It's that time of year when the leaves start to turn color and fall from the trees.

What can you do about all those leaves? More than a quarter of American gardeners use a mower or grinder to take care of their lawn leaves.

With more and more gardeners using mulching mowers, it's a fairly simple thing to return moderate amounts of leaves to the lawn.

Fast facts

--What: Fall composting workshop. Learn about composting and composting with worms, and get a free composting bin and book.

--When: 9:30 a.m. to noon Oct. 14

--Where: Mid-Columbia Library, Kennewick Branch, 1620 S. Union St.

--Registration: The workshop is free but you must pre-register by calling 942-7730.

You simply mow over the lawn where the leaves are located and the mulching mower chops the leaves into little pieces and these little pieces drop down between the blades of grass. Voil ... the leaves are gone. A second pass over the lawn is even more effective in making the leaves "disappear" and providing a well-groomed appearance. It certainly bypasses the tedious step of raking and disposing of them.

If you have lots of leaves or if you don't have a mulching mower, this may not work well for you. However if you work from the outer edge of the lawn inwards, you can still "mow" the leaves into a pile in the center. This still saves you the tiresome task of raking the entire lawn.

Here are a few hints on using a mulching mower. First, don't wait until all the leaves have fallen. This could overwork a mower. Mow several times during the fall. Mow when the leaves are dry and keep your mower blade sharp. It's also a good idea to check and clean the mower filters often.

Besides mowing, gardeners can deal with leaves by sending them to a landfill or a city recycling facility. Some gardeners also compost their leaves.

Composting is a great way to handle volumes of yard waste. Compost, the end product of the composting process, is an excellent source of organic matter to use for improving local garden soils. To compost fall leaves, all you need is a little space, a way of containing the pile, a source of nitrogen, and some water.

Composting is just a process where gardeners can speed up the natural process of decay by mixing leaves and other plant waste together with some moisture. If you'd like to learn how to compost and receive a free composting bin, plan on attending a composting workshop next Saturday.

Compost or not?

-- Pine needles: Many gardening references note that pine needles should not be composted because they will make the soil too acidic. We don't really have to worry about that in our region because our soils are alkaline. However, pine needles do not break down quickly even if chopped up or shredded before composting. Use them as a mulch in areas with tender perennials that need to be covered or as a permanent mulch.

-- Sycamore leaves: Sycamore trees produce lots of large leaves. These may be a problem because of their volume, but they're fine to use in a compost pile. Keep in mind that you can reduce the volume by shredding them or mowing and raking them afterwards.

-- Oak leaves: These leaves are high in tannins and don't break down as readily as some other types of leaves, but there is no problem in composting them.

-- Black walnut leaves: Black walnuts contain a plant compound called juglone. Juglone is toxic to other plants and composting sources disagree on whether it's safe to compost the leaves and hulls. University sources indicate that it's safe to add leaves and hulls to a compost pile if it's an active pile that heats up well. They advise that it would be best to compost these materials for several months before using the compost in the garden. Apparently, the decay process breaks down the juglone, although they recommend not composting any more black walnut leaves than one-third of the pile's volume, as well as no large volumes of hulls. To err on the side of caution, it might be best to leave the hulls out.

* Marianne C. Ophardt is a horticulturist for the Washington State University Cooperative Extension Office in Benton County.