We all are mourning the loss of so many mature elms to Dutch Elm Disease this year. Perhaps we can think of the situation as an opportunity. Most of the large elms were planted in 1909 for a major festival, so they have filled the space all that time. Some new trees that will grow quickly, that are not susceptible to disease, and that will restore our lovely urban forest are in order.

The first point to consider is that the stump and as much of the root ball as possible should be removed or ground out. There will be considerable settling for some time, especially for a large, old tree. Any new tree should be planted at least 10’ away from where an elm was removed, and the soil should have lots of compost added to make up for the nutrients used by the elm.

When replacing a tree, it is wise to consider more than just the growth rate. Is this tree known to develop surface roots? Is there room at the site for both the roots and the canopy? Is an 80’ tree really necessary?

Larger trees that are not elms are many. If you are replacing a tree from the boulevard, be sure to check with your city forester to see which varieties are permitted.

Choose among the following

Some new varieties of Elm (see below) are resistant to the disease, and can be planted as replacements.

The other varieties best suited are:
River Birch 40’-60’ - dappled shade, moist soils
Catalpa 40’-60’ - tolerates many sites, short-lived but spectacular
Kentucky Coffee Tree 50’-60’ - native, good golden fall color
Ginkgo 40’-60’ - tolerant of many harsh situations, golden leaves drop in 12 hours in fall
Hackberry 50’-75’ - native, tolerant of harsh sites, source of food for many butterflies, needs careful pruning when young
Honeylocust 30’-50’ - tolerates salt and drought
American or Mongolian Linden (if you can get well away from the elm roots), 30’-60’
Oak ‘Crimson Spire’, ‘Heritage’, ‘Regal Prince’ - each is a cross with Quercus rober, the English Oak, 45’-80’, narrower, in general, than our native oaks, and they grow faster, as well
Yellowwood 25’-40’ - fragrant flowers, moist, well-drained soil

Or perhaps look at some of the smaller trees with flowers, fruit for the birds, or great color in fall, such as Buckeye, Amur Cherry, Japanese Tree Lilac, Maackia, Showy Mountain Ash, Prairie Gem pear, Serviceberry, Sour Gum, Pagoda or Grey Dogwood, or Viburnum lentago.

New Elms
Several research groups have been working to develop elms resistant to Dutch Elm Disease (DED). There has been some success. What follows is a much abbreviated adaptation of an article out of Iowa State University.
American Elm cultivars
   Valley Forge - best DED tolerance; upright arching, vase-shaped form 26’ after 12 growing seasons, Zone 5
   New Harmony - not as resistant as Valley Forge, good shape 66’tall and 72’ wide Zone 4
   Independence - good shape, DED tolerant, “quite susceptible to elm yellows (a relatively rare disease in the Midwest)”

None of these are immune to DED and there are no mature trees yet to evaluate.

Asian/European contributions
   Accolade - good form, good resistance to DED, elm leaf beetle, leaf miner less tolerant of urban and clay soils
   Cathedral - developed at the University of Wisconsin, good form and disease resistance, Zone 4
   Frontier - zone 5-6, pyramidal form, leaves first red, then yellow-green, then purple
   Homestead - zone 5-6, pyramidal, susceptible to elm leaf beetle
   New Horizon - high resistance to disease, upright form, dense crown, Zone 4
   Patriot - high disease resistance, good shape, considered Zone 4
   Pioneer - vigorous, very broad crown, Zone 5-8
   Prospector - vase-shaped becoming pendulous. Zone 4-7
   Regal - upright oval crown, no fall color, sparse leaves (lighter shade) mean turf does better under this one, Zone 4

In each case, these trees are not identical to the glorious vase-shaped American elm. The moral for all of us who love it, is that perhaps we loved it a bit too much, and planted it so regularly that we left it no escape once disease entered the picture.