Forest and Shade Trees of Iowa

Part 3: Growing Trees in Iowa

378 n a t u r a l h i s t o r y a n d u s e s o f i o wa’s t r e e s The arrowwoods are medium-size to large shrubs of upland woods and edges. As a group they are easily recognized by their roundish, coarsely toothed leaves, but their taxonomy is complex and the species are not easy to sort out. Native species include the downy arrowwood, found across much of the state but more common to the east; the Kentucky viburnum, rare in southeast and southwest Iowa; and the southern arrowwood, uncommon in the southwest part of the state. The highbush cranberries have bright red fruits that persist on the branches and remain colorful all winter. Their leaves are lobed, resembling those of maples. The American highbush cranberry is native on moist wooded slopes in Iowa’s northeastern corner; two other Eurasian species are planted. The leatherleaf viburnums are tall shrubs with large, thick, dark green leaves that often persist into early winter. None is native to Iowa, but the wayfaring tree from Europe is frequently planted, especially its cultivar ‘Mohican.’ One other native species, the blackhaw, occurs here and there in eastern and southern Iowa. It is useful for landscaping and can be trained as a small tree. Prickly-ash, Zanthoxylum americanum Mill. Prickly-ash is a spiny, colonial shrub growing 4 to 12 feet tall, common throughout Iowa in clearings, open woods, and wood edges in both wet and dry soils. Its individual stems are often treelike in habit if not in height. Prickly-ash is sometimes called toothache tree because its tiny fruits numb the mouth and lips when chewed, thus providing relief from toothaches. The leaves and the leathery rinds of the fruits contain tiny oil glands that produce a citruslike aroma, indicating the relationship of this species to the lemon and orange. The bark is also aromatic and was once used as a stimulant and as a home remedy for flatulence and diarrhea. PromisingTreesforIowa Diversity is the key to a healthy landscape. Too great a reliance on one species can lead to disaster if a new disease or insect pest appears. Iowans learned that lesson many years ago with the American elm, and it appears we may learn it once again with the green ash. Native species should always be the backbone of a community forest, but there are trees from other parts of the world that grow well here and add variety to our landscapes. A few of these, such as the blue spruce and Norway maple, have been so widely planted that they are perhaps too familiar. Others, such as the Austrian and Scots pines, were much planted in the past but have proved susceptible to diseases or insects. Many other fine trees, however, are greatly underutilized. In today’s smaller urban spaces, there is a need for smaller trees. Unfortunately , Iowa has few native trees that remain modest in size and are also useful for landscaping. There are some, to be sure—redbud, serviceberry, and ironwood among them—but there is a need for more variety than our natives provide . It is in this size range, then, where introduced species can be especially helpful. To find useful new trees, Iowa’s arboretums are testing species from other parts of the world. Desired traits include tolerance of winter cold, adaptability to varied soil types, resistance to disease and insects, and year-round beauty. It is also essential that these new trees mind their manners and not become weeds. As time goes on, we will know more about which new species are best suited to Iowa. In the meantime, a few are promising enough that we can recommend them for planting. For the homeowner who likes something unusual, these fine trees may fit the bill: Paper-bark Maple, Acer griseum (Franchet) Pax Three-flower Maple, Acer triflorum Komarov Nikko Maple, Acer maximowiczianum Miquel (A. nikoense Maxim.) Korean Maple, Acer pseudosieboldianum Komarov Miyabe Maple, Acer miyabei Maxim 380 n a t u r a l h i s t o r y a n d u s e s o f i o wa’s t r e e s Purpleblow Maple, Acer truncatum Bunge Japanese Horsechestnut, Aesculus turbinata Bl. Red Buckeye, Aesculus pavia L. Turkish Tree Hazel, Corylus colurna L. Ussurian Pear, Pyrus ussuriensis Maxim. Yellowwood, Cladrastis kentukea (Dum...