Q: Two years ago, after some trees were removed at the front of our house, the stump holes were filled with compost and seeded with grass. This year, along with the grass, we have tiny mushrooms that pop up in great profusion after it rains. Can we get rid of them without killing our lawn?
—Dave Williams, Springfield, MO.
A: Roger Cook replies: When you removed the stumps, you probably left behind most of the roots—and a lot of ground-up stump. That all serves as food for the network of underground fungi from which mushrooms sprout. And you probably lavished water on the new grass, didn't you? Bingo, the perfect conditions for growing a bumper crop of mushrooms.
Rather than waiting for them to disappear, which could take quite a while, do the following:
Cut back on watering and reduce fertilizer use to a minimum.
Pull up any caps as soon as they appear. That doesn't get rid of the underground fungus, but it stops spores from being released.
Core-aerate the lawn in the fall and dethatch it in the spring; both of these encourage drainage and help dry out the soil.
If none of these does the trick, dig out all the buried roots, and start over with fresh soil. Just be aware, you might be in for a lot of digging.
Q: Can I just mow down the mushrooms that crop up in abundance in my lawn after it rains?
—Alex, Bellevue, Washington
A: Roger Cook replies: Absolutely. These are just the fruiting bodies of fungi that are working in your soil. They will decompose after you mow them but probably reappear again after heavy rain.