Q: In a recent column, you said that grass clippings should be left on the lawn. Won't this lead to a thatch problem?

Thatch is a very distinct item in the lawn. It is not the gray or tan, dead leaf blades left after mowing or from grass that died over the winter. Leaving clippings on the lawn does not contribute to thatch.

Thatch is a dark cinnamon brown colored layer of grass roots and above ground stems. They are very thin, and thread-like in appearance. They need to form a half-inch thick layer before thatch is a problem. The thatch layer would look a lot like a thick layer of felt on top of the soil and under the green grass blades.

Some thatch is a part of a normal and healthy lawn. A thick layer of it is often a sign of a compacted soil that is not allowing grass roots to grow deep into the soil. If you were to cut a 3-inch cube out of the soil and the middle layer is thatch, then you should core aerate the lawn. Core aeration will help loosen up the soil, so the roots can grow where they are supposed to.

Q: Is it OK to leave the grass clippings on the lawn if chemicals to kill weeds and crabgrass have been used?

A: Leaving the lawn care chemicals on the lawn they were applied to would be better than shipping them off to your compost pile or in a bag to a municipal compost pile. There is a very slight possibility that liquid broadleaf weed control chemicals that have dried on a grass leaf blade could last for a while in a compost pile and then harm a broadleaf plant when the compost is applied to a flower bed. If the products are applied as dry granules then they are unlikely to move off the lawn when bagging.

There are a few weed control herbicides that could cause a problem if the lawn clippings are bagged and then used in a garden flower or vegetable bed. They have one of the following chemicals as an active ingredient: aminocyclopyrachlor, aminopyralid, clopyralid and picloram. These ingredients kill broadleaved plants. They breakdown within a month when exposed to heat, oxygen, microbes, moisture and sunlight. If the grass clippings are piled up so that they don't have enough oxygen for bacteria to breakdown, the chemicals can last for several years. The chemicals can even be found in the manure of animals that eat treated pasture grasses. If the manure or compost is applied to a flowerbed or vegetable garden with enough residual chemical still intact, plant damage can occur.

Question: When should I take the hummingbird feeder down in the fall?

Answer: Do not take the feeder down until it has been a couple of weeks since you last saw it being used. In cold climate areas, a frost will kill off the remaining flowers. When that happens, there may be a few hummingbirds that still need a little more energy before heading farther south. They cannot get the sugars from the dead flowers, so your feeder will help.

Having a feeder up will not entice hummingbirds to stay past the time they should leave. The instinct to migrate is too strong for that to happen. If you live along the Gulf Coast, in southern California or the desert southwest, it is possible to have hummingbirds visit your yard all year long.

Email questions to Jeff Rugg at info@greenerview.com. To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.