Gardening Basics

Tough Trees

For really difficult sites, consider one of these stout species.

By Marie Hofer
Filed under: Trees, Garden Zones, Plants

Red maples are often listed as great city trees and they are — as long as the soil isn't compacted, air pollution isn't high, and there's a steady supply of water. Here, 'Autumn Blaze.' (Photo by Michael A. Dirr)

Life on the street isn't easy — just ask most trees that have to duke it out with ozone, exhaust fumes, soil compaction, drought stress and too much pavement. They'll show you dying branches, diseased foliage, early leaf drop. It's hard to find a tree that will put up with every tough condition and remain flawless themselves. The red maple, a beautiful tree, doesn't deal well with either pollution or compacted soil, and the gingko, great at handling pollutants and almost any soil, can be a little gawky in winter, and the female drops smelly fruit. Although the following so-called "street trees" aren't perfect, they'll put up a good fight and still look good:

Littleleaf linden (Photo by Michael A. Dirr)

Littleleaf linden (Tilia cordata). One of the best at standing up to pollution, the linden is also tolerant of a wide range of soil conditions--acid to alkaline (Moist, well-drained and rich soil results in the best growth, however). It's quite large (60 to 70 feet) and its dense canopy, broadly pyramidal as the tree ages, begins close to the ground. (In its native Europe, the linden is widely used for hedging as well as for shade.) Yellowish fragrant flowers appreciated by bees appear in early summer.

Littleleaf linden, in late June (Photo by Michael A. Dirr)

Leaves are dark green and lustrous, sometimes turning a soft yellow in fall. This tree is something of a shedder — flowers, seedpods, etc. — so unless you want to spend the summer and fall sweeping, don't locate it over a walkway. Better yet, site it in a large lawn area and don't limb it up; there won't be nearly as much litter that way, and you can simply mow what may fall outside the perimeter of the tree. There are lots of good cultivars — 'Greenspire', which has a good central leader and is a little smaller (40 to 50 feet), is widely available in the trade. Zones 3b to 7.

European hornbeam (Photo by Michael A. Dirr)

European hornbeam (Carpinus betulus). A wonderful landscape tree, the European hornbeam is good for a variety of uses — privacy screen during the growing season, softening the edges of large buildings. Easily pruned, it too is used for hedging in Europe. The species is 40 to 60 feet tall and 30 to 40 feet wide, but there are smaller cultivars; 'Fastigiata', whose branches angle up, grows to only 30 to 40 feet tall and 2/3 as wide. An excellent form, fine texture in summer and winter, lovely clean foliage and resistance to pests and disease are what sell this tree. Zones (4)5 to 7. Bears nutlets in the fall.

American hornbeam, bark

American hornbeam or blue beech (Carpinus caroliniana). Also called musclewood for its smooth, sinewy gray limbs, this small native is often found in moist, rich soils in the wild, but don't let that fool you; it can handle heavy clay soil and tough urban conditions (as well as shade, drier soils and occasional flooding). Fall color is yellow to reddish. Mature size, 20 to 30 feet. Zones 3b to 9. Keep it away from paths, because of nutlets in the fall.

Panicled goldenraintree (Photo by Michael A. Dirr)

Panicled goldenraintree (Koelreuteria paniculata). This tough little tree tolerates pollution, heat, drought and a wide range of soil conditions. Where it's hardy, it's used widely as a street or commercial-zone planting with great success. In early to midsummer, it literally drips with foot-long panicles of yellow flowers that hold for several weeks. The flowers are replaced by papery seed capsules which persist on the tree for months, slowly changing from green to yellow to brown (the tree looks a little unkempt when the seed pods are brown). Mature size, 30 to 40 feet. Zones (4) 5 to 8.

Black tupelo, in fall (Photo by Michael A. Dirr)

Black tupelo (Nyssa sylvatica). Also called black gum or sour gum, this tree is a mixed bag: it's rated excellent for tough landscape conditions but can't handle pollution. On the plus side, it's very adaptable to soil type — moist or dry — and it offers brief but utterly spectacular red fall color. It tends to get leaf spot; look for resistant varieties. Make sure to give this tree good drainage. Mature size, 30 to 50 feet. Zones 4 to 9.

Lacebark elm (Ulmus parvifolia). Common names can be very misleading and nowhere is this more true than with the lacebark elm, or Chinese elm. But don't confuse this with the Siberian elm (Ulmus pumila), which is often mistakenly mislabeled Chinese elm. Ulmus parvifolia is a far superior specimen that can put up with the likes of drought, heat and poor soils (and it's resistant to Dutch elm disease). Among its attributes: broad crown with slightly pendulous branches, small leaves (which give it a fine-textured appearance) and especially its exfoliating multi-colored bark. The species is 40 to 50 feet tall and wide, and cultivars offer a wide range of cold tolerance, shape and fall color. Zones (4)5 to 9 for the species. 'Drake' goes from Zones 7 to 10.