In Good Thyme - by Mariana Graham

Appeared in WNT, March 28, 2001

Ever since the day I wore a Master Gardener tee shirt to my fitness center, I've been fair game for gardening advice from the staff and clientele. As I attempt to tone my middle-aged muscles and work off a few zillion calories, I'm asked questions on everything from pruning roses to caring for Christmas cacti. I huff and puff my opinions and educated guesses while jogging in place or pumping the abs machine. Working out has become a sort of sweaty game of horticultural Jeopardy set to a disco beat. I rather enjoy having to think as I gracelessly fling my limbs to the beat of a Village People hit.

A couple of weeks ago a woman in a purple leotard asked me how to get moss out of her lawn. She told me she'd already mowed it twice this season, but was dismayed to see that there were lots of patches of moss where there had been grass last summer. I told her she could probably get rid of the moss, but she was going to have to stretch a few muscles to make it go away.

Mosses are primitive plants that reproduce by means of wind-borne spores. Their fine, threadlike stems and tiny leaves form a thick, velvety mat. They don't kill or crowd out lawn grasses, but they will fill in the places where grass has stopped growing. 'Got moss? That means conditions are averse to growing healthy grass, and you've got to correct them. Look at it this way: Moss likes shade and acidic, compacted soil that may have poor drainage, excessive moisture and low fertility. Grass prefers sun and neutral, friable, well draining soil that receives balanced watering and regular fertilization. If the grass isn't getting what it needs, moss may move in. It prefers to grow during the winter and is at its prime in early spring.

Let's start by removing the moss, then making the environment more grass friendly. Rent a dethatching tool or rake the lawn vigorously (there's your workout!) to remove as much dead grass and moss as you can. Use a lawn moss control product to kill out the stubborn stuff. Washington State University Cooperative Extension recommends a liquid ferrous sulfate compound. Read the labels of the various commercial compounds on the market. WSU research shows that lime and copper sulfate compounds don't work well on moss, and zinc sulfate will kill moss, but may zap your grass as well. You can then overseed with a blend of seeds specifically designed for the Pacific Northwest. Your nursery professional can help you choose the right mixture.

Once your renovated lawn is up and growing, keep it healthy throughout the growing season so moss can't get a foothold next year. If the area is too shady, consider thinning overhanging tree limbs to allow more light. Raise soil pH with an application of dolomite lime. If the soil is compacted, aerate it. Ensure that the lawn gets enough water. It should penetrate the soil to a depth of 12 to 24 inches. Long, less frequent watering rather than many short squirts with the garden hose promotes deeper, healthier root growth. Fertilize the lawn several times during the growing season. The fall fertilization is probably the most important, as it, too, promotes strong root growth.

For more in depth information on lawn maintenance, call the WSU Cooperative Extension Office in Coupeville, 679-7327 or stop by the office at 101 NE 6th Street to obtain a booklet on the subject.
If you've done all the right stuff and still have more moss than lawn, you might want to consider replacing the grass with a shade-tolerant ground cover. You can't play golf on it, but it's a heck of a lot less frustrating.

Another option is to give in to the moss. Look at it as a low-maintenance lawn that requires no mowing. If you keep it relatively moist and it doesn't get heavy foot traffic, it will stay soft and green most of the year. Once the remaining grass has been removed, you can promote moss growth by feeding it with diluted buttermilk or yogurt. You can even spread it between pavers or on decorative rockwork by mixing up some moss and buttermilk in a blender, then pouring it over the surface on which you want to grow moss. Add ferns and a few shade-loving perennials and you'll have a serene, Zen-like retreat with no mowers allowed. Oh, and don't forget to scrub out the blender!

Mariana Graham is a Master Gardener and member of Garden Writers Association of America. Contact her at Whidbey News Times, 675-6611; fax 675-2732; wnt@whidbey.net.