February 4, 2016 – Kenosha News
This is the third of a series of columns on large (over 30 feet tall) tree species that could be planted as replacements for dead ash and other shade trees.
Many lindens, with their heart-shaped leaves, are good urban shade and street trees. Lindens are a pollinator plant because bees love the small yellowish-white flowers with light green bracts that appear in mid-summer.
Basswood or American linden is a Wisconsin native. It is valuable in the natural landscape but not suited to urban sites. The species tends to produce a multitude of suckers. Cultivars are less likely to sucker.
Littleleaf linden has a formal pyramidal form. It has small (1 ½ to 3 inch) leaves and flowers. Autumn color is yellow. Narrow branching angles can be a problem so choose cultivars with good branching structure and a strong central leader.
Silver linden features three to five inch dark green leaves with silvery undersides. The fuzzy leaves discourage Japanese beetle feeding, which can be a problem with other lindens. Bark is light silver grey. Young silver lindens are pyramidal, which widen with age. They have a good branching structure.
Other good choices for lindens are the hybrid trees ‘Redmond’ and ‘Harvest Gold’.
Once one of our major shade trees, large stately elms are now scarce because of Dutch elm disease. Native elms persist in native landscapes and fencerows, but often die of disease by middle age.
Extensive evaluation and breeding programs at botanical research institutions have produced a number of new disease resistant elms. These new hybrid trees are vigorous and good for urban areas. Valley Forge, New Harmony and American Liberty are selections of American elm with good disease resistance. Elm hybrids (e.g. Frontier from U.S. Arboretum, and Accolade and Triumph from Morton Arboretum) are attractive and Dutch Elm disease resistant. Because a number of new elm cultivars are appearing on the market, make sure to carefully investigate the choices before making a decision.
Lacebark elm is an excellent shade tree with beautiful mottled gray, green, orange, and brown pealing bark. In autumn the leaves are yellow to reddish-purple. It is very tolerant of urban soils.
For lists of recommended replacement trees and last week’s column on maples, please visit: Gardening Questions.
Barb Larson is horticulture educator for the Kenosha County University of Wisconsin Extension. She holds a master’s of science in horticulture from the University of Wisconsin-Madison. If you have a plant or gardening question, email her at email@example.com or call 262-857-1942.