Organic Weed Control - U of I Extension

News Release

Organic Weed Control

This article was originally published on October 30, 2008 and expired on January 30, 2009. It is provided here for archival purposes and may contain dated information.

University of Illinois
Master Gardener

By Michelle M. Follett
Ogle County
Master Gardener Intern

Being organic takes effort, especially in weed control. Being so, in rocky conditions such as a gravel driveway, takes even more. In these conditions no matter how masterful the weed puller that tap root is not coming up! To keep weeds away until winter comes to finish the job, I loaded up with as many weeding options as I could find. One unexpected source for ideas was the National Audubon Society. In its Healthier Choices pamphlet, the organization suggests a couple of options, and I put them (plus one of my own) to an informal evaluation.

First in the evaluation was boiling water. My first thought was probably similar to yours: It may be organic but wasteful to use a non-renewable resource. My informal testing proved this to be the case. Boiling water was effective on only the youngest sod grass growing in cement cracks. Every other weed and every other condition showed limited signs of distress 48 hours after application. It also lost points on the instant gratification factor: a watched pot never boils!

The next method was propane. You can purchase a small, hand-held tank at most hardware stores. The cost was almost the same as the popular gallon-sized concentrated herbicides – although the refill tanks are less expensive. I noticed again that the chemical alternative is a limited resource, but I couldn't curb my enthusiasm to play with fire! Fire is the biggest concern to this choice: The propane torch should not be used near the lawn and children and pets should be kept away. Danger aside, the propane torch proved more effective than the water. It effectively killed tender dandelions but once the dandelions had flower heads the propane lost its effectiveness. It burned isolated clover and grasses spectacularly, but larger stands did survive the treatment.

When I saw that the propane was more effective than the boiling water, I considered other ways to burn plants. A heat gun looks like a standard hair dryer but would set hair afire if attempted that way. It is available in most hardware stores and similar in cost to herbicides. Its advantage is that it can be re-used with little cost. It has the same dangers as propane but also the plants can burst into flames when exposed to the gun too long – that discovery curbed my enthusiasm! While the heat gun was even more effective than the propane, having it tethered to an extension cord limited my use of it. Out of the three, the heat gun killed the most species of weeds. Only the biggest (healthiest) weeds that were in full bloom managed to survive – but a second session killed the last of them.

In the end, I learned that performing scientific experiments on aggressive, invasive weeds should be performed in some else's driveway – I'll be spending next season killing off the extra weeds I let grow for the sake of finding organic alternatives.

Pull date: January 30, 2009