Planting on your septic bed

The best species to plant over your septic

By Lorraine JohnsonLorraine Johnson

Septic garden

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The proviso is “to keep the septic bed clear of trees, shrubs, and plants with deep roots,” says Jacki Kennedy-Ciphery of Water’s Edge Landscaping in Port Carling, Ont. “You need species that won’t interfere with the functioning of the septic system.” Kennedy-Ciphery sees lots of blackberries and raspberries growing over septics in cottage country, and points to these fast-growing, invasive shrubs as particular “no-nos.” Instead, she suggests wild strawberries, which have shallow roots and will cover the ground quickly, and clover, a hardy non-native that bounces back from foot traffic and improves the soil. “Native grasses are also good,” she adds, “such as Canada wild rye, prairie dropseed, side-oats grama and, especially, little bluestem, which you can seed and then leave alone – you don’t need to mow it unless you want a play area for kids.”

Rick Wright of Brackenrig Landscaping in Port Carling, Ont., often plants septic fields with a mix of wildflowers and native ferns, such as lady fern and New York fern. “The flowers will naturalize and the ferns don’t have deep roots, so they won’t interfere with the septic system.” He warns, however, that woody shrubs from surrounding natural areas, like viburnum and dogwood, will seed into the septic bed, and “you should cut those down, so the woody brush doesn’t get established.”

As for wildflower species that will thrive over septic beds but not cause problems, Ken Parker of Sweet Grass Gardens in Hagersville, Ont., likes Canada anemone, pussytoes, New England aster, wild bergamot, pale purple coneflower, black-eyed Susan, and both grey and stiff goldenrod, all of which “have shallow roots and can get the moisture and nutrients they need in the top few inches of the soil. And they cover the ground well.”

Wildflower Farm, a native plant nursery and natural landscaping company in Schomberg, Ont., has developed a “Septic Bed Meadow Mix” for seeding directly into sand and gravel backfill over septic systems. The mix includes tough, attractive native species such as wild columbine, sky blue aster, pale purple coneflower, and foxglove beardtongue.

For cottagers who are intent on at least a portion of lawn for outdoor activities, it makes sense to use the septic field for this. Wildflower Farm has developed a blend of native and non-native fescue grasses it has specially cultivated to be low maintenance (fescue species are normally fast-growing and require lots of water). Called the Eco-Lawn, it grows only to approximately 23 cm if left unmowed over the summer (but the grass blades are so fine, they fall over to about 10 cm, giving a nice soft carpet). Along with the lawn’s no-mow appeal, another cottage plus is its drought tolerance; once established, it requires no supplementary watering.

A final word of caution, though, when gardening over the septic bed. “Be careful not to cultivate the soil too deeply – about 15–20 cm,” advises Ken Parker, “and always wear a pair of gardening gloves, especially if your system is old and possibly leaking.”

Plants for Septic beds

• Barren strawberry (Waldsteinia fragarioides)

• Beardtongue (Penstemon digitalis)

• Black-eyed Susan (Rudbeckia hirta)

• Canada anemone (Anemone canadensis)

• Canada wild rye (Elymus canadensis)

• Common strawberry (Fragaria virginiana)

• Grey-headed coneflower (Ratibida pinnata)

• Grey goldenrod (Solidago nemoralis)

• Lady fern (Athyrium filix-femina)

• Little bluestem (Schizachyrium scoparium)

• New England aster (Aster novae-angliae)

• New York fern (Thelypteris noveboracensis)

• Pale purple coneflower (Echinacea pallida)

• Plantainleaf pussytoes (Antennaria plantaginifolia)

• Prairie dropseed (Sporobolus heterolepis)

• Side-oats grama (Bouteloua curtipendula)

• Sky blue aster (Aster azureus)

• Stiff goldenrod (Solidago rigida)

• Wild bergamot (Monarda fistulosa)

• Wild columbine (Aquilegia canadensis)

• White clover (Trifolium repens, non-native)

For photos of these and other plants, refer to these websites:

Ontario Wildflowers

North American Native Plant Society

This article was originally published on May 14, 2003

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