Why do we need tough trees? What challenges do we face in the urban canopy toady that requires specific planning for canopy diversity? Trees are our best choice for the fight against air pollution, poor air quality, heat islands, and climate manipulation. When we have trees in our landscapes, parks, and streetways, our overall health, mood, and well-being is better, even if we do not realize it.
Tough trees can handle most the complications that nature throws at them. They can handle drought, storms, heat, weather extremes, flooding, and sudden drops in temperatures. But not all trees fit into this ideal. Only a handful of North American native trees and a few aliens can handle all these stressors and thrive. But what are those tough trees? Where do we find them? And what problems do they have, if any?
Diversifying the Urban Forest
What is the urban forest and why do we need to diversify it? The urban forest is the genera and species of trees that cover a city’s surfaces with leaf canopy, both deciduous and evergreen. But why diversify it? Because we live in an ever-changing landscape, fraught with native, alien, and incoming problems. Inside a city’s urban forest there is already many problems. Poor planting issues, root problems, fungal and bacterial diseases, insect pests, mechanical blights, and weather-related issues are all common.
We as community foresters, arborists, gardeners, and homeowners, all need to play an active role in managing these issues, as well as in providing new life to the urban forest with diversification. Adding tough trees to the mix will not only alleviate many of the current problems, but it will also reduce the potential for future problems.
Most of our urban forests are chock full of only a few genera, and many species take up too much room. According to the Kansas Forest Service, any one species of tree should not cover more than 10% of the canopy of a city. Problem example: Hiawatha Kansas is known as the City of Beautiful Maples because of their large sugar maples. But the sugar maples cover roughly 37% of the urban forest canopy of Hiawatha, and that is 27% too much. I do not have anything against maples, but a healthy urban forest should have more diversity.
Identifying Problem Areas within the Urban Forest Canopy
Knowing whether you need to diversify your canopy is the first goal. By doing a tree inventory, if you have not already done so, should be your first objective. Having the help of a qualified arborist in not only identifying trees, but assessing them for structural or pest problems is essential. You can find certified arborists for your area by clicking here.
A tree inventory can not only point you in the direction of what trees you have, but what you need to add to make your urban forest more diversified. A tree inventory should include the tree species, number of individuals, tree size (diameter), % of tree conditions, and %of total trees per species. It might look something like this.
This is a tree inventory I did on my own property to assess my private forest canopy. Now that I know my trees, and their overall health, I can continue to diversify my forest.
I have a list of 40 species of trees that are tough trees for Kansas and Nebraska landscapes. These trees grow best in Zones 5 to 8, and can handle a wide range of issues. There are some naysayers within the forest service itself regarding a few of these trees, but in my experience they are biased against them for the wrong reasons. For example, the hackberry is often disregarded as a good tree for the urban forest because it has a tendency to get galls on the leaves and there has been some freak damage reports. But I have had hearsay on those reports, no first-hand accounts.
The list is broken into 4 categories.
- Native shade trees
- Native understory or ornamental trees
- Commonly planted natives
- Introduced (Alien) tree species
Now, just because a tree species is commonly planted does not mean you cannot plant one. Just be careful not to overplant and have more than 10% of your canopy in those species. The oaks do have some potential issues, but as long as the individual trees are kept as healthy as possible, then you are likely to keep diseases and insects at bay. Also, many of the older oaks, maples, ash, and elms of our urban forests have these issues because they are older and have been neglected.
Native Shade Trees
In this group there 17 species of shade type trees, all of which are not widely planted, but are considered tough trees. Some have individual issues, like a specific pest or disease. But most have few if any problems. Also, just because a tree is not on this list, does not mean you cannot plant it. You are welcome to try any tree you would like. Just be aware that it may have issues beyond your level of management or control.
American Hornbeam – Carpinus caroliniana
One of the smaller shade type trees, hornbeam, aka musclewood, grows only 30 feet tall and wide. It is native throughout the eastern US, from the Missouri River east. The leaves of the hornbeam resemble an elm, and they are in the same family as elms and hackberries. In the fall, leaves turn orange, red, or yellow. Hornbeams prefer moist, acidic, well-drained soils. But according to Michael Dirr, they perform remarkably well in the hostile environments of the Midwest. Its only problem appears to be a desire to resist transplanting.
- ‘Native Flame’ – this cultivar from J. Frank Schmidt grows 30 feet tall by 30 feet wide. The leaves turn brilliant red in autumn.
- ‘Firespire’ – selected in Minnesota for cold hardiness and an upright form, this cultivar grows 15 feet tall and 10 feet wide. The leaves turn reddish-orange in fall.
Bitternut Hickory – Carya cordiformis
A little known tree outside of foresters and native plant enthusiasts, the bitternut hickory grows straight with a good central leader. Even in the open I have seen nice specimen of this native tree. One of the problems associated with the hickories is the difficulty in transplanting, solved by growing them by seed in containers, rather than trying to graft onto rootstocks. This hickory grows 50 to 80 feet tall and 50 feet wide. The leaves turn yellow gold in autumn. It has no major pests.
Pecan – Carya illinoiensis
One of the mightiest trees in the forest, the pecan is a benefit to the gardener and wildlife alike. Native in the Southern Great Plains and Gulf Coast States regions, it grows 60 to 100 feet tall and wide. Besides being grown in large plantations for nut, the wood is also prized for many things. I know of several older pecans in neighborhoods around Northeast Kansas. My brother-in-law has 2 pecans in his yard, which were planted by his grandparents over 50 years ago. They can be slow-growing trees, similar to oaks, but are worth the process. Pecan trees are tough trees, growing and fruiting when other trees are failing. Almost all of the specimens I know of are in tough sites.
It is best for nut production to have 2 cultivars for cross-pollination. And, if you want to have regular nut production you must spray the leaves in mid spring with Zinc to promote nut retention and growth. Zinc is depleted from the tree after each crop of nuts. There are many cultivars available.
Shagbark Hickory – Carya ovata
Just like the bitternut hickory, most communities may have few of these unless planted by squirrels or jays. Hickories are great trees, and a diverse group, but they are rarely planted in urban areas. The shagbark is one of my favorite trees. I have an older one in my front yard, and I always enjoy searching the leaves for galls and caterpillars. The nuts are sweet and different from other nut producing trees. Shagbarks grow 60 to 80 feet tall and 30 to 50 feet wide. The bark is one of its best features, peeling off in large strips, hence its name. The leaves of all the Carya are compound, and shagbark has the fewest number of leaflets of any, with 5 to 7.
There are no cultivars available. This is primarily because seedling are incredibly slow to get going. While little to no research has been done on the subject, I suspect that they spend extra time developing their root systems before producing upward growth. You can get seedling grown trees, but I would be more inclined to grow them by seed only, planting seeds where I want the trees to grow.
Northern Catalpa – Catalpa speciosa
From afar it looks like a tropical totem pole. This is because the catalpa is has some of the largest leaves on a tree in the temperate zones of the world. Larger leaves usually remind one of tropical rail forests. The last tree was one of the slowest growing (shagbark hickory) and the catalpa is one of the fastest. I have seen specimens grow as much as 6 feet in one season, before slowing down when they near mature height. They grow 40 to 60 feet tall and wide, though many of them do not grow very wide at all.
Besides it quick growing habit, the flowers are the next best thing. They look like tropical orchids. And they are very fragrant. Following the flowers are long green pods, which have been used by little boys as swords. I have done so with my cousins growing up. Catalpas are very tolerant of soil pH whether high or low, drought, and extreme heat.
- ‘Heartland’ – is a nice upright, narrow selection for city street, despite its messy pods and flowers. It grows 50 feet tall by 25 feet wide.
Southern Catalpa – Catalpa bignonioides
Sometimes I call it the other catalpa. When I come across specimens that look different than our regular northern catalpa, I say it must be the other catalpa. It was that way when I found what once was the Kansas State Champion northern catalpa (unofficial, they cut it down before the state could measure it), I thought so because it was wider than it was tall. Southern catalpas grow 40 to 70 feet tall and wide. It is just as drought, heat, and wet tolerant as its cousin above.
Hackberry – Celtis occidentalis
This is one of my all-time favorite trees. I love hackberries! Although, I wish they had a different common name. And for tough trees, this one if probably the best. They are adaptable to a wide range of conditions, from drought to flooding, from hot to cold, and different soil types. Maybe this is why they do so well here in the Central Great Plains. The only real problem is that they are not a pretty tree. But that can be overlooked for their durability.
Hackberries grow in a vase or rounded form, typically 50 to 70 feet tall and wide, though much large specimens are common. There is a huge one at the Courthouse square in downtown Hiawatha, KS, which is around 80 feet tall and 60 feet wide. And it is not even the state champion! Besides toughness, hackberries are home to a lot of insect diversity. At least 5 butterflies use the leaves for their caterpillars, along with many moths. And there are dozens of gall wasps, gall psyllids, and other insects which feed on the tree. Birds and other wildlife dine on the fruits, which are astringent to humans.
- ‘KC Streetview’ – a cultivar introduced by Doug Grimm which was taken from the state champion. A nicely shaped tree, fast growing, 60 feet tall and wide.
- ‘Prairie Sentinel’ – discovered in Western Kansas, this hackberry has a narrow, upright form, growing 45 feet tall by 12 feet wide, great for downtown areas.
Sugarberry – Celtis laevigata
Similar to its cousin the hackberry, sugarberry is a tough tree for landscapes. Despite being more common in the Southeastern regions, and native of bottomlands and swamps, it does very well as a street tree in a tough spot. Here in the Central Great Plains I have found large specimens growing on upland slopes, where water never pools. It does grow smaller than hackberry, only 40 to 50 feet tall and wide. But it too hosts 5 butterflies and a range of moths and other insects. Cultivars are mostly non existant.
Persimmon – Diospyros virginiana
A most remarkable tree. And it certainly belongs in a list of tough trees. Besides being adaptable to heat, cold, drought, wet, acid, alkaline; it has edible fruit and valuable lumber. And almost no problems. The only problem I foresee as a urban tree is its tendency to sucker and form colonies. But I have only see this tendency in a few places. I have known many large, single trees in landscapes and wild areas. The fruit is extremely astringent when unripe, but tasty and different when ripe.
Young persimmons are very fast growing, reaching 20 feet tall in less than 7 years. As they get taller, they do slow down some, and become great trees. The bark alone is worth growing them for. Trees are narrower, but great for shade, growing 30 to 65 feet tall by 20 to 40 feet wide. The leaves are simple and usually stay dark green. At least 17 species of moths use it as a host plant, and deer and other animals eat the fruit. Their are several cultivars available.
Kentucky Coffeetree – Gymnocladus dioicus
This and the hackberry are my 2 favorite trees. Although, I do like a lot of other trees almost as well. But while I like the hackberry for its versatility and insect hosting, I like the coffeetree for its lack of insects. The Kentucky coffeetree got its name for the seeds found in the large black pods, which, when roasted and ground, do form a substitute for coffee. The leaves are bi-pinnately compound, and are very tropical looking. Also, they are extremely adaptable and tough in a wide range of conditions.
Kentucky coffeetrees are dioecious, meaning that male and female flowers are on separate trees. So, if you want to get the tree with no pods, choose a male cultivar, which is a clone of a male tree chosen for other characteristics as well. I have 3 trees currently in my landscape, a cultivar called ‘Espresso’ and to seed grown trees. When they are young, the trees are spindly with few branches. But as they mature, especially out in the open, they become well-rounded and nicely shaped. They can grow 60 to 80 feet tall and 40 to 80 feet wide.
- ‘Espresso’ – a popular cultivar which grows relatively fast and develops a rounded crown, 55 feet tall by 40 feet wide.
- ‘Skinny Latte’ – a narrow cultivar from the Morton Arboretum, growing 50 feet tall by 20 feet wide.
- ‘True North’ – a nice upright selection from Minnesota with excellent cold hardiness, growing 55 feet tall by 30 feet wide.
Osage Orange – Maclura pomifera
One of the best and most under-utilized trees for the urban canopy. It belongs on a tough trees list too. Sure, some have fruit and thorns, but there are cultivars that are free of both. Or, you can try cultivars with smaller or larger fruit. Osage orange is not an orange tree at all, but a great tree for tough sites. It is tolerant of high pH soils, flooding, drought, and heat. Originally used to build windbreaks and thorny cattle barriers, it is mostly used now for shade trees, fence posts, and firewood.
It is a fast growing tree; I have observed as much as 3 to 5 feet of new growth per year. It grows to 50 feet tall and wide, with many specimens doing more. A large one on the corner of my property, indeed the property marker, is 65 feet tall and 30 feet wide. The leaves are dark green and shiny. Several moths use it as a host plant.
- White Shield’ – the most popular cultivar which is both seedless and thornless. Its a great street tree, growing 35 feet tall and wide.
- ‘KC Fence Post’ – a thornless and fruitless variety from Doug Grimm.
Eastern Red Cedar – Juniperus virginiana
Only one of two evergreens on this list, the red cedar is not a true cedar, but a member of the junipers. And while it is not generally considered an urban street tree, it does make a handsome shade tree even when young. Typically used in windbreaks, it has a dense canopy which is great for nesting birds. Red cedars grow 40 to 50 feet tall and 20 to 40 feet wide. Their only major pest is bagworms, which do not occur in large numbers yearly, but more on a 1 out of 4 years cycle.
Sycamore – Platanus occidentalis
Generally considered a stream bank edge tree, they are remarkably drought and heat tolerant. The large leaves resemble maple leaves, but are 4 to 5 times larger. Sycamore trees are tough trees, they bend and sway in the wind, dropping dead or weak branches so they do not hinder the overall structure of the tree. They can get quite large, 60 to 100 feet tall and wide, but are also long-lived.
In the urban canopy they should be delegated to parks and walking trails, where they can shade people going about the day. Along streets is not recommended, as they drop a lot of sticks, and the leaves and seed balls can be messy. They have no major pest problems, but do get aphids, lacebugs, and other insect pests often. A number of moths feed on the foliage.
- ‘KC Snow’ was selected for its white patterned bark which runs from the canopy to the roots. And, the original tree is growing in a very tough spot, in the middle of a circular driveway.
Quaking Aspen – Populus tremuloides
This is probably one of the narrowest shade trees, but when planted in groups of 3 or more, they can present plenty of shade. And the sound of the leaves rattling in an afternoon breeze is quite refreshing. Most grows 30 to 40 feet tall by 10 to 15 feet wide. While the species in general prefers cooler summers, most are adaptable to the heat and drought of the Central Great Plains.
- ‘Prairie Gold’ – a selection from the Nebraska Statewide Arboretum, has better drought resiliency than the native species. In the 10 years we have had it here, I have not seen the pest problems touted by other agencies. It is relatively low in problems compared to other aspens. There are several moths which us it as a host plant.
Baldcypress – Taxodium distichum
Another one of my favorite tough trees. I love the baldcypress. Looking like an evergreen when in full leaf, it is actually a deciduous conifer. It grows 50 to 100 feet tall by 30 to 50 feet wide. A favorite plant for places of standing water; they are incredibly drought and heat tolerant. Even moderately high pH soils are okay for these great trees. It has few problems, mainly bagworms which cause no permanent damage.
- ‘Shawnee Brave’ – grows 75 feet tall by 25 feet wide with dense, dark green needles. One of the most uniformly shaped cultivars of any.
American Linden – Tilia americana
In recent years, Japanese beetle has wrecked havoc on our introduced littleleaf lindens. But surprisingly, our native species rarely sustains any damage at all. And they are prized by beekeepers for the nectar which bees take up during flowering. The leaves are large and heart shaped but not uniform. The American linden is very drought, heat, flood, and cold tolerant. And it can handle various pH levels. At least 25 moths use it as a host species. It grows 70 feet tall by 50 feet wide.
- ‘KC Beekeeper’ – an excellent selection from Doug Grimm, with dark green leaves and a nice shape, growing 60 feet tall and 40 feet wide.
American Elm hybrids – Ulmus americana
The American elm once dominated the landscape from the Great Plains to the Eastern seaboard. It was the ideal tree for the urban landscape: disease resistant, heat and drought tolerant, and had few pests. The Dutch elm disease (DED) came and wiped almost all of them out. Now, American elms are making a comeback. With renewed interest, and breeding programs, there are American elms ready to be planted in the urban canopy once again, resistant to DED.
The American elm grows 80 to 100 feet tall and wide. It does have some other pests and diseases, not considered to be problematic at this time. A few butterflies and several moths use it as a host plant.
- ‘Prairie Expedition’ – grows 65 fee tall and wide. It is very cold hardy, possibly to Zone 2.
- ‘Princeton’ – the most widely planted and recommended of all new cultivars. It grows 75 feet tall and 50 feet wide.
Native Understory Tough Trees
What are understory trees? These are smaller, ornamental or non-shade trees which grow under larger trees and typically prefer to be shaded, especially as they are growing. Once they are established, they can generally handle full sun. I have 6 tough trees on this list.
Redbud – Cercis canadensis
While this is one of the more commonly planted small ornamental trees, there is still room for planting more. Redbuds are adaptable to a wide range of soil types, and are heat and drought tolerant. Besides the typical red or pink flowers, they can also be white. Trees typically grow 20 to 35 feet tall and wide. Its one of my favorite small trees for moths, and several including the redbud leaffolder are cool to see.
- ‘Raspberry Twinkles’ – one of ,y favorite go to cultivars, the original was selected in the wild outside of Nebraska City. It grows 20 feet tall and wide.
- ‘KC Miss America’ – a seedless, white-blooming selection from Doug Grimm. Grows 18 feet tall by 25 feet wide.
- ‘Forest Pansy’ – hardy only to Zone 5b, it has purple green foliage, turning all green in full sun. It grows 25 feet tall and wide.
- ‘Ruby Falls’ – a weeping variety with purple leaves which holds color even in full sun.
Eastern Wahoo – Euonymus atropurpureus
A small tree to large shrub, wahoo is an interesting native replacement for burning bush. It grows 10 to 30 feet all and 5 to 15 feet wide. The brown-red flowers actually smell like rotting carrion, and are pollinated by flies. Fruits are bright red and usually eaten by birds. The leaves and shiny green, turning brilliant red in autumn. A great tree for understory or part sun.
Hophornbeam – Ostrya virginiana
One of my favorite small understory trees, it has soft leaves and hard as nails wood. Also called ironwood, this tough native tree grows 40 feet tall by 30 feet wide. But here in Kansas, it needs to be planted where it will receive protection from afternoon sun. The fruits or seedpods look like clusters of the hop vine fruits, hence its name. The bark can become shaggy as the tree ages.
Blackhaw Viburnum – Viburnum prunifolium
I planted this large shrub or small tree on the edge of my driveway, between an apricot and my Monarch Waystation. Once it reached 8 feet tall, I have had a cardinal nesting in it. Besides the benefit for nesting birds, blackhaw has dark blue edible fruit, and some of the best reddish fall color. It grows 15 to 20 feet tall by 15 feet wide, and can form a thicket if suckers are not pruned away.
Wafer Ash – Ptlea trifolia
One of the more unknown small trees in our area, wafer ash is a great tree for butterflies. There are 5 species of butterfly which use it as a host plant, including the eastern tiger and giant swallowtail. It only grows 15 to 25 feet tall and wide. If you would like to see a nice specimen, there is one on the south side of the Jackson County Courthouse, east side of the door, in Holton, KS. Wafer ash is actually a member of the citrus family, a distant cousin of lemons.
American Bladdernut – Staphylea trifolia
Another one of the more unknown tough trees. American bladdernut is a unique understory tree, growing just 10 to 15 feet tall and wide. Although it is small, its bell-shaped flowers are great for early foraging bumblebees. The fruit is a 3-cornered pod which contains the seeds, and looks like a bladder. Besides being very different, this tree is great for nesting birds, many of which prefer to be at a height of 10 to 12 feet off the ground.
Commonly Planted Native Trees
These trees can be found in almost every city’s urban forest. They are the trees that for most homeowners, and a lot of city planners, are the go-to trees for new plantings. Unfortunately, when comparing these to other tough trees, these usually when in regards to fall color and popularity, as well as ease to find in the nursery trade. A lot of the above trees can be difficult to find. In some cases, these commonly planted trees take up 30 or more percent of the total amount of trees in the urban forest, way too much. There are 8 trees on this list (sugar maple, red maple, hybrid maple, and the first 5 oaks mentioned).
Sugar Maple – Acer saccharum
Here in Northeast Kansas, these trees are definitely overplanted. And that is too bad, because they are such wonderful and hardy trees. But all of the maples are overplanted, especially red and hybrid maples. If Asian longhorned beetle becomes a problem in our area, maples are the first trees they will attack. Sugar maples are tough trees otherwise, being quite tolerant of heat, drought, excessive rain, and cold. And they thrive in a range of soil pHs.
If you must plant sugar maples, then do not plant more than 1 of them on your property. Or at least, make sure that you have less than 5% of sugar maples on your property inventory, if you have more than a normal city lot. For an average city lot, do not plant more than 1 sugar maple.
Oaks – Quercus species
All of the oaks are overplanted, except maybe dwarf chinkapin oaks. And that may be one of the reasons we have so many problems with our oaks. Oak decline, bur oak blight, oak wilt, and many other things contribute to the death and decline of oaks. They can be great trees, able to withstand a range of soil and site conditions, sometimes living for centuries. But overplanting leads to many of the problems, causing rapid decline and death. If you must plant an oak, and I love oaks, then choose a species which is underplanted in your area.
Oaks which are overplanted include:
- Bur, Q. macrocarpa
- White, Q. alba
- Red, Q. rubra
- Willow, Q. phellos
- Pin, Q. palustris
Oaks which are underplanted in most situations include:
- Shingle oak, Q. imbricaria
- Shumard oak, Q. shumardii
- Dwarf chinkapin, Q. prinoides
- Post oak, Q. stellata
Introduced (Alien) Tough Trees
The following list of tough trees includes 9 species of introduced trees which can benefit the diversification of the urban forest. Some of the these are relatively unheard of outside of tree collections or arboretums. Other are planted for their ornamental value, but not in great numbers. On the east half of the US, some of these trees may become or are listed as invasive, but here in Kansas and the Central Great Plains, they are not a problem. Always be careful when planting introduced species, because like the callery pear, they have the potential to be a problem.
European Hornbeam – Carpinus betulus
I do not see much of these trees, mainly because most of the nurseries I frequent do not carry them. But they are tough, being able to withstand urban conditions, heat, drought, rain, and pollution. It can be somewhat slow growing, but a very nice tree at 50 feet tall and 40 feet wide when mature. In Europe it is often pruned into hedges or screens, and takes to being used this way well. A customer of mine planted a row of hornbeams around his pool for screening.
- ‘Emerald Avenue’ – fairy common cultivar growing 40 feet tall by 25 feet wide.
Hardy Rubber Tree – Eucommua ulmoides
I first became aware of this tree when I started at Grimm’s in 2011. Doug Grimm introduced me to this tree and I have found it to be a very good recommendation for tough sites. It is very drought and heat tolerant, though it cannot take standing water. Also, it is tolerant of a wide range of pH soils. Hardy rubber trees grow 50 feet tall and wide.
Maidenhair Tree – Ginkgo biloba
Where the name maidenhair came from I do not know. In the Central Great Plains, the ginkgo can be found in every town, but not in any overwhelming numbers. I know of several nice specimen trees in almost every small town in Northeast Kansas. Even the tiny, unincorporated town of Willis in Brown County has a nice one. The ginkgo is pest and disease free, grows decently fast once the roots are established, and has great fall color (yellow). The only downside is that seed grown trees can be either male or female, and female trees have a round fruit, which stinks as it rots away. So choose a male cloned cultivar. They grow 100 feet tall and 60 to 80 feet wide.
- ‘Autumn Gold’ – this is a nice male selection, growing 50 feet tall by 30 feet wide.
- ‘Presidential Gold’ – another favorite, growing 60 feet tall by 40 feet wide.
- ‘Princeton Sentry’- the standard for columnar ginkgos, growing 60 feet tall and 25 feet wide.
Seven Son Tree – Heptacodium miconoides
This is probably my favorite small introduced tree. I recommend it to anyone looking for a 3-season ornamental tree for a small site. It grows 15 to 20 feet tall by 10 to 15 feet wide. It has 3 seasons of interest, including early leaf formation, fall flowering, and peeling bark for winter. In the fall when it flowers, bees, butterflies, and beetles are seen on the pure white flowers.
- ‘Temple of Bloom’ – a Proven Winners cultivar which gets 10 feet tall and wide, more compact than the species.
Star Magnolia – Magnolia stellata
I love magnolias, but many of them are not tough trees, needing either sun or heat protection, or more water during drought. We have some beautiful native magnolias, they just like more water. But star magnolias can fit into almost any garden in the US. They are hardy in Zones 4 to 9, and drought and heat tolerant. Everyone should have one in their landscape. And adding them into the urban canopy can increase biodiversity. They grow to 20 feet tall and wide.
- ‘Centennial Blush’ is a pink flowering, double flowered cultivar. It grows 20 feet tall and wide.
- ‘Royal Star’ is one of the most popular cultivars, with white flowers, growing 15 to 20 fee tall and wide.
Norway Spruce – Picea abies
The other evergreen on my list. Here in Northeast Kansas, most evergreen trees struggle. Either because we have such temperature swings in the spring or fall, or because of our tendency to have droughts, I do not know. But the Norway spruce does seem to be more hardy here. I know of some immense specimens that were planted decades ago, and have never shown any of the problems shown with blue or white spruces. Farther south is may suffer from heat, but that may also be attributed to decreased humidity, unlike here. They grow 60 to 200 feet tall by 30 to 80 feet wide, depending greatly on location.
Chinese Pistache – Pistacia chinensis
This is another tree that Doug Grimm introduced me to. And, after a n older specimen was found growing at the Mitchell County Courthouse in Central Kansas, I know they are tough trees. I come from that area, and if you are a tree out there, you have to be ready for extreme drought, wind, rain, hail, and heat. One thing it does not like is standing water, so avoid low areas and ditches. It grows 30 to 50 feet tall and wide.
Japanese Pagodatree – Styphnolobium japonicum (Sophora japonica)
I first mistook these trees in my grandparents collection for western soapberry. But the flowers showed the difference. In the landscape, they grow 60 feet tall and wide. And they are tough, adapting to a wide range of soils, are heat and drought tolerant, and have few if any problems. The flowers are somewhat fragrant, and attractive to bees.
Japanese Tree Lilac – Syringa reticulata
When it comes to lilacs, I like these over the shrub types. Tree lilacs are maybe a little less fragrant, but they are great for pollinators. I have watched the bees, butterflies, and wasps flock to an older specimen in a cemetery in central Brown County, KS. The usually grow 25 feet tall and wide. They are susceptible to lilac borers, just like the shrub forms, but I rarely see enough damage to kill an entire tree.
- ‘Ivory Silk’ is the most popular cultivar, growing 25 feet tall by 15 feet wide.
There are a lot of trees you can add to the urban canopy to increase biodiversity. But these tough trees are recommended for the worst environments. Here in the Central Great Plains region, we need these tough trees to counter our high pH soils, extreme heat and cold, high winds, and drought conditions. There are a lot of trees to choose from however, and finding trees is not as difficult as it might seem. Most nurseries carry a variety of these trees, although some can be difficult.