For many years, my property line was bordered by a small patch of aspen trees planted by a well-meaning neighbor. They were lovely for a few years but despite good care, things began to change – fungal diseases, insects and visible cankers, anemic fall color, as well as “gifts” in the form of aspen suckers peppered both lawns. While I’m not a lawn zealot, these suckers can rather quickly turn into a mini grove of trees as aspens reproduce by sending up shoots from the root of the mother tree. Suckering sometimes indicate that mom is on the decline, which in this case was true.
In early spring 2014, the owners decided the aspens were beyond saving and they removed the ten year old trees. With the trees gone, the suckers continued to sprout with a vengeance, as the remaining underground root stock tried to offer us replacement aspens.
To win this battle, before every mowing (and sometimes more often) we diligently removed the tender new shoots and their roots by hand and dabbed freshly cut larger suckers with a product recommended by our local garden center (look for active ingredient Ethyl 1 Napthaleneacetate). Ideally, we would have tackled this without chemicals, but in this case, we were advised to go this route. Additionally, we aerated the lawn and over-seeded the grass to make it healthier and thicker, hence more difficult for suckers to emerge. To discourage sucker production, we were vigilant about not over watering.
I am proud to say that this year our persistence has paid off. We’ve not had a single sneaky shoot in the lawn or adjacent garden bed, even with this year’s abundant moisture. The remaining root stock appears to have died out, so (fingers crossed) the suckers are gone for good. For more info on reducing tree suckers and seedlings: http://www.ext.colostate.edu/ptlk/1538.html
Our experience is very common. Aspens are beautiful in the mountains, but ill-suited for the urban landscape. At lower elevations they are frequently disease prone, insect plagued and short lived. Since they thrive in moist, well-drained and slightly acidic soil and at higher altitudes, the Front Range soil, which is predominately compacted, alkaline and clay, is just not ideal. If you already have aspens on your property, here is information which may help you keep them at their best: http://www.ext.colostate.edu/ptlk/1701.html
If you are thinking of adding trees to your front range landscape, check out this list of tree recommendations from Colorado State University http://www.ext.colostate.edu/pubs/garden/07418.html
Written by Linda McDonnell, a Denver County Master Gardener since 2013