By Megan Gross, Horticulture/Natural Resources Extension Agent, Colorado State University Cooperative Extension
I happen to know a retired couple who recently decided to create a berm along the front of their home to help buffer the wind.
In addition to the "buffering quality" the berm would provide, this well-intentioned couple also expected the berm would add to the aesthetic value of their property. This seems an obvious expectation; why else would any sane person sacrifice a trip to Burma for a pile of dirt and some seed, if not for visions of an alpine meadow just footsteps from the front door?
So, the happy couple set about building their berm. Their first step was to have dirt (note: "dirt"; not "soil") brought in from some other development site. This is a common way for people to get dirt in our area. Usually the top soil is stripped away from the site and sold or donated to Person A. Because there is still plenty of unneeded dirt at the site, Persons B through E can step up for their share of whats left. I suppose one could insist Persons B through E are indeed receiving "top soil"; after all, once the top ten feet are stripped, that eleventh foot of dirt is "on top".
Unfortunately, its this first step that usually determines whether the project will flourish or flail. While excavation dirt looks innocent enough to the naked eye, you can pretty much guarantee it contains teeny, tiny weed seeds that have been waiting for as many as twenty years to germinate. And dont think these weeds are going to wait for your native grass mix to get a jump start.
But our still happy couple doesnt recognize the potential weed problem. They proceed with seeding a low-grow, dryland grass mix with wildflowers as soon as the berm is in place (this was last September). They cover the seed with certified weed-free straw to keep it in place and irrigate to keep the top inch of soil moist. In other words, have done everything right... just about.
The following spring (this year) they noticed their berm is nothing but field pennycress, yellow clover, and thistle. My recommendation to them was to kill the weeds as soon as possible, reseed, and keep an eye out for new weed growth. Unfortunately, their first effort was a complete waste of time.
Now, dont get me wrong; excavation dirt isnt all bad. You just have to recognize that seeding right away isnt the best plan. The couple should have waited for the weeds to germinate, killed them all (with herbicide or by pulling) and then seeded their grass and wildflower mix. It might even be a good idea to wait a couple of weeks after the first weed kill and see what else comes up before sowing the seed.
While most people are attracted to the grass/wildflower mix because it is seemingly low-maintenance, such a project still requires careful planning and, yes, weed management. So, before trading berm for Burma, be certain to make decisions that will ensure you only have to make that trade once. And please call your local extension office if you have any questions.
Photograph courtesy of Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010