Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
7/15/02
Contacts:
Mark Gleason, Plant Pathology, (515) 294-0579, mgleason@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033,
jmcguire@iastate.edu
Yard and Garden Column for the Week Beginning July 19, 2002
A Few More of My Favorite Trees
By
Mark Gleason
Extension Plant Pathologist
Iowa State University
A few weeks ago, my column praised five terrific trees for Iowa landscapes. These fab five were culled from my 17 years of tree-troubleshooting experience in the state.
Some wonderfully hardy, reliable, beautiful trees for Iowa were on that list: white pine, Kentucky coffee tree, Norway spruce, crabapples and Japanese tree lilac. But five superior trees aren't enough. Here are five more of my favorites.
Heading the honor roll this time is serviceberry (Amelanchier arborea).
Call it a shrub or a multistemmed tree, it's hard to over-praise this
wonderful Iowa native. Thanks to its small stature - it rarely tops 25
feet- and slender profile, serviceberry fits neatly into many urban landscapes.
Serviceberry is a year-round pleasure. In the early spring, before much
else is blooming, its cloud of white flowers is a marvel to behold. When
the small fruit ripen in June (the plant is also called Juneberry for
this reason), they draw flocks of robins, orioles, waxwings and other
birds.
Serviceberry leaves turn an attractive red in the fall. In winter, the graceful, interwoven, silver-gray branches delight the eye. To top it off, serviceberry establishes reliably in many soil types and is nearly free of serious disease and insect problems.
At first glance, baldcypress (Taxodium distichum) seems an unlikely choice for Iowa landscapes. A hot lawn in Ankeny is a long way from Cajun country. But baldcypress is surprisingly cold hardy and adapts well to all sorts of urban sites.
Even more surprising is baldcypress' habit of dropping all its needles in the fall. Among the conifers, only larch and baldcypress can manage this trick. Luckily, the reddish bark, strikingly pyramidal shape, and fine-textured twigs are attractive in winter. During the growing season, the soft needles create a delicate, almost Oriental appearance.
Baldcypress grows fairly slowly on many Iowa sites, but can eventually reach a height of 60 feet. Disease and insect problems are minimal. Like Kentucky coffee tree, baldcypress is an under-planted species that deserves a place in many more Iowa landscapes.
My next choice, black walnut (Juglans nigra), will cause some readers to doubt my sanity. What's so great about a tree that loses it leaves early in the fall, drops large green nut husks that spin out of a lawn mower like shrapnel and poisons other plants?
Admittedly black walnut has a few problems. The nuts can be annoying, and some plants can be injured by a substance called juglone that leaks from a black walnut's roots, leaves, husks and branches. For an Iowa list of plants that are sensitive and resistant to juglone, see the walnut article at: http://www.ipm.iastate.edu/ipm/hortnews/2002/6-14-2002/juglone.html.
Black walnut's virtues outshine its drawbacks. A large native tree, walnut develops a corrugated bark and gnarled branching pattern as striking as bur oak - which many people, including me, consider to be the most beautiful of all native Iowa trees. Black walnut's fine-textured foliage provides a light, dappled shade. It suffers from no major disease or insect problems. In the right site and situation, it's a truly outstanding tree.
Northern catalpa (Catalpa speciosa) is my sentimental favorite. Widely planted throughout the Midwest by European settlers, it has since declined in popularity in urban landscapes. Like black walnut, it carries some baggage.
First, the baggage. Catalpa is a large tree, demanding a site bigger than some modern backyards. And its large leaves and long, bean-like pods create many opportunities for raking.
What's to like about catalpa? It's a spectacularly beautiful tree. Its masses of white flowers in the late spring create a luxuriant, almost tropical effect that outshines all other midwestern trees. Some of the bean pods remain attached throughout the winter, creating a striking silhouette. Add in catalpa's gnarled branches and large leaves, and you have a tree with a wonderful, distinctive personality. Once again, diseases and insects aren't major concerns.
Finally, consider the ginkgo (Ginkgo biloba), also called the maidenhair tree. Ginkgo is an ancient tree whose ancestors shaded the dinosaurs nearly 100 million years ago. On its long evolutionary path, ginkgo has devised potent defenses against virtually all insects and diseases.
Ginkgos thrive in almost any Iowa site and soil type. They grow fairly slowly here but eventually can reach 50 to 80 feet. Their beautiful fan-shaped leaves create an open shade and turn a bright yellow in the fall.
One caution: Make sure you buy male rather than female ginkgos, because the females produce numerous fruits that fall to the ground and create a memorably nasty smell as they decay.
In Iowa's challenging climate, it makes sense to plant trees that can tolerate everything nature can dish out - including insect pests and diseases. All 10 of my favorite trees are not only tough but are also attractive and distinctive. I hope that some of these superior trees find their way into your landscape.
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ml: isugarden
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