrivel. The main fluxes in question are carbon and water, which enter the fruit from the xylem and phloem of the plant vascular system. Water is lost mainly to the atmosphere via transpiration (evaporative water lost through stomata and other pores and from the skin surface). Keeping the ledger positive isn’t an easy job for a fruit. Hot, dry, and windy weather encourages transpiration and thereby increases the odds that a fruit will experience water stress. Excessive sunlight may cause sunburn. Fruits also need to avoid attack from pathogens and herbivores before the seeds within mature. A fruit’s skin—its cuticle and epidermis—is its first line of defense against abiotic and biotic threats. Some fruits resort to creative coverings to get the job done.

Here I’ll take a close look at the skin of kiwifruits. Why, exactly, are they so fuzzy?

A heart-shaped green kiwifruit (Actinidia chinensis var. deliciosa), covered in fuzzy trichomes

Functional fuzz

The short explanation for why kiwifruits are fuzzy is that they are covered with trichomes: hair-like extensions arising from the cell walls of the epidermis whose structure can vary widely. The trichomes covering kiwifruit are multicellular, and generally come in short and long varieties (1). Kiwifruit’s trichomes are also nonglandular, as opposed to specialized glandular trichomes that bear essential oils (see examples in our essays on lemon flavor and green walnut), or stinging trichomes, like those on nettle (Urtica spp.).

The fuzziest kiwifruit most of us will encounter is the widely commercially available green kiwifruit, cultivars of Actinidia chinensis var. deliciosa, which has bright green flesh when ripe (we’ll explore green fruit color in an upcoming post) and tough, inedible skin covered with coarse fuzz (trichomes). The length and density of trichomes actually varies within and across the 50+ species in the kiwifruit genus Actinidia (family Actinidiaceae, order Ericales; 2–4). For example, yellow-fleshed “golden” kiwifruit (A. chinensis var. chinensis), which is becoming increasingly commercially available, is covered less densely and with shorter trichomes than green kiwifruit (1). And if you’re especially lucky you might get your hands on tiny kiwiberries (Actinidia arguta), which have a hairless, thin, edible skin, much like a grape. This trichome variation is part of the longer explanation of why (some, most) kiwifruits are densely covered with trichomes, which is that trichomes help defend the fruit against adverse environmental conditions.

Just like any other would-be herbivore, you likely experience kiwifruit trichomes as an annoying impediment in your quest to access the fruit within. As to that fruit within, the botany (anatomy, breeding system) of kiwifruit is a bit tangential to this discussion of its trichome ecology (its relationship to the environment and other organisms), but as a hopefully useful aside, you can find the botany basics of kiwifruit in Figures 1 and 2 below.

Figure 1. Position of major vascular bundles (xylem and phloem) and structures in kiwifruit. Kiwifruit is botanically classified as a berry, a fleshy fruit that develops from a single ovary. The kiwifruit ovary is composed of numerous fused carpels. Each carpel bears its own style and stigma, creating a starburst pattern in the center of the pistillate flowers (see Figure 2 below). Those stigmas can persist through fruit ripening and remain visible at an end of ripe kiwifruit (shown here on A. arguta). The same goes for the tough sepals below the petals. Those many carpels contain chambers called locules, in which seeds develop. Septa divide locules and carpels within the ovary and are visible in a kiwi cut in cross section as pale white lines (shown here for A. chinensis var. deliciosa). The carpels radiate around the large, white central (axial) placenta, which is formed of homogeneous, large parenchyma cells and vascular tissue. The major vascular bundles in the fruit are also generally visible in cross section as translucent dots. Anatomy from Clearwater et al. (2012) and Guo et al. (2013).

Figure 2. All species in the kiwifruit genus (Actinidia) are climbing woody vines (lianas) that are dioecious, with separate staminate (male) and pistillate (female) flowers, usually borne on separate vines. The pistillate Actinidia flower (photo from Guo et al. 2013) in the photos shows multiple stigmas and styles arising from the fused carpels in the ovary (the pistillate flowers do make stamens but lack viable pollen). Each stigma/style provides an avenue for the pollination of the ovules in the locules of one of the fused carpels within the ovary. The stigmas are persistent and visible on ripe fruit.

Bugs, weather, or both

The nonglandular trichomes covering kiwifruits are similar to those creating fuzz on sundry other structures in various species: think of fuzzy leaves, stems, bracts, buds, inflorescences you may have seen. Despite the ease with which examples of fuzzy plant structures come to mind, it is not always straightforward to infer the function of that fuzz. Most of the function of glandular trichomes appears to be defense against herbivores and pathogens, mostly by way of the noxious chemicals that the glandular trichomes produce. By simply creating a physical barrier, defense might also account for some or all of the purpose of nonglandular trichomes. There is some evidence for that, at least for fuzzy leaves in some species (5–7). After incurring herbivore damage, for example, several species have been observed to increase the density or number of trichomes covering new leaves (8, 9). The primary function of fuzz-forming trichomes, though, may also be to help plants cope with stress from prevailing climatic conditions, and that is likely the case for the fuzzy fruits in question here. Keep in mind, though, that trichomes may serve more than one purpose, and I don’t know of any studies for any trichome-covered structure in which hypotheses regarding pests and weather have been tested simultaneously.

Persistent sepals on a green kiwifruit

Fuzzy logic

Fuzzy leaves and other structures are more well-studied than fuzzy fruits, but most evidence available points to broadly similar function of dense trichomes on both structures. The problem is, you can find trichome-covered plant structures in almost every environment on Earth where plants grow, and it seems that the primary function of the fuzziness varies across those many environments because the dangers to plants vary, too. Not all of the plants in a given spot will have obviously fuzzy parts, though, which is a clue that trichome density is only one plant characteristic that a plant species may have modified in order to live under the prevailing conditions. Trichome density, at least on leaves, too, is plastic: it varies in response to recent environmental conditions, including weather and herbivory, not just overall climate trends. That is, in a dry year, some plant species may increase trichome density, and we’ve already described how plant structures re-growing after herbivory may have higher trichome density.

Alpine Pedicularis lanata and Dryas, with woolly trichome-covered inflorescence and leaves, respectively (Chugach Mountains, Alaska)

It is likely that trichome density is idiosyncratic to individual plant populations (10), species, or lineages (11–13), and much work remains to piece together its evolutionary trends. In general, trichomes appear to moderate the ravages of various environmental stresses by affecting the temperature and humidity of air in the boundary layer at the plant surface (9, 14–16), or by reflecting excessive sunlight or ultraviolet radiation (17–21).

Some trichomes might act as umbrellas, repelling excess water (and perhaps fungal spores) from plant surfaces in overly wet environments (22), while in dry or foggy environments, trichomes might help with water uptake (23, 24) or humidity maintenance (25–30). In hot environments, trichomes may help cool the plant surface by reflecting sunlight, reducing the plant’s need to dissipate excess heat via evaporative cooling, and thereby reducing water loss (21). In cold environments, fuzzy trichomes act in part as an insulative blanket, warming the underlying structures. Think of the fuzzy bracts covering flower buds in magnolia and pussywillows (22, 31) emerging in the cool early spring.

From leaves to peaches to kiwifruit

Setting aside anti-herbivore or anti-pathogen roles that the fuzz-forming trichomes may play, a fuzzy specialized epidermis and cuticle appears to be one general strategy to avoid water loss or excessive heat and sunlight in xeromorphic plants, species with adaptations for tolerating sunny, dry environments (21). Sunny, semiarid conditions characterize many areas of especially western China, where both kiwifruit (2–4). and peaches were first domesticated (32).

Most of what we know about the function of fuzzy fruit surfaces comes from work on peaches, which are becoming something of a model organism for fuzz (25). The main function of those trichomes, as far as we understand it, is to help the peach avoid excessive water loss or sunburn (25). The hairs physically deflect hot sunlight and dry wind that would pull water away from the ripening peach and expose it to dangerous ultraviolet radiation. Trichomes therefore augment the water retention role of the wax-covered cuticle (25). The fuzz might also might make it more difficult for pathogens and pests to damage the fruit or seed, although this aspect his been less explored for peach (21, 25).

There is some evidence that kiwifruit trichomes also reduce desiccation. Golden kiwifruit was initially successfully commercialized alongside green kiwifruit in the mild, maritime climate of New Zealand. When golden kiwifruit was introduced into other regions of the world where green kiwifruits are commercially grown in hotter and drier conditions, such as California and Italy, the golden kiwifruits developed a shrivel disorder late in ripening, which is a failure of the plant vasculature to respond to sunny, arid conditions (33). Even when the irrigated vines themselves appeared healthy, the ripening golden kiwifruit lost water. Careful studies of water balance demonstrated that the cause was transpiration from the ripening fruit in excess of water inputs to the fruit from the vascular system (33). The hot, dry California environment simply forced the golden kiwifruit to lose more water than it did in cooler, more humid New Zealand, even though green kiwifruit ripened without issue in both environments (33). Specifically, the golden kiwifruit has a high surface conductance and transpiration rate compared with the green kiwifruit (33). Researchers confirmed that excessive water loss from the skin was the cause of the shrivel disorder in golden kiwi by conducting an experiment in which a plastic bag that increased the humidity of the air around the ripening fruit prevented the disorder (34).

I can think of two reasons why golden kiwifruit ripens less well in the golden state, which I’ll elaborate on below: (i) The trichome density of green and golden kiwifruits appears to be an adaptation to their respective environments of origin in different parts of China; and (ii) Commercial varieties of kiwifruits are especially close to their wild relatives, so we might expect high environmental fidelity for particular accessions.

Kiwifruit trichome density reflects domestication history and polyploidy

As a formal agricultural enterprise, kiwifruit domestication is only about 100 years old (3) and is still very much underway. The most popular commercial varieties are only slightly removed from natural populations of Actinidia (2, 3, 35, 36), and new varieties are being identified from the wild and improved continually (recently, for example, A. eriantha; 37). Thus, commercial kiwifruit is quite similar to its wild relatives (3).

Golden kiwifruit (A. chinensis var. chinensis) naturally occurs mostly in the southern and eastern parts of China, in the subtropical, mild and wet locations in the Hunan Foothills. Green kiwifruit (A. chinensis var. deliciosa) occurs mainly in the western provinces, on the higher, more arid, Yun-Gui Plateau (2).

Polyploidy (multiple sets of chromosomes, as opposed to diploid, one copy) is rampant in in A. chinensis across its range (2–4, 36). Polyploid populations arise when duplicated genetic material is retained in a single gamete instead of being split into multiple gametes, and those gametes with extra genetic material nonetheless go on to produce viable offspring. Polyploidy is common in plants and is an important source of genetic variation for crop development (35). The A. chinensis varieties with the highest ploidy levels are found in the highest and driest spots (2). Populations of both green and golden kiwifruit from arid and high-altitude regions of China tend to be both polyploid and hairier.

Progression of dominance from highly polyploid A. chinensis in arid western China to diploidy in the more moderate east, from (2): “The geographical distribution of 16 sample populations of Actinidia. A, The three steps of the Chinese topography are shown and the rectangle indicates the region in which the samples were obtained. B, Pie diagrams represent the proportion of ploidy races within each population. The colour spectrum of the map from blue to red indicates the altitude change.” I think the subspecies designation in the upper right corner here is misleading: all the hexaploid individuals in this study were var. deliciosa (very fuzzy green kiwifruit), and all the diploids were var. chinensis (less fuzzy golden kiwifruit).

Both polyploidy and increased trichome density (on at leaves if not fruit) have been positively correlated with the increased aridity and exposure to ultraviolet radiation typical of western China and high-altitude habitats in Actinidia (2, 3, 36, 38) and in some other taxa (39, 40). The Andean root vegetable maca is another example of a high altitude polyploid food plant. The most common variety of hairy green kiwifruit grown around the world, “Hayward,” is hexaploid (36), a polyploid with three copies of the genome (the ancestral state of Actinidia is diploid). All commercial hexaploid kiwfruit cultivars are green-fleshed, very hairy, and come from western China (36). Most commercial golden kiwifruit varieties are diploid, and therefore prone to less hairness and an eastern Chinese origin (36). The center of the ranges of most of the smooth-skinned kiwifruits overlaps with the highest incidence of diploid A. chinensis and slightly fuzzy golden kiwi (A. chinensis var. chinensis) in the relatively mild south- to central-eastern China (3), providing anecdotal evidence, at least, that trichomes aren’t necessary to prevent water loss in that more forgiving climate.

unpeeled, sliced kiwiberry (A. arguta)

More on peach vs. kiwifruit fuzziness

Katherine’s excellent essay on peach and nectarine genetics describes how changes in one gene ceases peach fuzz formation and turns the peach into a nectarine. While the mutant nectarines differ in many important respects from their peach progenitors, as far as I can tell, traits related to water loss or ultraviolet light avoidance have not yet been measured (41). Unlike with peaches and nectarines, we don’t know much about the genetic basis of trichome density in kiwifruit. We know that some genes are only expressed in fuzzy kiwifruits (42), and we know that all the non-fuzzy (glabrous) kiwifruit species are all in a single evolutionary clade (descendants from a single common ancestor; see our plant phylogeny page for a primer on these concepts), indicating that fuzzy fruit is the ancestral condition in Actinidia (43). Beyond that, though, there is obviously much work to be done to understand the genetic basis of fruit fuzziness.

Also, kiwifruit trichomes are multicellular, so they are a bit more complex than the single-celled trichomes of peach fuzz. If we infer that their function in preventing excessive water loss is similar, it begs the question of why peach produces simple, and thereby relatively cheap, trichomes, whereas kiwifruit produces more complex and therefore presumably more costly trichomes. Maybe simple trichomes wouldn’t do the job? Or the evolutionary capacity for one or the other types of trichomes simply wasn’t present? Much more work remains to be done on evolutionary pathways and selection pressures in trichomes.

The genomic (including ploidy) and genetic understanding of the characteristics that allow different fruit varieties to thrive in different environments is absolutely relevant to the production of fruit for human consumption. A plant can only breed with a compatible plant with the same ploidy level (see a good discussion of this in Katherine’s watermelon essay), so for kiwifruit, this affects the creation of hybrid lines in both the wild and on the farm, to produce desirable fruit that can thrive in different habitats. Reducing fruit hairiness is a target of kiwifruit breeding (3), but this effort will only be successful if the hairless fruits won’t shrivel in habitats where the vines supporting them otherwise thrive (as with the California-grown golden kiwi example).

Until that happy day of fuzz-less kiwifruit for all arrives, though, perhaps now it will be enough to have more food for thought while peeling.

References (below)

  1. Hallett IC, Sutherland PW (2005) Structure and development of kiwifruit skins. Int J Plant Sci 166(5):693–704.
  2. Li D, Liu Y, Zhong C, Huang H (2010) Morphological and cytotype variation of wild kiwifruit (Actinidia chinensis complex) along an altitudinal and longitudinal gradient in central-west China. Bot J Linn Soc 164(1):72–83.
  3. Huang H, Liu Y (2014) Natural hybridization, introgression breeding, and cultivar improvement in the genus actinidia. Tree Genet Genomes 10(5):1113–1122.
  4. Liu YF, Li DW, Huang H (2011) Cytotype variation in the natural populations of actinidia chinensis complex in China. Acta Horticulturae, pp 157–162.
  5. Dalin P, Ågren J, Björkman C, Huttunen P, Kärkkäinen K (2008) Leaf trichome formation and plant resistance to herbivory. Induced Plant Resistance to Herbivory (Springer Netherlands, Dordrecht), pp 89–105.
  6. Agrawal AA, Spiller DA (2004) Polymorphic buttonwood: Effects of disturbance on resistance to herbivores in green and silver morphs of a Bahamian shrub. Am J Bot 91(12):1990–1997.
  7. Hanley ME, Lamont BB, Fairbanks MM, Rafferty CM (2007) Plant structural traits and their role in anti-herbivore defence. Perspect Plant Ecol Evol Syst 8(4):157–178.
  8. Traw MB, Bergelson J (2003) Interactive effects of jasmonic acid, salicylic acid, and gibberellin on induction of trichomes in Arabidopsis. Plant Physiol 133(3):1367–1375.
  9. Atala C, Gianoli E (2009) Effect of water availability on tolerance of leaf damage in tall morning glory, Ipomoea purpurea. Acta Oecologica-International J Ecol 35(2):236–242.
  10. Sandquist DR, Ehleringer JR (2003) Population- and family-level variation of brittlebush (Encelia farinosa, Asteraceae) pubescence: Its relation to drought and implications for selection in variable environments. Am J Bot 90(9010):1481–1486.
  11. Arunprakash S, et al. (2014) Studies of Trichome in Five Species of Asteraceae. Int J Adv Interdiscip Res Sai Yaashitha Res Publ Int J Adv Interdis Res. Available at: http://ijaidr.co.in/files/Arun Prakash 1-4.pdf .
  12. Serna L, Martin C (2006) Trichomes: different regulatory networks lead to convergent structures. Trends Plant Sci 11(6):274–280.
  13. Agrawal AA, et al. (2009) Phylogenetic ecology of leaf surface traits in the milkweeds (Asclepias spp.): Chemistry, ecophysiology, and insect behavior. New Phytol 183(3):848–867.
  14. Sletvold N, Agren J (2012) Variation in tolerance to drought among Scandinavian populations of Arabidopsis lyrata. Evol Ecol 26(3):559–577.
  15. Shibuya T, Itagaki K, Ueyama S, Hirai N, Endo R (2016) Atmospheric humidity influences oviposition rate of Tetranychus urticae (Acari: Tetranychidae) through morphological responses of host Cucumis sativus leaves. J Econ Entomol 109(1):255–258.
  16. Kessler M, Siorak Y, Wunderlich M, Wegner C (2007) Patterns of morphological leaf traits among pteridophytes along humidity and temperature gradients in the Bolivian Andes. Funct Plant Biol 34(11):963–971.
  17. Karabourniotis G, Bornman JF (1999) Penetration of UV-A, UV-B and blue light through the leaf trichome layers of two xeromorphic plants, olive and oak, measured by optical fibre microprobes. Physiol Plant 105(4):655–661.
  18. Karabourniotis G, Fasseas C (1996) The dense indumentum with its polyphenol content may replace the protective role of the epidermis in some young xeromorphic leaves. Can J Bot 74(3):347–351.
  19. Ehleringer J (1982) The Influence of Water-Stress and Temperature on Leaf Pubescence Development in Encelia-Farinosa. Am J Bot 69(5):670–675.
  20. Ehleringer J, Mooney HA, Gulmon SL, Rundel PW (1981) Parallel Evolution of Leaf Pubescence in Encelia in Coastal Desert of North and South America. Oecologia 49(1):38–41.
  21. Skelton RP, Midgley JJ, Nyaga JM, Johnson SD, Cramer MD (2012) Is leaf pubescence of Cape Proteaceae a xeromorphic or radiation-protective trait? Aust J Bot 60(2):104–113.
  22. Yang Y, Korner C, Sun H (2008) The ecological significance of pubescence in Saussurea medusa, a high-elevation Himalayan “woolly plant.” Arct Antarct Alp Res 40(1):250–255.
  23. Vitarelli NC, Riina R, Cassino MF, Meira RMSA (2016) Trichome-like emergences in Croton of Brazilian highland rock outcrops: Evidences for atmospheric water uptake. Perspect Plant Ecol Evol Syst 22:23–35.
  24. Yang Q, et al. (2010) Research progress on water uptake through foliage. Acta Ecol Sin 30(3):172–177.
  25. Fernandez V, et al. (2011) New Insights into the Properties of Pubescent Surfaces: Peach Fruit as a Model. Plant Physiol 156(4):2098–2108.
  26. Fernández V, Khayet M (2015) Evaluation of the surface free energy of plant surfaces: toward standardizing the procedure. Front Plant Sci 6:510.
  27. Schreuder MDJ, Brewer CA, Heine C (2001) Modelled influences of non-exchanging trichomes on leaf boundary layers and gas exchange. J Theor Biol 210(1):23–32.
  28. Brewer CA, Smith WK, Vogelmann TC (1991) Functional interaction between leaf trichomes, leaf wettability and the optical properties of water droplets. Plant Cell Environ 14(9):955–962.
  29. Brewer CA, Smith WK (1997) Patterns of leaf surface wetness for montane and subalpine plants. Plant Cell Environ 20(1):1–11.
  30. Lusa MG, Cardoso EC, Machado SR, Appezzato-da-Glória B (2015) Trichomes related to an unusual method of water retention and protection of the stem apex in an arid zone perennial species. AoB Plants 7(1):plu088-plu088.
  31. Tsukaya H, Tsuge T (2001) Morphological adaptation of inflorescences in plants that develop at low temperatures in early spring: The convergent evolution of “downy plants.” Plant Biol 3(5):536–543.
  32. Li H-L (1968) The Origin of Cultivated Plants in Southeast Asia 1. Econ Bot 24(35):3–19.
  33. Clearwater MJ, Luo Z, Ong SEC, Blattmann P, Thorp TG (2012) Vascular functioning and the water balance of ripening kiwifruit (Actinidia chinensis) berries. J Exp Bot 63(5):1835–1847.
  34. Thorp TG, et al. (2007) “Hort16A” fruit beak end softening and shrivelling in California. Acta Horticulturae, pp 389–396.
  35. Li D, et al. (2014) Genetic diversity in kiwifruit polyploid complexes: Insights into cultivar evaluation, conservation, and utilization. Tree Genet Genomes 10(5):1451–1463.
  36. Li D, Zhong C, Liu Y, Huang H (2010) Correlation between ploidy level and fruit characters of the main kiwifruit cultivars in China: Implication for selection and improvement. New Zeal J Crop Hortic Sci 38(2):137–145.
  37. Wu YJ, et al. (2009) Characteristics of “white”: A new easy-peel cultivar of actinidia eriantha. New Zeal J Crop Hortic Sci 37(4):369–373.
  38. Liu Y, Liu Y, Huang H (2010) Genetic variation and natural hybridization among sympatric Actinidia species and the implications for introgression breeding of kiwifruit. Tree Genet Genomes 6(5):801–813.
  39. Guo W, et al. (2016) Divergence in Eco-Physiological Responses to Drought Mirrors the Distinct Distribution of Chamerion angustifolium Cytotypes in the Himalaya–Hengduan Mountains Region. Front Plant Sci 7:1329.
  40. Karl R, Koch MA (2013) A world-wide perspective on crucifer speciation and evolution: Phylogenetics, biogeography and trait evolution in tribe Arabideae. Ann Bot 112(6):983–1001.
  41. Wen I, Koch KE, Sherman WB (1995) Comparing Fruit and Tree Characteristics of Two Peaches and Their Nectarine Mutants. J Am Soc Hortic Sci 120(1):101–106.
  42. Kim SC, et al. (2004) Characterization of RAPD fragment unique to species with hairy fruit skin in the genus Actinidia. J Plant Biol 47(3):210–215.
  43. Huang H, Li Z, Li J, Kubisiak TL, Layne DR (2002) Phylogenetic Relationships in Actinidia as Revealed by RAPD Analysis. J AMER SOC HORT SCI 127(5):759–766.
  44. Guo X-M, Xiao X, Wang G-X, Gao R-F (2013) Vascular anatomy of kiwi fruit and its implications for the origin of carpels. Front Plant Sci 4:391.

After I wrote my first blog post about Black Widow spiders, I started having a little trouble coming up with my next idea. There’s so much around me that I don’t know about, but so little of it is something I would be interested to know. Fortunately for me, I have a four year old. Little kids are always asking questions, and mine is usually asking two at the same time. We were driving back home when she asked, “Mom why are kiwis and edamame so hairy?” Good question kiddo, I don’t know. And that became the next topic of my blog.

If you’ve ever eaten soybeans (or edamame) from the pod, you’ll notice the pods are covered in tiny little hairs. That’s pretty unique to them because if you look at sugar snap peas, snow peas, or even green beans they have very smooth skin. The Chinese, who have been eating edamame since the 3rd century A.D., call them mao dao which means hair bean. Pretty fitting!

And it seems that China has a thing for hairy produce because the kiwi fruit originates from China. In fact, it’s their national fruit! Bet you thought kiwis were from New Zealand. Nope, they were originally called the Chinese Gooseberry, but when New Zealand started growing the fruit commercially, they changed the name to kiwi (after their national bird). Sneaky New Zealanders!!

Wow, you’ve already learned so much and I haven’t even answered the question yet. So why are they so hairy? Well for two reasons. First, to keep bugs away. The little hairs annoy the bugs and help to keep the plant bug free. Kind of like those spikes they put on the window air-conditioning units to keep birds from nesting/hanging out there. Nobody wants bird poop in their air conditioner!

Second reason is to help the fruit retain moisture. The hairs do this in two ways. They collect the dew in the morning so that helps keep the fruit moist. And, they act like a barrier, keeping the moist air close to the fruit. Think of the hairs like a little shirt for the kiwi. Your shirt keeps warm air close to your body and the hairs keep the moist air close to the fruit. Cool huh?

So that answers the question, but I did find couple more cool things about kiwis (or Chinese Gooseberries) that I thought I’d share with you. The skin of the kiwi is totally edible! If you don’t like the hairs….you might be a bug….just kidding. If you don’t like the hairs, just rub them off, rinse your kiwi and chow down. And for all of you chefs out there, the kiwi contains a very unique enzyme called Actinidine. This enzyme is excellent at breaking down protein (pineapple is the same way….just a different enzyme). So if you want to tenderize your meat, you can rub the fruit side of the skin, or a few slices of kiwi, over the meat, wait 20 minutes and then you’re ready to go.

Now you have more interesting facts to share the next time you find yourself at a cocktail party. And now I can finally answer my daughter’s question about edamame and kiwi. If you have something you’d like to learn about (or something your kids have been asking about), feel free to leave some topic suggestions in the comments section! And you can follow me on Instagram for little snippets at AnEmptyEncyclopedia

The Kiwi To My Heart

Everything you need to know about kiwifruit, including different kiwi varieties, storage tips, kiwi nutrition information, and more!

For the next two weeks, we’ll be exploring the bright green, vitamin C-packed world of kiwifruit (a.k.a kiwi) (a.k.a. Chinese gooseberries) (P.S. does anyone even call them Chinese gooseberries?) Native to China, these peculiar fruits were first commercially grown in New Zealand, where they picked up the name “Kiwifruit”, and have since made their way around the globe and stampeded their way into my kitchen for this week’s ingredient spotlight.

Kiwis are absolutely packed with vitamin C (even more than an orange!) They’re also pretty acidic, making them a unique cooking ingredient for their ability to tenderize and digest proteins. This week we’ll be making a few sweet things, but also a savory kiwi infused dish that I’m so in love with and can’t wait to share (hint: TACOS). Read on for all the kiwifruit learns, and stay tuned for the recipes later this week!

Varieties of kiwifruit

  • Fuzzy kiwis: This family of kiwis includes the variety you’re probably most used to eating, being about the size of a large egg with a fuzzy brown exterior and bright green fruit.
  • Kiwi berries: These are the size of a grape, with a fuzzless, smooth skin and the same bright green interior.
  • Golden kiwi: These have a golden flesh that’s sweet and a bit tropical tasting. Due to a shorter shelf life, these are not as commercially available (though I’ve spotted them from time to time in my local grocery!)

How to select and store kiwifruit

Choose fragrant, slightly soft fruits. Harder fruits will be more astringent and sour. Kiwis will continue to ripen after you buy them, so if you want to ripen them faster, store them in a paper bag at room temperature. To slow down ripening, store your kiwifruit in the fridge.

Kiwifruit nutrition information

per 1 cup fresh kiwi (177 g)

  • Calories: 108
  • Carbohydrates: 26 g
  • Fiber: 5 g, 21% Daily Value (DV)
  • Protein: 2 g
  • Fat: 1 g
  • 237% DV of Vitamin C: A water-soluble vitamin that acts as an antioxidant to fight against potentially damaging free radicals (molecules with unshared electrons that float around wreaking havoc) and an important cofactor in collagen synthesis.
  • 89% DV of Vitamin K: A fat-soluble vitamin that allows for activation of enzymes in the clotting cascade, which is responsible for blood clotting. Also builds bone by modifying osteocalcin so that it may bind calcium, thus building the bone matrix.
  • 13% DV of Vitamin E (a.k.a Tocopherols and Tocotrienols): A fat-soluble antioxidant that fights against potentially damaging free radicals from reacting with oxygen when fat is metabolized.
  • 11% DV of Folate: (Vitamin B9): A water-soluble vitamin that helps make DNA & RNA and metabolize amino acids.

Growing Hardy Kiwi

Imagine a fruit with kiwi flavor, but sweeter, grape-sized and fuzz-free. Such a thing exists and we can grow it in our backyards with ease. Not surprisingly, this fruit is called hardy kiwi.

“People really like the taste of kiwi. It’s a different fruit. And with hardy kiwi, you can just pop it in your mouth without peeling because it doesn’t have the fuzzy skin,” said fruit grower David Garretson of Beechwood Orchards in Biglerville, PA.

The kiwi we are most familiar with is native to China and won’t tolerate temperatures lower than 10 degrees. Hardy Kiwi can be grown as far north as zone 6. Garretson said that a late spring cold spell can damage some tender new growth but hardy kiwi grows so quickly, it can compensate for the loss.

Hardy kiwi is an excellent fit for backyard growing. The vine grows very quickly, is attractive and, importantly, it’s not super fussy. “Kiwi doesn’t take a lot of spraying,” said Garretson. Like raspberries, strawberries and blueberries, kiwi does not require the treatment regiment that might be required to produce vigorous and cosmetically appealing stone fruits like peaches.

The ornamental appeal of hardy kiwi helps maximize space in home landscapes by doing the double-duty of looking good while producing fruit. Reddish vines with rich green leaves and fruit are kiwi’s decorative qualities. Our Kiwi, Hardy Red, adds extra late summer appeal as the fruit ripens red. Consider growing hardy kiwi on a pergola or trellis in a sunny spot in your ornamental garden. One plant can grow 15 feet in one year, so it will quickly fill-in and cover the structure.

One plant will get large quickly but two plants – a male and a female – are required to make fruit. Our sets include one of both. If you’d like more plants or would like to try other varieties, you can often purchase only females because you only need one male for approximately every six females. The age of the plants has an impact on fruiting.

Hardy Kiwi takes a few years to produce fruit. Depending on the age of the vines you purchase, it could be one to three years before fruit is made. Yields will increase after the first year. Male plants need to be older than the females to perform their function.

“Just as with people, they always say females mature more quickly,” said Garretson.

Like many fruits, hardy kiwi needs full sun and consistent moisture to thrive. Give your kiwi rich and well-drained soil and you’ll be rewarded with vines that romp and sweet fruit. Kiwi does not like wet soil or drought. Roots can be damaged if the roots are too wet. Drought will stress the plant and effect the size of the fruit. Prolonged lack of water can cause fewer blooms early in the season and fruit to drop before it’s ripen later in the season. Deep soakings rather than constant shallow watering during dry spells will help produce the best fruit.

Support is also important to kiwi. Garretson suggest starting out by staking the vine, then install a trellis to support the vine. Typically, kiwi is grown on T-shaped structure several feet off the ground for ease of picking. Create a trunk by pruning off laterals from the main vine in the dormant season along the vertical part of the T structure. Gently direct the main vine to the top of the T. Attach vines to supports to prevent breakage.

Once kiwi is mature enough to make fruit, you’ll notice that the fruit reach full-size by midsummer. Kiwi won’t ripen to its full sweetness until late summer – sometimes into September. Kiwi will continue to ripen off the vine, and will keep longer if picked just a bit before ripe. If picked too soon, the full sweetness won’t develop. To test, pick a few, allow them to ripen on a counter or in a window sill for a few days. If the kiwi becomes sweet and soft, it’s time to harvest. Storing kiwi in a refrigerator will keep them from ripening. Take out and ripen kiwi as needed.

Kiwi that’s ripened on the vine is delicious, too, but it won’t store as long. All kiwi should be picked before the first frost.

Consider adding hardy kiwi to your home garden. The vine is hearty, decorative and extremely long-lived. The fruit is fuss and fuzz-free, tasty, unique and stuffed-full of vitamin C. It’s an adventure to add to your garden.

Hardy Kiwi

Have you tasted these remarkable miniature kiwis yet? Every bit as delicious as the larger, more familiar fuzzy kiwi, hardy kiwis are much easier to grow and eat (skin and all). And just about every home gardener in North America can grow them.

Hardy kiwi is a catchall term for types of kiwis (Actinidia) that, when dormant, can survive temperatures as low as -40oF (USDA Hardiness Zone 3). These beautiful, vigorous natives of Russia, China, Japan, and Korea have deep green leaves and long whiplike vines that can grow as much as 20 feet in a season. In the wild, they may climb 50 feet or more into treetops.

The fruits, somewhat larger and rounder than grapes and with a more opaque green skin, hang in long, heavy clusters. Like fuzzy kiwis, they have soft flesh with small, black, crunchy seeds. They taste sweeter than fuzzy kiwis and don’t require peeling. Hardy kiwis are not common in markets because they don’t ship very well. But you might notice them sold in specialty markets as “baby kiwis.”

Where Do Hardy Kiwis Grow?

The short answer is, just about everywhere. Since hardy kiwis are cold tolerant but don’t require much winter chill to set fruit, most have a wide growing range — from Florida to Massachusetts and San Diego to Vancouver — anywhere temperatures stay above -25oF (zone 4). In colder parts of this range, plants need protection during occasional false springs, when a brief warm period induces leaves and shoots to sprout, only to be set back in the cold snap that follows. When that happens, the year’s crop will be pretty much wiped out.

If you live where winter temperatures dip below -25oF (zone 3 and colder parts of zone 4), you have two options. You can either grow the hardiest of the hardy kiwis, (A. kolomikta) ‘Arctic Beauty’, or grow any of the hardy species in 15-gallon pots in a greenhouse. Greenhouse-grown plants should fruit as long as they receive at least 100 hours below 45° F during the dormant season. Hardy kiwis require considerable amounts of water during the growing season, so they may not be well suited to drought-prone areas.

How to Grow Hardy Kiwis

If you prefer to plant bare-root, buy and plant hardy kiwis in winter or early spring, when you would any other bare-root fruit. In cold-winter areas, plant after all chances of frost have passed, from spring until midsummer. In areas with long growing seasons, plant hardy kiwis anytime, but do avoid the hottest parts of summer, when transplant stress is high.

Hardy kiwis must have strong vertical support. In their native forests, these heavy vines climb trees. In a home garden, they require a sturdy structure such as a patio overhead or a trellis with 4-by-4 supports.

Kiwis are dioecious, meaning you need to grow male and female plants in order for the female plants to set fruit. A single male will pollinate at least eight females. Space plants about 12 feet apart. If space is limited, place both a male and a female plant in one planting hole, or grow (A. arguta) ‘Issai’, the only self-fertile variety.

For A. arguta, A. cordifolia, and A. purpurea, select a spot with good drainage and at least half a day of sun. A. kolomikta ‘Arctic Beauty’ requires at least half a day of shade.

Hardy kiwis need rich soil. Generally, about 10 pounds of compost or manure per plant, in both early and late spring, is enough. However, if growth seems to lag, or if leaves are pale, supplement with a pound of soy or cottonseed meal per plant in late spring or early summer.

Growers have different fertilization schemes. Roger Meyer, a commercial grower in southern California, applies half of his plants’ yearly fertilizer allotment in late winter and the rest in monthly applications through July. Michael McConkey, who grows and sells hardy kiwi at his nursery in Virginia, fertilizes twice a year. He applies a third of each plant’s yearly allotment before spring growth starts and the rest after fruit sets.

Pruning. Hardy kiwis are long-lived. Careful and rigorous pruning is essential to create strong and productive plants. In their native forests, these plants put most of their energy into climbing to reach the sunlight at the top of the trees. In your garden, however, you want them to direct that energy into making fruit. You need to prune often, once every few weeks during the growing season. As one grower notes, “You can’t overprune a kiwi.”

Your goal is to create an umbrella-shaped plant. In the first year, limit each plant to one vertical shoot, and direct that shoot to the top of its support. That shoot will become the plant’s trunk. Wire or tie it loosely to the support.

In the first dormant season, prune each vine back to the top of its support.

In the second growing season, select two strong side branches near the top of the trellis and train them horizontally along the support. In the second dormant season, prune the side branches back to 1 to 2 feet long (12 to 18 buds on each). New branches will sprout from these side branches and become next year’s fruiting wood.

From the third year on, prune female kiwis in the dormant season so that fruiting branches are at least 6 inches apart along the main branches. Cut out any dead or weak wood, and all tangled branches. Cut off branches that reach the ground or are so close that their fruit clusters could reach the ground.

In cooler areas, prune males back hard in summer. Prune as often as necessary thereafter to keep them tidy and to prevent them from overtaking the female vines. Restrict pruning to spring and fall in hot climates because bare branches are susceptible to sunburn. Whenever you prune, be sure to leave some of the previous year’s wood so the plants flower and produce pollen.

Vines have a tendency to bleed if pruned too late in the dormant season, so do dormant pruning in the dead of winter.

Harvest

Most hardy kiwis take about three years to bear fruit, though ‘Arctic Beauty’ and ‘Issai’ often bear the first year after planting. Depending upon your region, most ‘Arctic Beauty’ fruits ripen in early to mid-August, while fruits of the others ripen from late August through mid-October. Fruits are picked hard-ripe, then allowed to soften off the vine, like avocado and fuzzy kiwi.

Starting in late August, pick a few fruits and let them ripen on a windowsill or in a paper bag. Taste them when the flesh is soft and the seeds are black. If they don’t ripen, wait several weeks and then test a few more fruits. When you notice the first fruit softening on the vine, pick all the fruit. Store hard-ripe fruit in airtight plastic containers or sealed bags in the refrigerator. Take out a few at a time to ripen. Eventually, all of the fruit on the vine will soften, but if you wait that long, you will have an overwhelming harvest of fruits that will last only a short time. Regardless of when you start to harvest, be sure to pick all the fruits before the first frost.

In Russia, hardy kiwis are made into jam, but they’re also delicious simply sliced in half and drizzled with fresh cream.

Hardy Kiwis for Home Gardeners

Actinidia arguta — Zones 5 through 10. Mature plants produce up to 100 pounds of fruit per season. Pest- and disease-free.

‘Dumbarton Oaks’ — Zones 5 through 8. Excellent flavor and early ripening.

‘Issai’ — Zones 6 through 10. Only self-fertile variety (a male pollenizing plant is not needed). Fruits the first year after planting. Medium-sized green fruit. Susceptible to spider mites in hot, dry climates.

A. cordifolia — Zones 5 through 10. Perhaps the sweetest of all and the first to ripen. It has been less successful in the Pacific Northwest.

A. kolomikta ‘Arctic Beauty’ — Zones 3 through 8. Best suited to short-season and cold-winter areas. Compared to A. arguta, plants are smaller and more delicate; fruits are smaller and ripen earlier. Fruits first year after planting. Plant where it receives partial to full shade. Leaves of male plants start the season deep green, then paint themselves with splashes of white and pink.

A. purpurea ‘Hardy Red’ — Zones 5 through 10. Vigorous vine; oblong red fruit is sweet with a bit of tartness.

Nan Sterman is a gardener and writer who lives in Olivenhain, California.

Care Guide

Kiwi Care Guide
~~
What Can’t Kiwi Fruit Do?
In what is believed to be one of the first papers published from China on Kiwi, Liang Boo adds exciting new possibilities for this famous fruit. The fragrant flower is rich in nectar and also provides a good base for the production of perfume.
The leaves contain starch protein, vitamin C and various other nutrients and make good pig feed. On using kiwi fruit for herbal medicines, he says it has proved effective in reducing fever, improving urination, dispersing exbavastated blood, stimulates blood circulation, steeping up milk excreting in nursing mothers, and relieving inflammation.
In some places, nursing mothers drink the liquid from the boiled root, plus a sweetener to promote lactation. And sufferers from boils, contusions or sprains are often given mashed root for external application.
The roots can be processed into an insecticide which is especially effective in killing such insects as rape and tea caterpillars, rice borers, aphids, cabbage worms and paddy rollers.
The stalk of the kiwi is rich in glue, which is obtained simply by soaking it in water. The glue is used in construction materials, road pavings, and a protective covering for walls. The glue is also an important ingredient in the manufacture of wax paper and Xuan paper, a high – quality paper used in traditional painting and calligraphy.
Hardy Kiwi
Hardy Kiwi is a new fruit. They are delightful to eat, sweet, with an unmistakable kiwi flavor. The plants are vigorous, hardy and not prone to disease and insect imbalance. They are dual purpose for landscape and nutrition, and the fruits keep well is storage. The vines are long lived. The Actinidia arguta at Dumbarton Oaks in Georgetown, Washington D.C.. were planted in 1920. The female vine fruits annually.
The fruits are not only used fresh, they can be dried, made into a sherbert and prepared in a variety of other ways. The hardy arguta fruit is smoothed skinned and green. It can be eaten whole. It’s sugar content is very high. Test at the Virginia Research Station averaged 17.7 Brix. Tests of the store bought kiwis (A. deliciosa) averaged 13.2 brix.. To judge how sweet 17.7 brix is , grapes to be dried for raisins should have a reading of 18 brix. The fruits are about the size of a small plum. When eating the fruit, the seeds are almost undetectable.
The arguta prefer somewhat moist and rich soil. Under suitable conditions they grow rapidly, fruit abundantly and bear early in life. Arguta’s will tolerate infertile soils, but will not tolerate flooding of soils of poor drainage. Once established they are very tough and adaptable. I have seen established vines in Rochester New Hampshire, Geneva New York, Washington D.C. and Virginia Beach Virginia. We have plants producing as far south as Miami. Argutas are excellent for covering walls, trellises, arbors, pergolas, tall stumps and the like. They can be grown over chicken coops and on chicken yard fences. They grow well in sun or shade.
Members of the genus Actinidia are natives of Eastern Asia. While several species are found in Japan, Manchuria and Korea. In the wild the vine intertwines through trees or grows in tangled masses in the open. They can reach a height of 40′.
Hardy Kiwis are alternate leafed. Their leaves in size and shape resemble the leaves of an apple tree. Flowers open in late May on new shoots grown from the previous season’s spur growth. Spurs are short branches with close internodes of less than two inches as compared to the main vine which has 3″ to 5″ internodes. The flowers are small and white with a lily of the valley fragrance. Individual plants are dioecious (male and female flowers are produced on separate plants). The West’s realization of this plant comes rather late. Where it naturalizes people have used it for many years. Distribution outside of its native habitat began around 1847. In the 1900’s collections were secured in England, France, the U.S. & new Zealand.

Hardy Male Kiwi Blooms
Female Blooms on Hardy Kiwi

Female Fuzzy Kiwi Flower

Pollination
Since kiwi fruit is a dioecious plant, that is, it produces male and female flowers on separate vines, both a male and female vine are required for fruit production. For best pollination 1 male for every 5 females. Size of a fruit depends, not only on good growing conditions and pruning, but also on the number of seeds that have been fertilized. Kiwi fruit vines should be considered tender and drought – sensitive until they are well established. Hardy Kiwi are heavy producers. As much as 150 lbs of fruit can be obtained from one female plant.
Growing Instructions
When planting space the plants at least 10ft apart. Plant the vines 10-20ft apart in the row, depending on trellis type & cultivation technique(ie.tractor etc.) Rows are commonly shallow cultivated or mulched. The nutritional requirements of A. arguta have not been well researched, but general recommendations have evolved. Fertilizer should be minimal or none at all at planting. Keep grass & seeds away and do not let the plants dry out the first year.. On established plants apply fertilizer twice per year with approximately twice as much applied before new growth as is applied after fruit set in June. Increase the rate of 1/2 lb. on newly planted vines to three lbs per plant by the 3rd year. These larger amounts should be well distributed over the entire root system to prevent root injury. A. arguta has few pests. Arguta roots are fleshy and can be injured by nematodes. Fuzzy Kiwis are best planted in rows north to south to prevent sun damage on the trunk of the vine. Winter damage like this can injure the plant so that it has to resprout from the roots.
Build trellises before or soon after planting to accommodate the rapid growth of plants. These can be similar to grape trellises but must be strong., Posts should be 4″ to 6″ diameter to support plant and fruit weights and 8ft to 9ft long. A post should be set 2ft to 3ft deep to prevent winds from tipping the row over. Run 8 to 12 gauge wire, at 6ft high. The wire allows vines to grow with easy access to fruits hanging from the underside. Be sure the trellis is sturdy. A common failure is the construction of inadequate trellises for supporting the weight of heavy fruit crops. A “T” trellis can be made from this system, which provides more area for the vine.
Train the 1st years growth to go up a stake. Side shoots can be pinched terminally so only 1 or 2 vigorous stems reach the 6ft mark. These stems will be trunks in a few years. Train later growth along the wires to form permanent arms. Branching extends outward from these arms and supports spurs from which flowers and fruits develop. The vigorous A.arguta (Hardy Kiwi) requires special pruning practices, which includes both summer and winter pruning (but mostly summer). For summer pruning, rub off basal suckers and strong vertical growth when they are only a few inches long,.(You’ll know the strong vertical growth – it clips along @ 2 ft per day). Waiting until unwanted shoots are several feet long before removing them results in unnecessary weakening of the plant. After a framework is established all the new growth coming from the arms can be pinched easily. The general rule of thumb is – pinch new 8″ growth back to 4″. That 4″ will elongate again in a few weeks, pinch it back to 4″ so in all there is 4″ of growth from the first pinching and 4″ from the second etc… this is how spurs are made. The objective of winter pruning is to balance fruit production with vegetative growth. Preferred limbs for removal are the three year old fruiting branches (those which have finished their third year of fruiting), damaged wood and the tortuously twining current years growth. Shorten the remaining current year’s limbs from the permanent arms sufficiently so that when laden with fruit they will not touch the ground. Branches with short internodes (spurs). These will bear flowers and fruit and should not be removed. Kiwi fruits reach mature size by mid-summer, but they require the remaining season to develop their mature texture and flavor. Determine full maturity by picking a fruit, allowing it to soften for a few days and tasting it for favorable flavor. When suitably sweet and flavorful, pick all fruits and refrigerate them until a few days before they are needed. Removal from refrigeration initiates softening and the development of the kiwi’s final sweetness and flavor. Kiwi may also be picked off the vine when they become soft for fresh eating. In favorable weather, the unpicked fruits will dry on the vine. Once permanent cordons are established, a kiwi vine must be pruned throughout its lifetime in order to maintain it’s form, contain its size, and most importantly, maximize its fruit production By pruning to provide a constant turnover of fruiting laterals, this training system can be maintained and productive for 60 years or more. Male kiwi vines can be trained and pruned in the same manner as female vines.


Mature Hardy Kiwi Vines
Hardy Kiwi growing up a brick wall

Crown & Root Rot on Kiwis
Phytophthora crown and root rot causes the kiwi plant to develop poorly and can cause the plant to die. Infected plants have small chlorotic (yellow) leaves: the terminal growth may die back, or be stunted. The first signs of root stress is when young tender ends of new growth-wilt; blacken. Infected plants will suddenly collapse during hot weather. Decayed tissue is found at the soil line. The infection can be observed at the soil line by removing or peeling the tissues away from the trunk or primary roots. Newly infected areas will have brown streaks. Older infections will be entirely brown and extend high up the trunk and far down into the primary roots. Healthy tissue will have cream or white colored tissue and sometimes the green band or ring of the cambium layer is seen. Phytophthora fungi require water saturated soil to infect a plant. Some species of Phytophthora prefer warm soil in the fall and spring to spread. Other Phytophthora prefer cold water. Some seek feeder roots, others go to large roots and move up the trunk.
These conditions are most prevalent in heavy soils with poor drainage above impervious layers that are just below the surface and low areas in the field where surface and underground water collects. Frequently crown and root rot will occur where the irrigation emitter continually releases water near the base of the plant. So, never plant in wet soil locations.

Leave a Reply

Your email address will not be published. Required fields are marked *