What to Plant Over Your Septic System

Amber Guetebier
Written by Amber Guetebier
Updated August 18, 2021
Woman planting flowers in garden bed
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The ground above your septic tank doesn't have to be a barren wasteland, as long as you choose your plants wisely

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 “Oh, I love how my septic system looks!” said no one ever. While a septic system is an everyday necessity for many homeowners, it doesn’t have to be an ugly empty patch on your land. With the right plants, you can turn that unsightly area into a beautiful focal point of your garden. Learn what to plant—and what not to—above your septic system and drainage field. 

A septic system is an everyday necessity for many homeowners, but it can also leave an unsightly area of your yard exposed. 

Perennials With Shallow Root Systems

When planting over your septic system or leach field, it is critical to choose plants whose root systems will not grow toward and interfere with the septic or drainage—a serious problem no homeowner wants to face. Some of the best options are: 

  • Ornamental grasses. Favorites include blue fescue (Festuca glauca), purple fountain grass (Pennisetum setaceum 'Rubrum'), and maiden hair grass (Miscanthus sinensis).

  • Showy but hardy perennials such as foxglove (Digitalis spp.), cardinal flower (Lobelia cardinalis), yarrow (Achillea millefolium), and ornamental onions (Allium spp.)

Shade-Loving Plants

If your septic tank is in a shadier part of your property, be sure to look for hardy but non-aggressive perennials that can tolerate shade, such as: 

  • Groundcovers that don’t get too aggressive like spotted dead nettle (Lamium maculatum), sweet woodruff (Galium odoratum), and creeping phlox (Phlox subulata).

  • Ornamentals, including bleeding heart (Dicentra spp.),  lilyturf (Liriope spp.), and coral bells (Heuchera sp.), especially Heuchera purpurea, which has dark purple foliage and contrasts nicely with lady’s mantle (Alchemilla vulgaris).

Plants That Smell Good

While properly installed, safe septic systems shouldn’t smell, ask any homeowner with a septic and they’ll tell you that they occasionally catch a whiff from leach fields and drainage pipes. Plants with fragrant flowers and leaves can make for a pleasant addition to your over-the-septic garden, including:

  • Groundcovers with fragrant foliage like creeping rosemary (Rosemary officinalis horizontali) and creeping thyme (Thymus spp.).

  • Scented, bushy perennials like lavender (Lavendula angustifolia or L. intermedia) and white sage (Salvia apiana).

  • Flowering vines with shallow, fibrous roots like honeysuckle (Lonicera sp.) and jasmine (Jasminum sp.).

  • Asiatic lilies (Lilium asiatica)

Small Shrubs & Very Dwarf Trees

In general, it’s best to avoid planting any kind of tree or shrub over a septic system. Even too much gravel over septic systems can cause serious issues. However, some showy ornamentals have relatively shallow root systems and don’t require you to dig too deep, either. For example: 

  • Low-maintenance, dwarf varieties of azaleas, such as the brilliant red Rhododendron ‘Robleza’ and true dwarf English boxwood (Buxus sempervirens suffruticosa).

  • Dwarf, weeping trees like weeping blue atlas cedar (Cedrus atlantica 'Glauca Pendula') and the ‘Covey’ eastern redbud (Cercis canadensis ‘Covey’).

  • For some fall color, consider dwarf Japanese maples. Acer japonicum ‘Fairy Lights’ is a stunning, showy, slow-grower that can handle most climate zones.

Plants That Like to Get Their Feet Wet

Septic areas, especially the drainage field, tend to have more standing water than other parts of a yard, so plants that can handle it a bit damp can do well there. Just be sure not to plant anything that loves water so much that it will tap roots way down into the earth, like willows (Salix). Remember, shallow roots are the key! Plant ideas include: 

  • Toad lily (Tricyrtis)

  • Stream orchid (Epipactis gigantea)

  • Bearded iris (Iris × germanica)

Can You Grow a Lawn Over a Septic Tank?

Colorful flower bed
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Growing a shorter perennial grass or lawn over a septic tank is one of the easiest ways to cover a patch of barren yard with something green and lush. Just choose your grass variety based on the light conditions: full sun, partial sun, or full shade. 

Should You Mulch Over Your Septic System?

Mulching over your septic system is fine, mainly because shallow-rooted plants do lose moisture faster than plants with deep roots, but you don’t need to mulch as heavily as you would a garden bed. 

What Not to Plant Over Your Septic System

Do not plant anything that grows fast or tall and has aggressive root systems. Avoid any kind of bamboo, blackberry or raspberry bushes, and nearly all trees, especially water-loving trees like birch, willow, and elms. 

Equally important is not to plant edible plants such as a vegetable garden. Unless you plan to use them only as ornamentals, it’s generally not considered safe (or appetizing) to eat plants grown on or near a septic system or drainage field.  

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