Weeds and fairy rings

By John Fulton

[March 23, 2011]  What's that weed?

Each year, the winter annual weeds chickweed and henbit run No. 1 and 2 in the early spring. Winter annual weeds can actually germinate in the fall, carry through the winter, then get going very early in the spring. They also are done by the heat of the summer, leaving seed to germinate again later in the fall.

Right now chickweed stands out in yards because it is quite abundant and has a lighter green color than grass and most other weeds. It is even evident as grass is just beginning to green up. There are two types: common chickweed and mouse-ear chickweed. Henbit is easier to identify since it has purple flowers and smells like mint.

As for control, that gets a bit easier. The straight 2,4-D that is used on dandelions seems to act like a fertilizer for chickweed and other problem weeds. It's a growth regulator, and if it doesn't actually kill a weed, it does make it grow faster. Combinations that contain 2,4-D, MCPP and dicamba are rated very effective on chickweed, henbit, red sorrel, purslane, white clover and others.

These combinations are sold under several different trade names. You can find these at most hardware, discount, and lawn and garden stores. Just check the label under active ingredients and check for two long chemical names and dicamba. You can also check to see that it says it will control chickweed and henbit.

Just remember the control time for most broadleaf weeds is early May. This group of chemicals is effective in the 50-degree range and up. It just takes a lot longer for control with very cool temperatures.

As with any chemical control, read and follow label instructions very carefully. These product labels will have some cautions you should be aware of concerning injury to sensitive plants. This is because dicamba can drift as a vapor for a few weeks after you apply it if the weather gets hot and sunny.

Fairy rings, mushrooms and puffballs

Throughout the year I get several calls and samples brought in dealing with puffballs or toadstools. Even this early in the season, we have had calls about dark green grass in rings that kind of look like a target pattern. These rings are called fairy rings, and they frequently have puffballs or toadstools growing in the area.

Fairy rings are caused by a fungus in the soil. Actually there are about 50 fungi that can cause fairy rings. These fungi feed on decaying organic matter such as large roots from trees that were in the area, or from buried lumber. The dark green circle part of the equation comes from extra nitrogen that becomes available as the organic matter is broken down by the fungus.

Some prevention will help keep the problem from occurring. Simply removing stumps, large roots and not burying lumber help prevent this type of problem.

As for a cure, fungicide drenches have been successful on a very limited basis. One option is to mask the symptoms of the dark rings by fertilizing the surrounding grass with a high-nitrogen fertilizer to make that grass green also.

As for the puffballs, toadstools or mushrooms, they are part of the same complex as fairy rings. They are part of the natural decay process that helps break down large wood items in the ground. There is no real control, so mowing them off or knocking them loose with a garden rake is about the best thing going.

[By JOHN FULTON, University of Illinois Extension]