Pros and Cons of Septic Drain Field Plantings

What can I plant over a septic system leach field? This is a common question from gardeners, and one that deserves a lot of attention. A publication from the Virginia Extension system provides the most entertaining answer: “Something fragrant.”

Seriously, great care should be exercised when planting near a septic system. The challenge of leach field gardening is to find plants that will meet your landscaping needs without clogging the drain pipes. Following are some typical questions that we receive on this subject.

17.Why plant anything?

1. There are many reasons. Plants can help the septic drain system to function best by removing moisture and nutrients from the soil. Plant cover helps to reduce soil erosion. At a minimum, the leach field should be planted with a cover of grass. Also, many homeowners have limited space and this area might be the only place that flowers and other ornamental plants can be grown.

17.What plants are safest to use over or near a drain field?

1. Shallow rooted herbaceous annuals and perennials, turfgrass and ground covers are unlikely to damage the lines. For obvious reasons, avoid deep tilling or digging when preparing the soil. Always wear protective gloves when working with the soil over a drain field.

17.How about planting trees and shrubs in or near the drain field?

1. Trees and shrubs are more risky choices than the herbaceous plants. The woody roots of these plants are more likely to clog and damage the lines. The water loving trees such as willows, poplars, birches and maples are notorious for seeking out and filling perforated drain pipes with roots.

Some of the less aggressive and smaller growing woody species

may be suitable for planting near a drain field. Some possibilities include

crabapples, dogwoods, pines and sourwood.

Q. So, how far away must a tree be located so that it can’t possibly clog drain

lines?

A. An exact distance for each tree species is not known. Given the fact that

the average root spread of oaks and some other species is approximately

3 times the canopy spread, stay as far away from drain lines as is

feasible.

Tips for Reducing Drain Clogging By Tree Roots

_Select less aggressive species.

_Plant large growing trees as far as possible from the drain field.

_Prepare the soil before planting trees by loosening the soil and breaking through subsurface compacted areas. Growing roots follow the path of least resistance, penetrating less compacted cracks or paths as they find them. If the first soft path that they encounter happens to be a drain field, that is where they will proliferate.

_Consider the use of a commercial root barrier. Although somewhat expensive, this technique may be worth trying. One method involves the use of a geotextile that has been impregnated with a long-lasting herbicide. A sheet of this material is placed vertically in a trench from the soil surface to a depth of 2 to 3 feet. It has been used successfully to restrict root growth in street tree plantings. The manufacturer’s instructions must be followed closely when installing root barriers.

Question of the Week: I have found what looks like cocoons hanging from the branches of my junipers. What is this? Will they damage my plants.

Answer: These are bagworms. They are currently infesting many cedars, junipers, arborvitaes and Leyland cypress trees. These are unusual insects in that they spin a case or cocoon and carry it with them as they feed.