To get your Asparagus bed started you will want to select an area of your garden that can be left alone for many years. Because, unlike most other vegetables, Asparagus plants can live a long, long time.
Asparagus should be planted in soil that is deep with organic matter. Plants should be 12 to 18 inches apart in rows that are 3 feet apart. Plant the potted plants at ground level and not in a trench like you would a bareroot crown. Asparagus plants will spread horizontally along the ground as the years go by. If you plant them too close together they will crowd each other out.
As the plants get older the spears will get thicker. It will be the third year before you get any kind of real harvest. Only harvest about half the first few years so the plant can produce energy to spread. No spears, no spreading!
Spears should be harvested by bending near the ground and snapping. This is the best way to avoid damaging other spears not yet ready for harvest.
Be sure to keep your Asparagus bed weed free and fertilized well. In the fall, cut all ferns back to the ground and clean up fallen debris. Remove any plants that make berries (pretty rare). Apply a 2 to 3 inch layer of compost over the bed. This will help to suppress weeds that germinate in the spring.
A mature asparagus plant can produce between 1/2 to 3/4 of a pound of spears. One person who really likes asparagus can use about 20 plants all their own!
Yummy Asparagus recipes!
- Can You Grow Asparagus from Seed?
- Saving Asparagus Seed
- Growing Asparagus from Seed
- Transplanting Asparagus Seedlings
- How Long Until Harvest?
- Asparagus Plants
- How to Plant Asparagus in the Fall
- How Long Can Asparagus Crowns Be Stored?
- Do Asparagus Plants Need to Be Covered From Cold Weather?
- How Many Asparagus Can Be Planted Per Square Foot?
- When to Plant Asparagus in Florida
- Time Frame
- How Many Asparagus Grow on a Single Plant?
- Bed Preparation
- Recommended Cultivars
- Cultural Practices
- Harvest & Storage
- White Asparagus
- White Asparagus
- What is White Asparagus and How is it Grown?
- Where is it Popular?
- How to Buy it
- How to Cook it and Eat it
Can You Grow Asparagus from Seed?
Starting asparagus from seed is easy, and it’ll save you a lot of money compared to buying pricey asparagus crowns. Nurseries sell asparagus crowns, which are just bare root 1-year-old plants, for as much as $5 each. A potted asparagus plant will set you back $10 to $12 in the spring. A single seed packet, on the other hand, costs about $3 for a pack of 50 to 100 seeds. That’s a tiny investment for a whole field of homegrown asparagus.
Yes! Asparagus is a flowering plant that produces seeds, just like any other garden crop. For many years I believed that Asparagus was a fern, and could only be propagated by division. I had never seen Asparagus “go to seed” because the asparagus crowns purchased from garden centers are all males. The female asparagus plants don’t produce nearly as many edible shoots, and instead, devote their energy to making seed.
Like so many of our food crops, asparagus flowers are bee-pollinated. Male and female plants are separate, and a bee must first visit a male asparagus flower on a male plant followed by a female flower on a female plant.
Since asparagus crowns are generally sold as male only, you’ll only ever see the bright red asparagus fruits (seed pods) if you grow asparagus from seed. Or, in my case, get a batch of asparagus crowns that happen to contain several female plants. Something went wrong in the selection process, and roughly 1/3 of the asparagus crowns I ordered were female.
The female plants are usually culled out because they produce far fewer harvestable spears. With 1/3 of my asparagus beds planted with female plants, the harvests are pretty slim each spring. But a ready source of female plants means that I have plenty of asparagus seed to plant each year.
When you grow asparagus from seed, you’ll have a choice. Either keep the female plants or cull them out to make room for more productive male plants. As a home grower, culling out the female plants will result in a better harvest, but then you won’t be able to save asparagus seed. You also won’t get to enjoy the beautiful bright red asparagus fruit in the fall.
Saving Asparagus Seed
The seeds start out as dense clusters of round green seedpods. They’ll take months to ripen to a full dark red color. While at first, it may look like a huge harvest of asparagus seed, don’t count your eggs before their hatched. Many of those green asparagus seed pods will be knocked off by wind or rain, or picked off early by birds, long before they ripen.
In that time, a dense crop of asparagus seed will be reduced to no more than a small handful of ripe asparagus seeds per plant. That handful of asparagus seed pods still yields quite a few plantable seeds. Each asparagus fruit contains several seeds, and a single female asparagus plant can produce hundreds of seeds in a good year, even accounting for losses.
Leaving just one or two female asparagus plants in your patch is often enough to ensure a lifetime supply of seed, provided those female plants survive and thrive. If you don’t cull out the female asparagus plants, they’ll be roughly 1/2 of your total plants. After planting asparagus from seed, allow the plants to mature for a few years until you can identify the female plants. At that point, I’d suggest culling down to half a dozen female plants at most.
To save asparagus seeds, harvest the berries when once they’ve turned bright red in the fall. Here in Vermont (zone 4), that happens in mid to late September. Allow the berries to dry for a week or two, and then carefully break the seed pods open and extract the seeds.
Lay the seeds out to dry for at least another week before storing them to plant the following spring.
Growing Asparagus from Seed
Planting asparagus seeds is a simple process, and it doesn’t matter whether you’ve saved your own seed, or purchased a package of asparagus seed. Start the seeds indoors 10 to 12 weeks before the last expected frost date in your area. In my cold Vermont climate, the last frost happens the first week of June. That means I’ll need to plant asparagus seed in mid to late March. Most locations see spring a good bit earlier than we do here, and asparagus seeds can be started sometime in February.
Plant asparagus seeds about 1/2 an inch deep in fertile potting soil. The seeds need soil temperatures between 70 and 85 degrees F for good germination, so it’s a good idea to invest in a seedling heat mat. Since most garden crops only need to be started 6 to 8 weeks early, you can reuse the heat mat for tomatoes and peppers later on once the asparagus has germinated.
In the best of conditions, Asparagus takes between 2 and 4 weeks to germinate. Some seeds can take as much as 8 weeks to germinate. That’s one reason why the seeds need to be started so early in the spring. Pre-soaking the seeds in lukewarm water for a few hours before planting can help speed germination, but it’s not strictly necessary.
Transplanting Asparagus Seedlings
Unlike asparagus crowns, which have a large root mass, asparagus seedlings are just getting established. Take extra care in handling them, and avoid damaging their roots. Plant them a bit denser than you would crown to allow for some dieback.
Transplant asparagus seedlings to the garden after the risk of last frost has passed in your area. That’s the same time you set out tomato plants. Crowns are planted 18 to 24 inches apart, but try spacing seedlings about 6 inches apart in rows 18 inches apart. If all the plants thrive, the extra crowns can be thinned out or transplanted later.
How Long Until Harvest?
When you plant asparagus from seed, you’re one year behind schedule compared with planting asparagus crowns. Crown planted asparagus can be harvested in carefully in the 2nd year and fully in the third year. For seed planted asparagus, harvest just a few spears in the third year and then you’ll be able to harvest a full crop in the 4th year.
In the meantime, just carefully tend the asparagus spears, keeping the beds free of weeds. In a few years, they’ll fill out the beds and give you a good crop in the spring as well as showy foliage in the fall.
Asparagus is one of my favorite vegetables. Freshly cut, nothing compares to its crunchy sweetness. Whether steamed, grilled, baked in frittata, or blended into creamy soup, asparagus is a true harbinger of spring. Packed with nutritional value, asparagus is one of the oldest cultivated vegetables.
While some maintain it grows best in colder climates, I find its Mediterranean coastal history makes it a successful North Carolina crop. Prized by early Greeks and Romans, asparagus arrive in the New World with European settlers; and its diuretic properties earned it a place in medicinal gardens. In addition to hybrid varieties, I grow French Heirloom asparagus. Unlike most heirloom plants, there is no discernible flavor difference among asparagus types.
Growing asparagus requires a leap of faith because, even 3-year-old plants should not be harvested the first year they are cultivated. Fern-like fronds grow from spears, and the plants need every ounce of nutrition generated from this growth in order to produce the following year. Although early spears may be a temptation, patient gardeners who properly care for asparagus will be rewarded with many years of production.
Also, carefully prepared asparagus beds are necessary for optimum yield; raised rows of soil, two to four feet apart, should be formed prior to planting. Asparagus plants dry quickly and should never be overexposed to sun or air. Furthermore, the white, leggy roots of asparagus crowns must be carefully splayed across a ridge of soil, with each crown in the center of the raised rows. Space plants about 12 to 18 inches apart and cover with five to six inches of soil.
Once established, asparagus is one of the easiest crops to grow organically. Asparagus beetles, the primary insect threat, may be removed by hand. Aside from potassium, its nutritional needs are few. Weeding is a time-consuming, meticulous task, so and I use a special tool to loosen weeds that threaten asparagus crowns and roots. Fall mulching helps control weeds.
Mature asparagus plants, at least four years old, may be harvested for up to eight weeks. If spears decrease in size to a pencil’s diameter, plants are stressed and harvesting should cease. Even if spears are robust and healthy, asparagus should only be harvested for eight weeks. Fronds will often grow to five feet tall and feed plants during summer and fall. Remove fronds when they become brown and brittle, usually in late winter.
asparagus image by BVDC from Fotolia.com
How to Plant Asparagus in the Fall
Many gardening writers will tell you that the best time to plant asparagus is in the spring. Most of them live in the Midwest or the North. Asparagus planted in the spring in a Southern garden will generally not survive the hot summer. Autumn is the only time of year to plant asparagus in the South.
Clean up the planting site. Remove all weeds, rocks, old roots and other debris.
Add a 3-inch layer of compost to the planting bed and, using the gardening fork, mix it in to a depth of 12 inches.
Add two pounds of 10-20-10 fertilizer and mix it in with the amended soil. According to Master Gardeners at Iowa State University’s Extension office, you will need 2 pounds for every 20-foot row of asparagus.
Dig a trench that is 4 inches wide and 12 inches deep. Place the asparagus crowns in the trench, spacing them 2 feet apart. Cover with 2 inches of soil.
Add another 2 inches of soil as soon as the asparagus plant sprouts to the surface. Repeat this every time the asparagus appears above the soil until the trench is filled in.
Water the asparagus plan when the top inch of soil is dry, allowing the water to drip slowly and deeply into the soil. Depending upon the weather, you may need to water twice a week.
Allow the asparagus plant to go to fern the first year. It’s tempting to pick the spears at this stage, but it’s best to harvest after the second year. Do not cut the tops of the ferns back in the winter.
How Long Can Asparagus Crowns Be Stored?
asparagus image by DuÅ¡an Zidar from Fotolia.com
Asparagus is a perennial vegetable plant, grown from rhizomes that form peaks or “crowns.” For best results, plant asparagus crowns as soon as possible in the spring. However, they may be stored for up to one month at 40 degrees with 80 to 90 percent humidity.
Do Asparagus Plants Need to Be Covered From Cold Weather?
asparagus spear image by hazel proudlove from Fotolia.com
Although a cold-hardy vegetable plant, asparagus spears can be damaged when exposed to temperatures below 33 degrees F. Cover them with a thick cardboard box to protect them overnight from frost. Damaged spears will rot and new spears take four to five days to replace them, according to Iowa State University horticulturists.
How Many Asparagus Can Be Planted Per Square Foot?
asparagus spear image by hazel proudlove from Fotolia.com
Traditional row spacing for asparagus crowns is 9 to 12 inches apart in a 12- to 18-inch-wide trench. In a square foot garden, each 12-inch square can hold two asparagus crowns. Placing each crown 1 1/2 inches from a square’s edge will separate them by 9 inches.
When to Plant Asparagus in Florida
Most gardeners plant asparagus in the form of 1-year-old “crowns” rather than growing from seed. Crowns can be purchased at nurseries, and should be planted as quickly as possible to keep them from drying out.
Spring is the time to plant asparagus. Florida gardeners do not have to wait for the ground to thaw, as northern growers do, so you can plant asparagus in early March in many areas. As long as the soil is warm (50 degrees is about right) and dry enough to work with, it is safe to plant asparagus.
Florida doesn’t really have the right climate for asparagus. This plant is a perennial, and needs a cold dormancy period every winter to stimulate new growth. Because Florida does not have a cold enough season, asparagus produces spears throughout the year, but they tend to be small and spindly. You may be able to get a better crop in north Florida, but cultivating asparagus in south Florida can be a futile endeavor.
How Many Asparagus Grow on a Single Plant?
asparagus image by cherie from Fotolia.com
A single asparagus plant can be harvested when it has eight 8-inch spears on it. The spears should never be allowed to reach more than 9 inches in height. After harvesting, asparagus should be stored in a cool, shaded area and sprinkled frequently with water.
Asparagus spears are a delicious early spring vegetable.
Barbara H. Smith, ©2017 HGIC, Clemson Extension
Asparagus (Asparagus officinalis) is a hardy perennial that is native to the Mediterranean. Once the plants are established, they will provide delicious spears every spring. Although asparagus takes two to three years to begin production, it will be highly productive for seven to eight years before gradually declining.
Choose a site for a permanent asparagus bed that has good drainage and full sun. Plan accordingly as the tall ferns of asparagus may shade other plants. Bed preparation is best done in the fall. Enrich the soil with additions of compost or leaf mold at the rate of 20% by volume.
Follow the results of a soil test to maintain a soil pH between 6.0 and 6.5 and optimal fertility levels. If lime is recommended from soil test results, it should be applied during bed preparation at least three months before planting. For more information, see HGIC 1652, Soil Testing.
In heavy soils, double-digging is recommended. To double-dig, remove the top foot of soil from the planting area. With a spading fork or spade, break up the subsoil by pushing the tool into the next 10 to 12 inches of soil and rocking it back and forth. Do this every 6 inches. Double-digging is ideal for preparing a 6 to 8 inch deep trench required for planting asparagus. The extra work of breaking up the subsoil will greatly improve root growth. The trench is dug 12 to 18 inches wide, with 4 to 5 feet between trenches. Mix the topsoil that has been removed with organic matter and spread about 2 inches of the mixture in the bottom of the trench or bed at the rate of 20% by volume.
The asparagus is a perennial crop, so place the row(s) along a side of the garden space. Dig the trench 12 to 18 inches wide for the asparagus planting.
Joey Williamson, ©2016 HGIC, Clemson Extension.
Purchase 2 year-old crowns, which are larger and will produce more harvestable spears in the next 2 years.
Joey Williamson, ©2016 HGIC, Clemson Extension
Start asparagus from 1 to 2-year-old disease-free crowns. Refer to the table below for the correct planting date for the different gardening regions within South Carolina. If the crowns are planted too late in the spring, they may begin sprouting before planting, which can injure the developing buds.
Planting Dates for Crowns
|Piedmont||Early February – Late March|
|Central||Late January – Early March|
|Coastal||Early January – Late February|
South Carolina Gardening Regions
Set the crowns 15 to 18 inches apart and 6 to 8 inches deep. Mound the soil slightly under each, so that the crown is slightly above the roots. Crowns should be dirty wheat-brown in color, plump, healthy-looking, and have 15 to 20 storage roots. Remove any rotted or damaged roots before planting. Spread the roots out over the mound of soil and cover the crown with 2 inches of soil. As the plants grow, continue to pull soil over the crowns (about 2 inches every two to three weeks) until the trench is filled, and the crowns are 6 to 8 inches deep. Water if rainfall is inadequate.
After the trench is dug and the soil is piled beside the trench down the row, amend the soil with compost and the recommended nutrients. Mix in the amendments well and pull some of this soil into the trench. Mound the soil within the trench to form a ridge down the row (as in the photo above). Place the asparagus crowns over this ridge, spread out their roots, and covered them with 2 inches of soil.
Joey Williamson, © 2016 HGIC, Clemson Extension
The bed above has been planted with asparagus crowns, covered with 2 inches of soil, and the cultivars labeled. Additional soil is still available beside the row to add more around the emerging spears.
Joey Williamson, ©2016 HGIC, Clemson Extension
Asparagus is dioecious which means that the male and female flowers form on separate plants. The female plants expend more energy to produce seeds; therefore, the female plants will have a much lower yield than the males. Old standard cultivars, such as Martha Washington, Mary Washington, and Waltham Washington have a higher percentage of female plants that in turn will reduce yield. All-male hybrid cultivars are now available that will outperform the old cultivars 3 to 1 in production. Typically, the all-male cultivars have around 93% male plants with 7% female plants. After the female plants produce seed, they can be eliminated from the asparagus planting.
Some of the better producing male cultivars are:
- Jersey King—This is vigorous and disease-resistant cultivar with a lower yield than other Jersey cultivars, but will have larger spears. It performs well in warm, southern climates.
- Jersey Knight—A later maturing variety, but this cultivar has the highest quality of spears in the Jersey series. It has a higher yield and performs well in clay soils.
- Jersey Gem—It is an early producing cultivar with medium to larger diameter spears and grows best in cooler climates.
- Jersey Giant—An asparagus cultivar that has a moderate yield with extra large spears, but adapts well to the south.
- Jersey Supreme—This early season cultivar produces high yields. It adapts well to both warm and cold climates.
- Purple Passion—This cultivar has purple spears, but the spears turn green with cooking. Crowns may be 50/50 male and female plants.
Nitrogen, phosphorus, and potassium are all important at planting and throughout the entire life-span of asparagus.
Pre-plant applications of phosphorus and potassium depend on soil test results. It is best to get the phosphorus down into the planting furrow at transplanting because the crowns will ultimately be 6 to 8 inches deep and phosphorus moves very slowly down through the soil. In the absence of a soil test, apply 5 lbs 5-10-10 per 100 feet of row in the trench and cover with at least 2 inches. Then set the crowns over the ridge in the trench.
A complete fertilizer is required in the years following transplanting. A soil test is always the best method of determining the fertilization needs of the crop. In the absence of a soil test, apply 5 lbs of 5-10-10 per 100 feet of row in the very early spring before spears emerge. Then sidedress with 1½ lbs calcium nitrate (15.5-0-0) per 100 feet of row after harvest. For this and most other fertilizers, a pint is equal to a pound. Asparagus also benefits from yearly top-dressing of compost, again at the rate of 20% by volume.
Adequate soil moisture is important to keep young plants growing rapidly. Good growth in the first year is important for large crowns. During the period of stand establishment, they should not be water-stressed or over-watered. Water sufficiently to moisten the soil to a depth of at least 6 inches. Light watering will lead to shallow rooted plants.
To avoid accidentally breaking off spears, weed the bed each spring before the first shoots come up. During the production period, it is best to pull rather than hoe weeds. Maintain a 2- to 3-inch layer of mulch throughout the year.
Harvest & Storage
Depending on the variety, asparagus crowns may need two to three full growing seasons before limited harvesting can be done in the third or fourth year. Less vigorous varieties, such as Purple Passion, may need an additional year to mature. The fleshy root system needs to develop and store food reserves to produce growth during subsequent seasons. In all asparagus planting, cut the foliage down to 2-inch stubs in late winter after they turn brown, but before the spears emerge in spring. Letting the ferns turn brown allows nutrients to be exported from the foliage into the crowns for next year’s growth. A light mulch will help keep the soil surface from becoming too hard for the shoots to break through easily.
Harvest lightly in the third or fourth year for three to four weeks as long as the ferns the year before were very vigorous, bushy, and shoulder-high. Harvest spears daily during the harvest period. Spears that are 6- to 8-inches are the best size for harvest and should be cut or snapped off at the soil surface before the tips begin to separate. Cutting too deeply can injure the crown buds that produce the next spears. If the asparagus is allowed to get much taller, the base of the spear may be tough and will have to be cut.
Stop harvesting when the diameter of the spears has been reduced to pencil-size and allow the spear to grow to full height. After harvest, process or refrigerate immediately. Asparagus can be frozen or canned. Asparagus has an attractive, fern-like foliage that makes a nice garden border.
Asparagus has an attractive fern-like foliage.
Barbara H. Smith, ©2017 HGIC, Clemson Extension
Some gardeners prefer to support the growing foliage with stakes and strings to keep them tidy. In high-wind areas, plant the rows parallel to the prevailing winds so that the plants support each other to some extent.
Plants harvested too heavily too soon often become weak and spindly, and the crowns may never recover. Crown rot or poor production may occur in heavy soil that is inadequately prepared. Water stress during the first two months (while establishing a root system) can reduce yields during the life of the bed.
The primary insect pest is the asparagus beetle. Adults and larvae feed on spears and ferns. Asparagus beetles can be controlled by sprays with carbaryl every 10 to 14 days or with spinosad every 7 to 10 days. These two insecticides have pre-harvest intervals, that is, the time between spraying and harvesting, of 1 and 60 days, respectively. Please see Table 1 for products containing these insecticides.
Diseases that may occur in the home garden include rust, Fusarium crown rot, Fusarium stem canker, stem anthracnose, soft rot, and root rot. To prevent Fusarium crown rot, choose a spot that has never been planted to asparagus. Make sure the soil pH is 6.5 to 7.5. Plant a Fusarium-resistant hybrid, such as Jersey Gem, Jersey Giant, or Jersey Knight. Rust can be controlled with sprays of myclobutanil or sulfur. The preharvest intervals for these two fungicides are 180 and 0 days, respectively. So, the myclobutanil cannot be sprayed until after harvest is complete that year. Anthracnose also can be controlled by myclobutanil, but again, the pre-harvest interval is 180 days. For stem disease control, such as anthracnose or Fusarium stem canker, the affected canes can be cut and removed instead of spraying. Use drip irrigation rather than over-head irrigation to lessen the chance and spread of disease. Please see Table 1 for products containing these fungicides.
Table 1. Insecticides and Fungicides for Asparagus Insect Pest and Disease Control.
|Active Ingredient||Brand Names and Products|
|Carbaryl||Garden Tech Sevin Concentrate (also in RTS1)
Ferti-lome Liquid Carbaryl Garden Spray
|Myclobutanil||Spectracide Immunox Multi-Purpose Fungicide Concentrate (also in RTS1)
Monterey Fungi-Max Multi-Purpose Fungicide
|Spinosad||Southern Ag Conserve Naturalyte Insect Control Concentrate
Bonide Colorado Potato Beetle Beater Concentrate
Bonide Captain Jack’s Dead Bug Brew Concentrate; & RTS1
Ferti-lome Borer, Bagworm & Leafminer Spray Concentrate
Monterey Garden Insect Spray Concentrate
Natural Guard Landscape & Garden Insecticide RTS1
|Sulfur||Hi-Yield Wettable Dusting Sulfur
Safer Brand Garden fungicide Concentrate
Southern Ag Wettable or Dusting Sulfur
Bonide Sulfur Plant Fungicide
Fert-lome Dusting Sulfur
| 1RTS = Ready to Spray (hose-end applicator)
Note: As with all pesticides, read and follow all label instructions and precautions.
For several years in the 1980s, my wife and I lived just north of Germany’s Black Forest, where one culinary highlight in late spring and early summer is white asparagus. More tender, milder, and nuttier in flavor than green asparagus, it quickly became our favorite vegetable, though we’d never particularly liked the green type. In general, white asparagus is preferred over the green type in Europe, though some Americans find it less sweet. White seemed to be the only kind of asparagus grown in southwest Germany, and today, it’s the only kind I grow in southwest Virginia.
Actually, white asparagus is not genetically different from the green kind. It’s simply any asparagus grown in the dark, or blanched. The traditional way to blanch asparagus is to mound mulch or sand around the spears as they emerge. But that technique is a lot of trouble, because it must be done daily, and it makes the spears grubby. All that’s really required to blanch them is to keep them under an opaque cover.
A Simple Blanching Method
I grow my asparagus in a 4-foot-square raised bed, framed by 2 x 12’s of lumber. I use pressure-treated lumber, but if you’re leery of pressure-treated wood in the garden, consider applying a wood preservative to untreated wood or using rot-resistant cedar. The resulting structure looks like a sandbox. During each spring harvest, I cover the entire bed so the spears are in complete darkness, except during the few minutes required to cut spears every couple of days.
I use a simple method to keep the plants in the dark: I cover the raised bed with another box that’s basically a second 4-foot-square frame with a top made of 1/2-inch plywood. The asparagus shoots grow inside this box. I simply set the top on the raised bed, without hinges or other attachments.
Untreated pine is fine for this, because it’s lighter and cheaper and doesn’t rot during its brief period of annual use. (The top stays in the basement the rest of the year.) However, the top is fairly heavy (about 75 pounds) and awkward to maneuver. Many gardeners would need help. I wanted the cover to withstand the strong spring winds here in the Appalachian foothills. An alternative in other regions might be to use 1 x 12’s, then weigh down the top with bricks if necessary.
Even if I were growing green asparagus, I would still use a deep raised bed filled with rich soil to ensure vigorous plants and harvests. In fact, I use the same kind of bed for my strawberries and all my annual vegetables.
How to Build a Covered Raised Bed
Here are some tips for constructing sturdy raised beds out of 2 x 12’s. First, use treated, preserved, or rot-resistant lumber as described above. Untreated wood rots in a few years, and replacing it around a bed like this is awkward. To avoid gaps and soil leakage, make sure your cuts are straight and square. Use three 4-inch deck nails (the ribbed kind used in deck construction) per joint. Smaller or nondeck nails don’t hold as tightly.
If you like, you can trim the top edges of the bed with 2 x 4’s. Attach them wide-side-up to the edges of the raised bed frame. The molding makes it easier to set on the top cover.
When, How, and What to Plant
Early spring is the best time to plant asparagus in most regions, except if you live where winters are mild. In that case, plant in late fall. Start by amending the soil with compost. Asparagus prefers soil that is neutral to slightly acidic, so if necessary, add lime to correct acidity or sulfur to correct alkalinity. The plants come as crowns, which are clumps of roots. Nine crowns, planted 2 to 4 inches deep and about 15 to 16 inches apart, will fill a 4-foot-square bed in about three years. Both male and female plants produce edible spears, though all-male varieties are said to be more productive. (I haven’t noticed much difference.)
‘Mary Washington’ and ‘Jersey Knight’ are good varieties, and plants are readily available from mail-order catalogs. ‘Mary Washington’ may be more rust-resistant. ‘Jersey Giant’ produces such large spears that the largest among them may be a little tough and stringy. Based on experience, I would avoid no-name bargains. They may be inferior strains being unloaded by a breeder.
Care and Harvesting of Asparagus Plants
Each year, when the first spears begin to emerge (around the first of May in my area), I apply a cheap, fast-release lawn fertilizer, such as 30-3-3, and water it in. This encourages good top growth for the harvest period. Then I put on the top. The bed won’t receive rain, of course, while the top is on, but I seldom have to water, because the covered soil doesn’t dry out much.
Surprisingly, air circulation isn’t a problem, either. During my first harvest, I created some openings for ventilation. Not only did this turn out to be unnecessary, but it let in a little indirect light, which made the spears pale green instead of white.
Pests and Diseases
Japanese beetles are the main pests in my garden, so I put out a trap. The other common pest is asparagus beetle. Fortunately, though, in both cases, my harvest is over before the beetles begin theirs, and by that point they cause relatively little damage compared to the size of the plants. I have rarely had to apply a pesticide.
An occasional problem is rust, which shows up in a few wilted spears. A standard vegetable-garden fungicide seems to cure it (but maybe the problem would clear up on its own). After cutting off the infected spears, I drench the soil with the fungicide, trying to avoid getting any directly on the good spears that remain. (To be safe, I wash those spears thoroughly before cooking.)
When and How to Harvest
Be sure to harvest — or at least peek under the top — every two days or so throughout the cutting season. The spears grow fast in the dark, and if you go too long without checking, some will grow too tall and bend after reaching the plywood ceiling.
Many growers say it’s best not to harvest any spears in the first two years. That’s probably true, but raised beds like these are so efficient that it really doesn’t hurt to harvest for two to four weeks the second year. After that, you can harvest for four to six weeks each spring, or until most of the spears start getting too spindly to be worth cutting.
When the harvest is over (early June in western Virginia), I remove the cover. The plants need full sun in summer. I apply a complete fertilizer, such as 10-10-10, immediately after the harvest and again in midsummer.
Plant Care After Harvest
Uncut asparagus spears eventually grow into 6-foot-tall fernlike bushes, with attractive red berries on female plants. An important point: Let the plants grow as big as they want. Don’t cut them back, because top growth is proportional to root growth, and you want maximum root growth if you also want a maximum harvest. Little weeding is needed due to the dense shade provided by the cover.
In all but the hottest climates, plants die back to the ground in the fall. Either way, cut them down then. After that, because the soil level usually sinks a little during the growing season, I top it off in late winter with an inch of fine bark mulch. It’s attractive and eventually decomposes into soil. But because pine bark acidifies soil, I check the soil pH annually and sometimes add some fireplace ashes or lime to bring the pH closer to neutral.
Menu Options for White Asparagus
Several dishes, such as veal Oscar, call for white asparagus. In Germany, cooks make a mouthwatering cream of white asparagus soup. But we usually just steam ours until barely tender, then add butter, salt, and freshly ground black pepper. (Children often prefer asparagus to other vegetables, because it’s one veggie that proper etiquette permits us to eat with our fingers.) We try to save our white asparagus for special meals, though. If you’ve never tried it — and especially if you think don’t like asparagus — you’re in for a treat.
Christopher O. Bird is the author of Modern Vegetable Gardening. He lives and gardens in Riner, Virginia.
What is White Asparagus and How is it Grown?
White asparagus is the same as green asparagus but grown without daylight. Denying the spears daylight as they grow prevents photosynthesis from taking place and this is the process that produces the green colouring in plants.
The plants are grown in the dark by piling soil on top of the spears as they appear and then cutting them well below the surface with a special knife before they grow through the soil into the daylight.
The varieties planted to produce this type of Asparagus are generally different from those planted for green asparagus.
Growing the spears this way involves more labour and inevitably therefore makes the white spears more expensive.
Where is it Popular?
It is very very popular in Europe with the exception of the UK where green asparagus predominates. The Netherlands, Spain, France, Switzerland and especially Germany are all big White Asparagus consumers.
Certain regions of Germanany have very sandy soils that are particularly suited to the growing process and in these areas White Asparagus or Spargel is big business. During the spargel season many restaurants (“Spargelhof”) open up in these asparagus growing regions serving spargel menus, organising “Spargel Routes” and week long festivals take place with music, Spargel queens etc.
On the continent white canned asparagus sits on all the supermarket shelves alongside other canned products. From the volumes for sale it must be very widely eaten.
Whilst green asparagus comes in different stalk thicknesses (stalk thickness is in no way related to quality but relates to variety) the thickest stalked white variety is valued most highly and it is graded as follows:
Extra – stalks >12mm diameter, straight and good quality – expensive!
Handelsklasse I – stalks >10mm diameter, fairly stright although a little bend allowed – good value
Handelsklasse II – stalks >8mm diamter, less stringent shape requirements – economy!
How to Buy it
Around 1/2 of the German crop is sold through roadside stands and farmers markets during the season. The Germans really go to town on eating it when it is fresh. The Netherlands, France and Spain also grow the vegetable in quantities and some of this product is canned whilst the rest is sold fresh. The Spanish are very proud of their crop where it is known as Esparrago. China also grows very large quantities of white asparagus for canning much of which is consumed on their domestic market.
If you want to buy fresh white asparagus in the UK or USA you will need to search it out or buy it imported online. Beware it can be very costly! If you want to try the canned variety you will get thin stalked jars if you look at the top of many supermarket shelves at simliar prices to green canned asparagus. However if you want to try the big jumbo stalked spears you will probably need to buy online and again prices can be steep.
How to Cook it and Eat it
The first thing to say about spargel is that it must be peeled. Once the outer layer is peeled away cook it as for green asparagus. The Germans typically eat fresh spargel with cooked or cured ham and new potatoes and often add a hollandaise sauce.
We have a few canned asparagus recipes and will be bringing you more recipes using this vegetable in due course.
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