A few times each year I get the question of what to plant over septic leach field.

My answer is always as little as possible except for grass.

Roots from plants may clog or disrupt the pipes and seriously damage the drainage field. With the easy answer said, let’s look at the dos and don’ts of planting near a septic leach field.

Herbaceous, shallow-rooted plants such as flowering perennials and annuals, turfgrass and many ground covers are unlikely to damage the lines. Don’t be too enthusiastic in tilling the soil when planting.

This is one situation where deep digging is definitely out. Also, always wear gloves when planting, weeding or doing other gardening activities that involve contact with the soil over your drain field.

This will protect you from direct contact with any harmful organisms that may be present in the soil.

Trees and shrubs are much riskier choices for the drainage field than herbaceous plants.

The woody roots of these plants are more likely to clog and damage drain lines.  Especially notorious for line clogging are water-loving trees, such as willows and poplars. 

Do not plant these near a leach field unless you are prepared financially for the possibility of needing to install a new field sometime in the future. If you insist on growing them near a field, at least plant at the far end, where the lines will be drier and less conducive to root growth.

Some smaller and less-aggressive woody species may be suitable for planting near the drain field. Some possibilities include fibrous rooted shrubs such as boxwood or holly. When planting shrubs in a leach field, place them between the lines when possible. Normally, drainage trenches are 3 feet wide with 6 feet between trenches. However, drainage spacing is not always the case.

You may contact the local health department for a map of your septic tank location.

As stated at the beginning of this article, the best answer is plant only grass over, or even near, a septic field; to do other wise could be costly in the future.

Clark Beusse is the Dawson County Extension Agent.