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Sunday - May 29, 2011

From: Grosse Pointe Woods, MI
Region: Midwest
Topic: Shade Tolerant, Trees
Title: What will grow under neighbor's overhanging tree in Grosse Pointe Woods MI
Answered by: Barbara Medford

QUESTION:

My next door neighbor has a beautiful tree that is easily 60 years old and thus not going anywhere. Unfortunately, for me the roots of this tree have extended under a large corner of my back yard. Additionally, the leaves and branches extend over the corner also. These two factors have negated any chance of me keeping grass in the area. I was wondering if there is a ground covering you could recommend that would look nice and be able to survive the heavily shaded, root-crowded soil area. I have ground ivy in areas of the yard, but I was hoping for something that would add a little more color.

ANSWER:

You would probably wish that whoever planted that tree had asked the questions that our correspondent in this Mr. Smarty Plants previous answer did. However, as old as that tree is, there was no Internet then and, alas, no Mr. Smarty Plants to ask.

However, as you say, the tree is there, let's see how we might make the best of it.  Many trees are allelopathic, and develop self defense measures of emitting toxic substances from leaves, roots or stems (or all three) that inhibit growth beneath them. Trees generally don't develop these tendencies until they are somewhat mature, which explains why you can plant under young trees and the understory plants do okay for a few years and then start to dwindle away. And, of course, shade is a problem, too. We consider "full sun" to be 6 hours or more of sun a day, "part shade" to be 2 to 6 hours a day, and "shade" less than 2 hours a day. So, the first thing you have to consider is the light requirements of the plants you are trying to grow. Since you didn't say what tree your neighbor has, we don't know to what degree allelopathy may figure in your problem. Some trees, like members of the Juglandaceae family, including Carya texana (black hickory), Carya illinoinensis (pecan), and Juglans nigra (black walnut) are all especially aggressive in defending their turf. Most oaks are also equipped to clearing the ground under them to ensure they get all the moisture and soil nutrients they need. 

Given the choice between having great trees and having ground cover under them, we would vote for the trees every time. And it's necessary to remember that most tree roots occur in the upper 12" of soil, and may extend three times the dripline of the tree. Planting within the dripline can damage the roots of the tree, and the understory plant probably doesn't have a chance of competing anyway. The Lady Bird Johnson Wildflower Center recommends only plants native to North America and to the area in which they are being grown, as these are adapted by millions of years of experience to the soil, annual rainfall and temperatures of that area. We still can't guarantee that any plants we might suggest will flourish beneath your trees, and you may decide to simply cover the bare ground with a good quality shredded hardwood mulch. This will have to be replenished from time to time, but as it decomposes, it will add nutrients to the soil, and improve the soil texture, as well as protecting the tree roots from heat and cold. We will try to find some shade-tolerant plants that are native to your USDA Hardiness Zone of 5a. Follow the links to the webpage on each individual plant and learn more about it.

Additional color is more difficult. Color usually infers blooms, and most ornamental plants require more sun to bloom well. If you decide to give up and go the mulch route, and since you surely don't expect any blooms in your Winter, you could even put some pots of shade-loving plants under that tree, enjoy them in the warm weather, and either let them freeze and plant fresh next year, or put them in a garage or basement to hold over. It would not be necessary that they be native, because you are not trying to maintain them year-round in local soil.

We are going to go to our Recommended Species section, select Michigan on the map, and then select shade tolerant plants that we think might get along under the tree. In the right-hand sidebar on the resulting list of 156 possible plants, we will select on "herb" (herbaceous blooming plants) under General Appearance and "shade" under light requirement and see what we can find. We got 39 possibilities under "herb" and "shade." Just as an experiment, we then selected, also, height of 0 to 1 ft., which would make sense for a ground cover. That narrowed the choices down to 9, so we'll work with that, but now you know how to do your own searches and select your own specifications. Now, here's the amazing thing-ever single resulting plant of the 9 in that last search turns out to be a woodland plant that might just do very well in your situation, so we are going to list them all. This doesn't happen very often. Be sure and follow each plant link to our webpage on that plant for more information.

Woodland ground covers for Grosse Pointe Woods, MI:

Asarum canadense (Canadian wild ginger)

Cornus canadensis (Bunchberry dogwood)

Coreopsis lanceolata (Lanceleaf coreopsis)

Dicentra cucullaria (Dutchman's breeches)

Hydrophyllum virginianum (Eastern waterleaf)

Mitchella repens (Partridgeberry)

Sanguinaria canadensis (Bloodroot) 

Uvularia sessilifolia (Spreading bellwort)

Viola pedata (Birdfoot violet)

From our Native Plant Image Gallery:


Asarum canadense


Cornus canadensis


Coreopsis lanceolata


Dicentra cucullaria


Hydrophyllum virginianum


Mitchella repens


Sanguinaria canadensis


Uvularia sessilifolia


Viola pedata

 

 

 

 

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