Seeding a Septic Drainage Field in the woods

Asked February 26, 2020, 4:22 AM EST

I am building a new home on a small wooded lot. My goal is to not own a lawnmower at this property. I would like some suggestions on how to manage the septic drain field. It measures approximately 100’ x 35’. It is on the west side of the house and will not be fully shaded for several years, if ever. I plan on mulching most of the other disturbed soil around the home and slowly adding native shrubs and ground covers as I become familiar with the property, it’s sunlight patterns and grade requirements.

I would like suggestions for the septic drain field, should I just mulch it? Is there a native wildflower mix you would recommend? Are there native ground covers that would be up to the task? There is some Japanese stilt grass down by the road and I’m hoping to avoid a complete take over by that. I’m trying to not introduce non-native plants.

I’m located in central Frederick County, MD.

Frederick County Maryland

1 Response

There is no research we are aware of regarding plant selection for septic drain fields, apart from advice from septic professionals to not use trees or shrubs. While lawn may be the default choice, we agree that a native perennial mix would be more attractive and provide environmental benefits. (All plants mentioned below are native to our area.)

A mix of native grasses and wildflowers can be obtained via seed supply companies (some offer pre-mixed blends of appropriate species based on habitat) or planted as young plants (called plugs). It would be useful to verify that "wildflower" mixes really do contain natives and not invasive exotic plants, as some do when provided by companies who do not specialize in natives. Below are three links to good reference lists of native plants in Maryland and the Chesapeake watershed. Some species are short-lived but re-seed well, though often only re-appear in a plant mix when there is a disturbance (in this case, probably digging, or in natural conditions, fire). Cardinal Flower (Lobelia cardinalis) is one example of a plant that follows this pattern. Initial seed-sown plantings may have a prevalence of some species that disappear over time as longer-lived species dominate, but their seed bank remains for occasions when the disturbance of their competition allows them to make a reappearance. Short-lived species are often included in seed mixes as they help colonize and area and stabilize conditions against erosion and weed seed competition while the longer-lived, slower-growing species establish themselves. Groundcovers used in such a mix will also help out-compete weeds and hold soil while the taller plants fill in.

Japanese Stiltgrass is indeed a troublesome weed; it is an annual, but re-seeds with abandon and prefers shaded woodland habitats. Deer can track the seeds around on their bodies, so keeping deer away would help prevent its spread to new areas.

While there is no specific mix to recommend - especially since plant choice will depend on site conditions as well as aesthetic preferences - we can list a few of the commonly-used meadow species (while conditions are primarily sunny, at least):

  • various grasses, such as Switchgrass (Panicum), Bluestem (Andropogon and Schizachyrium), Indiangrass (Sorghastrum nutans), and Dropseed (Sporobulus); Sedges (Carex) grow better in shadier sites
  • Beardtongue (Penstemon digitalis)
  • Mountain-mints (Pycnanthemum)
  • Milkweeds (Asclepias)
  • Beebalms (Monarda)
  • False Indigo (Baptisia)
  • Aster-family plants, like Asters, Joe-Pye Weed (Eupatorium), Blazing-Star (Liatris), Black-eyed Susan (Rudbeckia), Coneflower (Echinacea), Ironweed (Vernonia), Goldenrod (Solidago), and Cup Plant (Silphium)
  • Rattlesnake Master (Eryngium yuccifolium)
Shadier sites or edges of the planting where they may be more shade can make use of Vervain (Verbena hastata), some of the Eupatoriums, Turtlehead (Chelone), Foamflower (Tiarella), Coralbells (Heuchera), the aforementioned Sedges, Violets, and Woodland Asters (Aster divaricatus and A. cordifolius). There are even some shade-tolerant Goldenrods. River Oats (Chasmanthium latifolium) is a grass that spreads more aggressively by seed that would be good competition for Stiltgrass in partially shaded sites.