Is your septic system drainfield an eyesore? Are you unsure how to care for it?
Your drainfield represents a substantial investment. Treating it right, and protecting it from damage, can save considerable time, work, and money.
The following is taken from the brochure: Landscaping Your Drainfield [PDF].
Planting your drainfield may be different than other experiences you have had landscaping.
- It is unwise to work the soil, which means no rototilling. Parts of the system may be only six inches under the surface. Adding two to three inches of topsoil to the drainfield should be fine, but more could be a problem (too much can prohibit the exchange of air and water).
- Any plants should be relatively low in maintenance and water needs. Select plants that once established will not require routine watering.
Acceptable Plants for Some Drainfields
The following shallow-rooted plants can be grown on standard drainfields or mounds. Broken down by the amount of
sunlight needed, they include groundcovers, ferns, ornamental grasses, and wildflowers.
Deep Shade (receives no direct sun)
- Carpet Bugle (Ajuga reptans): an aggressive groundcover with blue flowers in the spring
- Japanese Spurge (Pachysandra terminalis): an aggressive evergreen groundcover; once established, it forms a thick cover, minimizing weeds
- Periwinkle (Vinca minor): an evergreen groundcover with periwinkle blue flowers in the spring. Moderately drought tolerant in shady areas
- Sword Fern (Polystichum munitum): a native evergreen fern that in a shady location is very tolerant of our dry summer months — easy to grow
- Irish Moss (Sagina): not a true moss, but a good look-alike and much easier to grow — does best when mixed with ferns and other plants
Partial Shade (receives about 4 hours of sun)
- Blue Star Creeper: an attractive, fast-growing groundcover with tiny blue flowers
- Carpet Bugle and Sword Fern (see above): also suitable, but the fern will not be as drought tolerant as in the shade
- Creeping Rubus (Rubus pentalobus): species of ornamental bramble, but its leaves and small flowers are much more decorative than its thorny cousins — the rooting carpet of stems can easily grow four feet a year
- Vaccinium "Well's Delight" (Vaccinium crassifolium): shiny, dark evergreen leaves with dainty pinkish flowers — a good, three-inch-tall groundcover for partial sun
Full Sun (receives sun all day or about 8 hours)
- Kinnikinnick (Arctostaphylos uva-ursi): a native evergreen groundcover known for its drought tolerance once established. Requires a well-drained soil; not tolerant of wet areas.
- Blue-Silver Fescue (Festuca cinema): an ornamental grass with blue-silver blades. A short, clumping grass requiring a well-drained soil, not drought tolerant.
- Blue Oat Grass (Helictotrichon sempervirens): an ornamental grass with stiff evergreen blue blades. Requires well-drained soil.
- Fountain Grass (Pennisetum alopercuroides): an attractive fountain grass with arching stems bearing soft, bottlebrush clusters of fuzzy flowers. Grows to about 1 1/2 to 2 feet and is tolerant of moist soils, unlike some other ornamental grasses.
- Vaccinium "Well's Delight" and Creeping Rubus, noted above, are also suitable.
A meadow with a mix of native grasses and shallow-rooting flowers can be very attractive, and good for wildlife, too.
The use of wildflowers with bulbs is an easy way to landscape the drainfield and have two to three seasons of
color. Daffodil and crocus bulbs are easy to naturalize and both are reasonably drought tolerant and will return year
after year. When selecting wildflower seed, there are several important considerations:
- Be sure the seed is viable and not left over from the previous year. Many mixes currently available may not be well suited for our Northwest climate.
- As with the Acceptable Plants above, seed selection must be based on the amount of sun. There are a variety of native seed mixes for all types of sun-shade situations.
- The seed mix needs to be a blend of annual and perennial seeds. Avoid wildflower seeds that contain knapweed, hawkweed, or other
noxious weeds. Packets of wildflowers from out of
state may contain weeds considered a nuisance here in Washington. Look for Washington state labeled packages that say "no noxious weeds" or "no detectable weeds."
- If your drainfield currently has grass, you cannot just spread the seed over the grass and expect it to grow. Remove the grass in small areas, six inches or so in diameter, and sow the seed in those areas. The grass needs to be kept out of the area until the seed has germinated and is large enough to compete with the grass.
- May is generally the best month to sow wildflower seeds, when we still get enough rain to keep the seeds moist during germination. If we have a dry month, sprinkle the seeds with water twice a week.
Talk to your septic system designer or installer for more answers to your questions, or call Thurston County
Environmental Health's Septic Helpline at 360-867-2669. The TDD line for the hearing impaired is 360-867-2603.