We revisit Mary Robson's drain-field garden to see how it's growing

As a teenager in Ohio, I mowed the lawn, a sweeping swath of green that met the septic drain field, where the grass was indeed greener and the ground squished under the mower wheels. My parents didn't think of eliminating the lawn or planting natives. But for some country dwellers now, the largest open space on the property might be the septic drain field. Even if your home is on city services, you might have areas where you're attempting to tame the weeds and create new plant colonies. So here's what I've done and how it's working.

In the second year of planting on my drain field, I've gone from removing the introduced Himalayan blackberries (Rubus armeniacus) and Scots broom (Cytisus scoparius) to selecting new plants. "Removed" isn't the right term. I'm still battling both of these weeds, but their presence has lightened. After brush-hogging them down (with help), digging them out and spreading several layers of cardboard and mulch two summers ago, they venture up but are being crowded out by other plants.

Keep patrolling for seedlings, which emerge constantly even after you've removed their parent plants. Look especially for the seedlings of Scots broom, which unfortunately resemble desirable native lupine when they first emerge because they're in the same legume family. Scots broom seedlings grow very fast, producing 6-inch roots and 3-inch plants within weeks of germinating in early May. Their stems feel woody rather than soft, as does the flowering lupine. Don't toss woody weed seedlings on top of a compost pile in rainy weather; they often simply regrow.

	GARY SETTLE / SPECIAL TO THE SEATTLE TIMES Elijah Blue (Festuca glauca)

Choose non-woody plants to keep roots out of drainage areas. Septic drain fields can be planted as lawn, but more ideal is Eco-turf, a mixture of adapted grasses and broadleaf plants such as yarrow.

I've chosen to plant a variety of ornamental grasses for texture and leaf interest, having learned about their value on drain fields from Sue Thompson of Harstine Heirloom Nursery, where she specializes in grasses. I've planted short blue fescue (Festuca glauca), only 12 inches tall and distinctly blue year-round. It stays in clumps: look for cultivars 'Elijah Blue,' the clearest blue color; 'Boulder Blue,' long-lived locally; and 'Sea Urchin,' which looks just as the name sounds. All of these are good ground-cover grasses on or off the drain field.

Other grasses I've chosen are blue oat grass (Helictotrichon sempervirens), with nearly "everblue" foliage through winter and late spring flowers. On the edges I've used feather reed grass (Calamagrostis x acutiflora) cultivar 'Karl Foerster' and a related cultivar, 'Overdam.' These grow to about 5 feet with plumy seed stalks.

Mow drain-field grasses when they brown out in late summer if your home needs wildfire protection. The "meadow" look speaks of summer, but the lack of water as autumn approaches makes a standing hay-like field a potential hazard.

	GARY SETTLE / SPECIAL TO THE SEATTLE TIMES Moor grass

Add color. Here comes fun. One effective drain-field planting uses lots of small native flowers: evergreen violet (Viola sempervirens), woodland strawberry (Fragaria vesca), bleeding heart (Dicentra formosa) and tiger lilies (Lilium Columbiana). Others that settle in well, though not native, are common thrift (Armeria maritima), with bright pink flowers, and tall sedum (Sedum sempervirens).

Plant spring bulbs, especially narcissus. Narcissus (daffodils, or jonquils to Southerners) bloom early above the grasses and disappear in summer as the grasses grow taller. I'm looking for the longest-lasting, those that stay in bloom for weeks, such as 'Quail,' 'Pipit,' 'Jenny' and 'February Gold.'

You'll be weeding, as ever in gardens (be sure to mulch), and the drain field will perk away, contributing essential service, while you gaze at the beauty around it.

Mary Robson is area horticulture agent for Washington State University/King County Cooperative Extension. Her e-mail is gardeningtips@seattletimes.com. For last year's story on "The taming of a drain field," go online to www.seattletimes.com/gardening.