- Growth Rate of Oak Trees
- Vigorous Growth
- Moderate to Fast
- Californian Oaks
- Landscape Plants
- Plant Specifications
- Types of Oak trees
- Oak Tree Root System
- Uses of Oak Tree
- What tree where?
- Vulnerable to an epidemic
- Structurally Vulnerable
- Severely Invasive: The Naughty List
- Damaging Roots
- The Right Tree for the Wrong Place
- Minor Human Health Hazard
- Annoyance Factors
- So what should we plant?
Growth Rate of Oak Trees
oak tree with acorn image by Ruslana Stovner from Fotolia.com
The growth rate of oak trees varies greatly depending on the particular species. Oak tree species exist either as deciduous or evergreen trees and exhibit a range of growth from slow to rapid. Identify different species that are attributed to varying rates of speed for the best selection for your home landscape.
For growth rates to reach their ultimate potential, good care of your oak trees is necessary. Oak trees of all species generally thrive in full sun exposure to partial shade, according to the Clemson University Extension. Excessively shaded environments may slow the growth process. Grow oaks in acid, well-drained soil and avoid extremely wet conditions that may increase susceptibility to disease.
The white oak tree species (Quercus alba) is a tall deciduous tree that grows up to 100 feet tall. The growth process is a slow one, with white oaks producing new growth at a rate of 10 to 15 feet within a span of 10 to 12 years, according to the Clemson University Extension. Though growth is slow, white oaks have a life expectancy surpassing 100 years.
Moderate to Fast
The deciduous Southern red oak tree (Q. falcata) has a moderately fast growth rate. This tree reaches a height of 70 to 80 feet and acquires new growth at a rate of 25 feet every 20 years, according to the Clemson University Extension. English oak trees and bur oak trees also have moderate growth rates and both display yellow-brown foliage in autumn, according to the Colorado State University Extension. The Southern live oak (Q. virginiana) has a moderate growth rate; the Southern live oak reaches up to 60 feet in height, according to the University of Florida IFAS Extension.
Water oak trees (Q. nigra) have a rapid growth rate of approximately 25 feet per 10 years, according to the Clemson University Extension. Water oaks reach up to 60 feet in height. Willow oak trees (Q. phellos) reach up to 75 feet in height and are considered rapid growers with new growth of 25 feet every 12 years. Pin oaks (Q. palustris) exhibit a rapid annual growth rate of 18 inches; tree height reaches 70 feet.
Growth rate is affected and inhibited by common problems like pests and disease. For example, problems like scale, an insect infestation of oaks, often results in stunted growth. In mild cases, scale is controllable through hand removal, but when infestations become severe, an application of horticultural oil is necessary, according to the Clemson University Extension. This insect pest, in addition to other potential conditions, decreases the vigor of oak trees; trees in decline suffer health and growth problems and occasionally face death. The moment you notice abnormal symptoms on your oak tree, determine the underlying problem and the appropriate management method.
SERIES 18 | Episode 08
After periods of drought we need to reassess the types of trees we’re planting in our gardens. Californian oaks are one example that will thrive in parts of Australia with a Mediterranean climate and live for hundreds of years.
Oaks are part of the Quercus genus of the family fagaceae. Of the 531 species of oaks, nearly half occur in North and South America. Others are found in Europe, North Africa and North West Mexico – from a wide rainfall, soil and temperature range.
The collection of Californian oaks, at the Waite Arboretum in Adelaide, was planted 50 years ago and has thrived for the past 40 years with no other watering other than around 625 millimetres of annual rainfall. So that means they’re pretty tough.
Some to look out for include a deciduous Californian variety called Quercus douglasii, or the blue oak. What I just love about this tree is its attractive blue green foliage. The leaves are relatively small, but it even has interesting acorns which are rather elongated.
It’s a really tough tree, tolerant to both drought and flooding. It grows where it naturally receives between 500 and 1,000 millimetres of rainfall a year. In its natural state the tree reaches up to 20 metres high, but the specimen we filmed, which is 50 years old, is only about 12 metres high by 10 metres wide. They’re very long lived trees, with the oldest known specimen being 400 years old.
Another beautiful tree is the valley oak, or Quercus lobata. In its natural habitat it’s the largest North American oak, reaching up to 30 metres high. The specimen we filmed is 50 years old and is 12 metres high by 12 metres wide.
What’s interesting about the tree is, that despite being deciduous, it actually comes back into leaf in early August, which means there is only a brief period when the tree is bare. It has medium-sized green lobe leaves, typical of an English oak.
The valley oak is incredibly drought tolerant. It can send its roots down deep into the ground in search of ground water. Amazingly, the roots have been measured up to 26 metres deep.
Another tree with its beautiful canopy that is perfect for creating shade on a hot day is an evergreen oak called Quercus agrifolia, or the live coast oak – a native of Western California and Mexico and perfect for a Mediterranean climate. The foliage is lovely and green, but not exactly oak like. The leaves are quite leathery and they’re actually prickly on the edge, making it almost holly like. The oak is also extremely drought tolerant and very long lived, and this specimen has grown 10 metres high by 11 metres wide in 50 years.
If you’d like to try a Californian oak, there are a few things to keep in mind: Some oaks don’t transplant well and generally they don’t like root disturbance. Acorns can be a hazard on paved surfaces or in street settings. Remember also that although oaks are slow growing, they’ll eventually become large trees so they may not be suitable for small suburban gardens. However, if you’ve got the space and you’ve yearned to leave something of beauty for your grandchildren, then a Californian oak is a great waterwise choice and they’re just lovely looking trees.
The Waite Arboretum
Interesting Information About Plant:
The pin oak is widely used for landscaping around highways and other places that are readily seen by many people. The distinct pyramidal shape, with the green glossy leaves make it an attractive plant. It originates from here in North America and grows well in a wet area and in areas affected by human activity. It requires wet and acidic soil to reach its full potential, and it is a rapidly growing tree if the requirements for the conditions are met. In the best conditions, which are in the south and the Midwest, the Pin Oak can grow to be seventy feet tall and forty feet wide if located in the open.
The medical and edible uses of the plant are limited. The acorns secrete a powder that can be used for a thickening agent is soups and stew and Native Americans would grind the acorns to make coffee.. The pin oak is very common tree to this region of the world, and can be found throughout any area in the United States. The Pin Oak has a few medicinal uses. It has been used for the treatment of hemorrhages, chronic diarrhea, and dysentery. The bark has also been used to treat colds. Pin Oak has also been used as a bug repellant. In modern times the wood has been used for furniture and flooring, on interior trimmings, and as shingles.
Scientific Name: Quercus palustris
Family Name (Scientific and Common): Beech Family, (Fagaceae)
Continent of Origin: North America
Plant Growth Habit: Large Tree
Height at Maturity: More than 10 Feet
Life Span: Perennial
Seasonal Habit: Deciduous Perennial
Growth Habitat: Full Sun
Manner of Culture: Native Species
Thorns on Younger Stem: No
Cross Section of Younger Stem: Roundish
Stem (or Trunk) Diameter: More Than The Diameter of a Coffee-Mug
Produces Brownish Bark: Yes
Bark Peeling in Many Areas: No
Characteristics of Mature (Brownish) Bark: Lines Go Up-Down
Type of Leaf: Flat, Thin Leaf
Length of Leaf (or Leaflet): Between the Length of a Credit Card and a Writing-Pen
Leaf Complexity: Simple
Edge of Leaf: Smooth
Leaf Arrangement: Alternate
Leaf has Petiole: Yes
Patterns of Main-Veins on Leaf (or Leaflet): Pinnate
Leaf Hairiness: No Hairs
Color of Foliage in Summer: Green
Change in Color of Foliage in October: Changes to Dry Brown
Flowering Season: Summer
Type of Flower: Like a Pine Cone
Color of Flower: Brown
Shape of Individual Flower: Bilaterally Symmetrical
Size of Individual Flower: Smaller than a Quarter
Sexuality: Male and Female on Same Plant
Size of Fruit: Smaller than a Quarter
Fruit Fleshiness: Dry
Shape of Fruit: Acorn-like
Color of Fruit at Maturity: Brown or Dry
Fruit Desirable to Birds or Squirrels: Yes
Common Name(s): Pin Oak
Louisville Plants That Are Most Easily Confused With This One: Scarlet Oak, Chestnuts, and Beeches
Unique Morphological Features of Plant: “U” shaped between major lobes of the leaf. Young oaks can retain leaves through the winter though they are dead
Poisonous: None of Plant
Pestiness (weedy, hard to control): No
Page prepared by:
Jason Ford & Ryan Sanders
- Broadleaf, deciduous tree, 60-75 ft (18-23 m), prominent central stem, pyramidal, descending lower branches. Leaves alternate, simple, 7.5-15 cm long, 5-7 lobes, wide deep sinuses (“U” shaped in comparison with “C”-shaped sinuses of Q. coccinea), tips slightly lobed and bristle-like, glossy dark green; in fall foliage ranges from russet, bronze to brilliant red. Blade tends to be “V”-shaped at attachment with petiole. Many leaves hang on all winter. Fruit (acorn) is small, about 1.5 cm long, the nut is enclosed only at the base by a thin, saucer-like cup; two seasons to mature.
- Sun. It has a shallow root system so more easily transplanted than many other oaks. Shows iron chlorosis (yellow foliage) on alkaline soils, therefore it should only be planted on soils that are at least slightly acid. It will tolerate wet soils (one of the swamp oaks), but is best in rich, acid, well-drained soil. One of the fastest growing oak (as much as 15 ft (4.5 m) in 5-7 years).
- Hardy to USDA Zone 4 Native range from Massachusetts to Delaware, west to Wisconsin and Arkansas.
- palustris: of swamps
- Oregon State Univ. campus: on Washington Way on the north edge of the football practice field, along railroad tracks.
Q: I am considering planting pin oaks on my property for their large size and fast growth. In pictures, the tree has a very neat and formal shape, which I also like. Their nuts are small, which I think would be good for wildlife. What do you say? – Trisha D., Oneonta, AL
A: Pin oak, Quercus palustris , does indeed grow large and quite fast. Along with the closely-related water and willow oaks, Q.nigra and Q. phellos , respectively, it is arguably the fastest-growing oak species. I won’t say it would out-pace a willow, Salix spp. or tulip poplar, Liriodendron tulipifera , but its branching structure is more sturdy and the wood stronger, resulting in a typically longer lifespan. One of the cardinal rules of trees is that with fast growth you get weak wood. This is not always 100% true, and the pin oak is a case in point. In my mind, this handsome species is one of the finer oaks – among many others – but no tree is perfect and you should read the caveats below before deciding if this one works for you.
Pin oak is a large deciduous tree whose form, or growth habit, changes over time. In its youth and into middle-age, the shape is indeed very regular, a dense pyramid with many straight branches from the trunk, usually much taller than broad. Most distinctive is that the upper branches ascend, the middle branches are horizontal and the lower branches point downward (see image). Often, the lowest branches will remain on the tree even after they have atrophied. Most other species shed these branches as a normal part of their growth and development. Pin oaks are not rapid “self-pruners.” At full maturity, pin oaks have an upright oval form, with many fine inner branches, the lowest ones always pointing (drooping) downward.
This was one of the first trees I learned to identify; once that branching pattern was set in my mind’s eye, pin oak stood out from everything else, even at highway speeds. Also characteristic is pin oak’s tendency to retain a significant amount of (dried, brown) leaves on the lower and inner branches through the dormant season. Other oaks and beeches, Fagus spp. do this as well, but this juvenile trait slowly dissipates with age. I have read that the spent leaves offer a degree of winter shading, protecting the thin bark of young trees from potentially scalding sun, but I’m not sure this is well-researched. The fruits, technically acorns and not nuts, are smaller than one-half and inch and, like all oaks, are relished by many types of wildlife, including birds such as blue jays and turkeys.
The dense growth, drooping lower branches – which, on unpruned specimens can almost sweep the ground – and winter leaf retention make pin oak somewhat better than other deciduous trees for screening purposes. However, those low branches can make the species less suitable as a general shade tree because they make it more difficult to get “headroom” beneath it. Repeated pruning of lower branches, called limbing up or canopy elevation, as the tree matures can mitigate this, but the lowest branches on the tree will always tend to droop a bit. For this reason, I probably would not advise planting it in a location where the branching would be a liability (such as next to a patio, driveway or parking area). Several selections have been made for somewhat more upright branching, ‘Sovereign’ and ‘Crownright’ (‘Crown Right’) are two. These are hard to locate in the trade and the differences, on mature trees, are not significant. In addition, the trees are propagated by grafting (oaks are notoriously difficult/impossible to propagate from cuttings) and graft incompatibilities have been reported, sometimes a number of years after “successful” planting. Ill health, decline and death typically follow.
Generally, pin oak grows best in moist, bottomland soils whether sandy, clayey or rocky. After establishment, pin oak shows excellent drought tolerance, so I would not limit its use to only moist soils. Pin oaks have good fibrous root systems, which makes them available in larger sizes with the roots balled and burlapped. I usually rave about the benefits of fall and winter planting for woody plants, but I would only transplant pin oaks in late winter or early spring. One soil factor cannot be “negotiated” and that is high pH – pin oak does not tolerate a pH over 6.5 (according to Ohio State University, 5.0-6.5 is the optimal range) – so I strongly advise you to get your soil tested. If the pH is higher than 6.5 you need to forget pin oak and start looking at other potential tree species. In circumneutral and alkaline soils, pin oak develops severe chlorosis which manifests as yellow leaves with green(er) veins. Chlorosis eventually proves fatal and acidifying soil is difficult (and does not last) especially when you consider the trying to alter the substantial soil volume occupied by the roots of a large tree. So test, test, test!
Pin oak is limitedly native in Alabama but very common in the mid-Atlantic and northeast (both as a native tree and a landscape subject). My three “go-to” range map sources differ somewhat as to precise location (one shows no nativity at all), but show a few populations in the northern Ridge & Valley and Piedmont provinces. My next point is worth careful consideration: like many native trees, the adaptability of pin oak shows strong regional tendencies. We use the term provenance to refer to the origin of seeds that plants are grown from. No maps I looked at show native pin oaks in your county; this doesn’t mean they do not exist, just that no one has documented them. Still, I would consider your area as marginal since it is at/beyond the fringe of pin oak’s native range. For this reason, your best chances of success would be with pin oaks grown from seed from a population as close as possible to where you live. It is often not possible to determine the seed source of nursery-grown plant material. So talk to your suppliers to see if they can provide this information.
If your heart is set on planting and enjoying a pin oak, and if you have the right location, and if your pH is below 6.5, and if you wait to plant in late winter or early spring, and you can be relatively assured of a fairly local seed source (I would settle for southern Tennessee or northern Georgia, as well as Alabama), then you will have a beautiful and carefree tree for many years to come. This sounds like a lot of “ifs” but this is one tree that cannot live just anywhere.
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An Oak is a tree or shrub belonging to the Beech family. Oaks have genus Quercus which covers about 600 species all over the world. Oak trees are characteristics of Northern Hemisphere. Oak trees are available in Temperate forests, Tropical forests and Mediterranean forests. They are great shade trees and many species of Oak have scenic fall colours. Fruits of Oak trees are called as Acron. Acron is technically a fruit that contains seeds but due to its hard outer layer, it is regarded as a nut. Acron is specific to the trees of Quercus Genus including Oaks.
Oak trees are a vital part of a forest ecosystem. The bark of many Oak trees is thick which protects them from forests fires. The trunk of Oak trees stores water for use during unfavourable conditions. Oak trees support a complex ecosystem with many species including humans. Oaks are susceptible to fungal diseases which rot the inner part of the plant. Oak trees are common in America, Asia, Europe, and North Africa. Mexico (North America) is the largest centre for Oak trees containing 160 species overall, following China (Asia) which holds approximately 100 species.
The Oak tree is officially the National tree of the United States of America (USA). Oak is one of the most loved trees in the world and is considered as a symbol of strength, morale, resistance and knowledge. In Greek mythology, Oak was a symbol of Zeus (The God of Thunder).
Index of Article (Click to Jump)
- Oak trees are very large in size. The average height of an Oak tree is 70 feet having a width of 9 feet. The branches of Oak trees can reach up to 135 feet in length.
- Due to their large size, Oak trees can absorb a great amount of water. An average Oak tree can absorb nearly 50 Gallons of water per day.
- Most Oak trees have lobed leaves but it can be serrated and flat in some species. Leaves are spirally arranged.
- Oak trees produce acrons from the age of 20 to 50 years. Each acron takes 6 to 18 months to mature. Young acrons contain Tannic acid which is toxic for cattle and can cause stomach ulcers and kidney failure. Tannic acids in the acron protect the Oak trees from fungi and insects.
- Oak trees are deciduous but few are evergreen, for example, Live Oak trees.
- The average life span of Oak trees is 200 years while some species survive up to a thousand years.
- Oaks produces both male (androecium) and female part (gynoecium) of the flower, also known as Bisexual or perfect flowers.
Types of Oak trees
There are 30 different types of Oak trees found all over the world. Overall, the 600 species of Oaks are categorised into two main types, that is, Red Oak trees and White Oak trees.
|Red Oak Tree||White Oak Tree|
- Leaf of Red Oak Tree
- Leaf of White Oak Tree
Live Oak Tree
- The Live Oak trees, also known as Evergreen Oak trees are the group of Oaks that do not shed their leaves throughout the year, that is, always remain alive. Live Oak trees keep their leaves until they die.
- As depicted by the name, these Oaks remain evergreen/live even when other Oak trees become leafless during the winter season.
- This evergreen foliage of Quercus Genus is common in North America, especially in the warmer area along the Atlantic coast from southeast Virginia to Florida, west along the Gulf Coast to Louisiana and Mexico, and across the southwest to California. They’re also present in Southern Europe and South Asia.
Pin Oak Tree
- Pin Oak, scientific name: Quercus palustris, is an Oak of Red Oak tree category. It is a popular landscape Oak due to its easy transplant and pollution tolerance. Pin oak is also commonly called swamp Spanish oak due to its tolerance to wet soil.
- Pin Oak trees can be easily distinguished due to the oval shape of their canopy.
- They’re fast growers and prefer clayey soil and bright sun. It prefers a minimum of 6 hours of daily unfiltered sunlight for a better outcome.
- Pin Oak trees are mainly found in eastern and central America. Other than America, they’re also native to the extreme south of Ontario, Canada and are even introduced in Australia, South Africa and Argentina where they’ve well adapted to the climate.
- Pin Oaks have glossy dark green leaves and the plant can reach up to a height of 60 to 70 feet.
- Pin Oak tree’s leaves turn scarlet and bronze during fall.
Water Oak Tree
- Water Oak Tree, scientific name: Quercus nigra, is also a plant of Red Oak family. It is native to North America and plays a great role in maintaining the ecosystem of New Jersey to Florida and west to Texas.
- This plant is short-lived compared to other Oak trees and is easy to nurture. The average life span of Water Oak tree is 30 to 50 years.
- The wood of Water Oak is comparatively soft. It is a weak wooded tree prone to many diseases. It is medium-sized, shade and ornamental landscape Oak tree.
- Water Oaks can tolerate the extreme quality of the soil. It prefers to thrive in wet and swampy areas but can also grow in drained, compacted soil.
- Water Oak tree is a copious producer of acrons due to which it is a part of food chains of a variety of nut loving animals including squirrels, raccoons, turkeys, pigs, ducks, quail and deer.
Oak Tree Root System
The roots of the oak trees are very strong and extend to a great distance underground compared to the tree canopy. Initially, when the roots arise from the acron, they grow as a Taproot system with primary root growing horizontally deep into the soil but later on, with the plant maturation, the Taproots gets transformed into an extensive root system.
Roots of the Oak trees spread up to 3 to 7 times the diameter of the tree’s crown, therefore they need a wide space, not just above the ground but under the ground as well to thrive to their fullest. They lie around 18 inches from the ground. Root hair present on the tip of the lateral roots helps in the absorption of water and nutrients from the soil which gets transported into the system. Oak tree roots require obstacle-free space under the ground with no underground pipeline, buildings or the roots of other large trees. If two Oak trees of same species are grown side by side, they can share a common root system by the process of grafting.
Roots of Oak trees grow best in the soil which is little acidic having a good amount of oxygen. The amount of water in the soil depends upon species to species. Some roots grow best in wet soil while some prefer drained, compact soil. Few species of Oak trees even survive in drought conditions, for example, native California oaks (e.g California white oak).
Roots of the Oak tree shows the symbiotic relationship between fungi named Mycorrhiza. A symbiotic relationship is a unique type of interaction between organisms of two different species which can be either harmful or beneficial to those species. In the case of Oak roots and Mycorrhiza, the fungi form a layer over the roots and protect the roots from other disease-causing fungi. Mycorrhiza also increases drought resistance capacity of the Oak trees and shares the nutrients they collect with the roots.
Oak Tree Root Diseases
Roots of Oak trees are susceptible to fungal diseases. Due to the fungal attack on some roots, the roots get rotten and the infection reaches up to the tree trunk. Due to the fungal infections, the tree gets cut off of the water and nutrients supply and die eventually. Fungus feeds on the roots of the Oak trees. Various anti-fungal sprays are available to keep the Oak trees from getting the infection.
Uses of Oak Tree
- Natives of North America used Red Oak for treating ailments and wounds. Oak tree can also be used to treat Diarrhoea, asthma and can be used as an antiseptic.
- The bark of the Oak tree contains tannin and this tannin is used for making tannin leather from hundreds of years.
- One of the most important uses of the Oak tree is for shade. Due to their large crown size, they’ve been used as shade providers especially during summer seasons.
- Oak trees hold great importance in an ecosystem as they are food providers and habitat for various animals and bird species.
- White Oak wood is popular in timber trade as its wood is highly durable and is used for furniture, flooring and making cabinets in the houses.
Something simple and extremely fundamental must underpin any effort to increase the biodiversity of the urban canopy: adequate quantity and quality soil and water. That’s it. If a guy wanted to grow a great tree in a typical 4 x 4 urban tree opening, he could add macronutrients (NPK), micronutrients (Mn, Mg, etc.), compost tea, mulch, foliar sprays, even have the tree’s nails done – none of that will matter. That tree is headed for an early death. That’s how unimportant all those other things are compared to adequate quantity of soil, adequate quality soil, and water.
Once good growing conditions are established, then tree selection becomes extremely important. We’ve come to over-rely on a very small selection of trees in our cities. Today I’m going to go through a list of all the trees not to plant (I’ll go over trees that we should plant in a future post).
What tree where?
Probably 5 percent of all tree species can grow just about anywhere. We know them well, and while we’re comfortable with these species, this is exactly what we should stop planting.
Why? There are a few genera that are vastly overrepresented in the North American urban forest. These trees are vulnerable to four catastrophic failures that are all human health and safety factors:
- an epidemic;
- a fall tree/branch hazard to people, cars and buildings;
- invasive species that destroy wild & natural areas;
- roots that enter sewer pipes and other underground utilities.
The lists that follow are not comprehensive, the idea is to eliminate from consideration the 5 to 10 percent of trees that cause severe problems and don’t belong in urban areas. I’m telling you which city trees not to plant because I think it’s easier for people to stop doing an existing thing, rather than start doing a new thing. On to the lists.
Vulnerable to an epidemic
(Insect, Virus, Bacteria, Fungi)
- Ash (Fraxinus): vulnerable to Emerald Ash Borer (EAB); except Manchurian (mandshurica)
- Cherries (Prunus): vulnerable to many insects and diseases; most species & cultivars
- Colorado Blue Spruce (Picea pungens): Cytospora Canker eventually will kill all needles leading to defoliation and death
- Crabapples (Malus): vulnerable to Cedar Apple Rust and Fire Blight which completely defoliates trees; Most species & cultivars
- EAST Section Lobatae: Black Oak (Q. velutina); Water Oak (Q. nigra); Northern Red Oak (Q. rubra/borealis); Pin Oak (Q. palustris); Northern Pin Oak (Q. ellipsodalis); Willow Oak (Q. phellos),
- Elms (Ulmus): vulnerable to Dutch Elm Disease (DED); except DED resistant ‘Accolade’; ‘Homestead’; Lacebark or Chinese (U. chinensis ‘Allee’); Cedar Elm (U. crassifolia)
- Leyland Cypress (Cupressus leylandii): Canker Disease, West of the Rockies
- Lombardy Poplars (Populus nigra’Italica’): vulnerable to Fungal Leaf Spot
- Maples (Acer): vulnerable to Asian Long Horned Beetle, especially NOT these Eurasian species: Hedge (A. campestre); Norway (A. platanoides); Amur (A. ginnala); Tatar (A. tatarica); 3 North American Natives that are seriously overplanted and are thus extremely vulnerable to an overseas epidemic: Silver (A. saccharinum); Red (A. rubra); Sugar (A. saccharum)
- Pines (Pinus): especially Austrian (P. nigra); Ponderosa (P. ponderosa): Dothistroma Needle Blight eventually will kill all but current year’s needles leading to defoliation and often death
- Planetree (Platanus): Anthracnose; except 2 London Plane tree cultivars (P. x acerifolia ‘Bloodgood’ & ‘Columbia’)
- Red Oaks (Quercus…Section Lobatae Eastern North America; Section Protoblanus of Western North America): the Red Oak group (with bristles on their leaves); have an extreme susceptibility to Oak Wilt. Additionally the Red Oak group has a huge number of species and is found on 4 of the 5 continents that grow trees, this increases the odds of an epidemic dramatically.
- WEST Section Protoblanus: e.g. Canyon Live Oak (Q. chrysolepis)
- White Birches (Betula): vulnerable to Bronze Birch Borer; most species and cultivars, except River (nigra and nigra ‘Heritage’)
A note on maples
I’m afraid that the coming story for maples is not a happy one. I believe an epidemic similar to Dutch Elm Disease, Emerald Ash Borer, or Chestnut Blight awaits them. In U.S. cities east of the Mississippi River, Maples now make up over 30 percent of the urban forest canopy – tens of millions of trees. Perhaps it will be Asian Long Horned Beetle, which is already in some states in the United States; perhaps it will be something else we don’t even know about yet. It is a matter of when, not if, and it’s safe to say the devastation will be significant. So, I appeal to all responsible professionals in the business of planting trees to please stop planting maples.
(soft or weak wood; included branch attachments; unstable root plates)
Severely Invasive: The Naughty List
(Self-seeds and overruns native trees, shrubs, grasses and forbs in wild and natural areas, think Kudzu Vine)
Depending on your point of view, trees on this list ascended or descended onto the list because in over 200 United States counties they are listed as invasive, according to the 2014 USDA’s Invasive Species Group. This list is comprehensive for these purposes. But this list does not include aggressive natives growing outside their pre-European Contact range such as Black Locust, Hedge Apple, Eastern Red Cedar, etc. or commercial fruit and nut trees that may have escaped from cultivation and become problematic.
The trees below have very vigorous root systems, they are phriatiphytes growing where constant supplies of water are available: along streams and lakes. These trees roots, in their search for water and nutrients, occasion on waste water pipes (sewer pipes). Because this water and nutrients supply is perpetual, these trees’ roots will intrude and fill these pipes with roots, eventually coming to rely on this artificial source, and completely obstructing them. This does not seem to be a problem with stormwater pipes.
The Right Tree for the Wrong Place
There are also a number of tree species that can cause problems in some places and contexts while being great choices for others. Consider the species on these lists based on the factors present on your site.
Minor Human Health Hazard
(massive cones that can hurt people, asthmatic inducing levels of pollen)
These are trees that can be planted in the city and will have no serious issues with pests, invasiveness, invading roots, structural problems, or people getting hit hard on the head. Almost all of these problems can be solved using a broom. Except for their perceived messiness, these are very, very sound trees, and some of them will show up on our recommended planting list.
(large pods, fruits, nuts or abundant airborne seeds)
- Chinese Chestnut (Castinea mollissma): Husk of Nuts
- Gingko’s Females (Ginkgo biloba Female): Fruits; Use males only
Fruit and Sap
- American Linden (Tilia americana): Sap on Cars]
- Asian Mulberry (Morus alba): Pavement Staining Fruit
- Ginkgo Females (Ginkgo biloba Female): Slippery Fruits
- Sweet Gum (Liquidamber strycaflua): Gum Pods
So what should we plant?
Credit for these lists goes also to the following from their writings and conversations: Dirr, Coder, Urban, Johnson, McPherson, Gilman, Harris, Shigo. The next and final article in this series will list the trees that are proven contenders over the years in cities. This is a large selection that will grow well in cities given reasonable care (adequate soil quality, adequate soil quantity, and water); use the list widely with no genus exceeding 5 percent of the city’s Urban Tree Canopy.
Go forth and prosper, young trees.
This is part three in a series about species diversity in the urban forest. Read parts one and two.
L. Peter MacDonagh is the head of Science + Design for The Kestrel Design Group.
Alexxx Malev / CC BY-SA 2.0