Frequent, heavy rains are the "potion" that make large, colorful mushrooms appear almost magically in home landscapes.

"Unless you're an expert, I wouldn't advise eating any of them. Mushrooms can be poisonous to humans," said Ward Upham, horticulturist with Kansas State University Research and Extension. "But, unless the mushrooms are growing in your lawn in an arc or circular pattern - called a fairy ring - they're likely to be fairly harmless to plants. In fact, some can be beneficial in the landscape."

These non-ring-forming mushrooms can be mycorrhizal, which means they live in a two-way, beneficial relationship with tree roots. Or, they can be saprophytic, living on such dead organic matter as wood chips in the soil.

Still, they may be a nuisance. Or, they may be a concern in a children's play area.

If so, the best way to control such mushrooms is simply to pick and dispose of them as soon as they appear. A follow-up step is to remove any large organic debris from the soil, Upham said.

"A mushroom is just the fruiting structure of a fungus. Spraying it with fungicide does little good because most of the parent fungus is inaccessible under ground," the horticulturist explained.

Many types of mushroom will go away as soil dries

"That's why patience can be another good approach to mushroom management," Upham said.

Fairy-ring mushrooms are much more difficult to control and can kill lawn turf, he said. This type of mushroom forms a dense mat of interwoven filaments that makes organic matter decompose. This process, in turn, releases nitrate - a fertilizer. And the nitrate stimulates the turf on the outside of the ring, forming a margin of dark green grass.

The fungal mat itself won't allow water to get to grass roots. Plus, the fungus sometimes releases a byproduct that's toxic to turf. So, the result often is a dead or dying yellow-brown center for the dark green "ring."

"There's really no best solution for this problem," Upham said.

The current treatment options include:

* Hire a lawn-care company and get the fairy ring drenched (sometimes repeatedly) with a commercial fungicide such as Prostar or Heritage. In some cases, that will reduce the symptoms.

* Dig a 1-foot-wide trench that is 6 to 12 inches deep on both the inner and outer sides of the ring. Remove the trenches' soil, and replace it with soil that's not infested with the fungus. Sometimes this will eliminate a ring.

* Mask the symptoms by fertilizing the rest of the lawn so that it's as dark green as the ring.

"Be warned, though, that applying fertilizer this way will tend to promote other problems in what now are the healthier areas of your lawn," Upham said.