Growing Concerns 576: Ash replacements, clover in lawn


Ask the experts which tree to pick for one that's garden-friendly


Dear Janet,

We're trying to get the best new trees we can to replace four ash trees we lost to emerald ash borer. We liked those trees but they were tough to garden under. They had lots of surface roots. What's the best tree for optimists who are looking forward to new trees with new gardens under them? - L.J. -

Dear L.J.,

The best judge of that is someone who's gardened under many different trees, in lots of situations. Since there are so many tree species, it would take more than a lifetime to compare them all. So we called friends with broad, long experience to ask which Michigan hardy tree they would nominate for the honor. Each one qualified their response with something on the order of, "Only one?! Okay, if I have to choose just one tree to garden under.."

Ginkgo is our own favorite, for its deep roots and high shade. Hickory would be our number one, but some autumns the falling nuts are downright dangerous.

Allan Armitage, author of the book we can't do without, Herbaceous Perennial Plants likes gardening under dogwood and adds, "pecan is the worst."

David Michener, world traveler and assistant curator at University of Michigan's Matthaei Botanical Garden, likes Kentucky coffee tree (Gymnocladus dioicus) for deep roots, light shade and because it's in the pea family so it adds nitrogen to the soil.

Roger Swain, formerly of PBS' Victory Garden and now with the new program "People, Places and Plants," votes for a peach. "Fruit trees need good ground... or they never bear well, so I say plant them right in the perennial border." He says that the show of the moment under his peach tree is blue bearded irises and ox-eye daisies, blooming later than the ones out in the open.

Ann Hancock, likes mature white pines overhead. They're open and airy, don't present much root competition and, "they're self-mulching!"

Claire Dusak, horticulturist at Phipps Conservatory in Pittsburgh says, "It has to be a Stewartia pseudo camellia, what a tree! The one I grow under is single stemmed -- you couldn't do much under the low shrubby ones. I didn't actually plant under it but things seeded themselves under there and moved in, and it's so gorgeous."

Alan Barnhagen, director and horticulturist at Powell Botanical Gardens outside Kansas City, first ruled out all the maples and lindens, then settled on Kentucky coffee tree. When I told him it was already on the list he said, "Oh   good, then my number two is yellowwood (Cladrastis lutea), another legume to enrich the soil!"

Chuck Martin, curator of woody plants at Dow Gardens in Midland, Michigan, says the biggest thing is to be under a tree that doesn't give you much root competition. He votes for the swamp white oak (Quercus bicolor).

In the Wake of Emerald Ash Borer: Ash tree replacements

As the non-native insect, emerald ash borer (EAB), continues killing billions of ash trees (Fraxinus species) throughout eastern North America, there is as yet (2014)  little we can do to stop it. Here is a list of trees suitable for replacing an ash at streetside or in your yard. It was compiled from the choices offered by city foresters in our area, at the epicenter of the emerald ash borer plague.
On our list we have included detailed descriptions of the trees. For more about emerald ash borer, search those words here on our site and visit the U.S. Forestry Service  EAB information page where you can learn about EAB status in your area, and the latest on its control.
download the ash tree replacement list in pdf



Dear Janet,

I've developed a bad case of clover in my lawn this year. Can anyone tell me what to use to get rid of it and when? - C.B. -

Dear C.B.,

To knock down clover in one application, pick a weedkiller with the active ingredient dicamba. Others, such as 2, 4-D may have to be applied several times.

Dale White, prescribes organic and conventional lawn care products to customers every day and hears back from them which gave the most success. "Dicamba is always in a concentrate, not granules," he says. "Weed B® Gon Chickweed and Clover Killer is one that will work."

"Your reader should be aware," White continued, "that when clover takes over it may indicate a nitrogen deficiency, where clover can grow better than the lawn can, so it does. Many people want to use only organic things on their lawn and that's good, but you can't just stop everything including the fertilizer."

Short reports

Clover in the lawn? Maybe you should hold off on that weedkiller.

Prior to the invention of herbicides that can kill broadleaf plants while leaving grass pretty much alone, every package of grass seed came with clover in it. Clover, a pea family plant or "legume," fixes nitrogen from the air, helping the grass grow. Every bit of clover leaf that falls from a mower breaks down to give up "free" nitrogen that the lawn could not otherwise have gotten. Thus when herbicides became available, many groundskeepers refused them since, "they'll kill my clover." Gradually, herbicide marketers won out and clover began to be considered a weed.


Green thumbs up

to the monarch butterflies now in our yard. Sorry, guys, that development eliminated almost all the milkweed hereabouts. I promise to keep my patch going for you and to guard it from any sprays that would taint the nectar and kill your caterpillars.


Green thumbs down

to waiting until fall if you find just the right plant now. The shopper we overheard  said, "I'll buy it later" about an 'Onondaga' viburnum, will likely be out of luck in fall. Its pretty fruit will ripen in August to catch another buyer's eye.

Originally published 7/24/04