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DALY: Use care when planting around septic drainfields

Timothy Daly

Timothy Daly

Many homeowners in Gwinnett County have septic systems, and they frequently question what can be grown, if anything, over their septic drain field. Plant material can be beneficial in these areas by managing moisture and nutrient levels within the soil. It can also help limit activities that can compact the soil and reduce the effectiveness of the system. However, using the wrong plants can potentially harm the septic drain field and lead to costly repairs. Plants can be installed in these areas that will not be troublesome to the septic system if you follow some simple guidelines.

Certain plants by their nature have a greater potential to disturb the septic drain field systems. Shallow rooted annual and perennial herbaceous plants can be planted closer to the drain fields since they do not have invasive roots. Turfgrass can be grown over the drain field and is beneficial since it helps hold the soil in place. Trees and shrubs should be planted further away from it since they have a more extensive root systems. A good rule of thumb is to use the ultimate mature height of selected tree as the minimum planting distance from the septic drainfield.

Avoid plants with aggressive, water loving deep roots that typically thrive in wet locations and can clog or disrupt the pipes in the system. Some plants, such as willows and river birches, are known for invading septic lines. Others to avoid include magnolias, poplars, red maples, sugar maples, and elms. The extra moisture and nutrients are favorable to the growth of the roots of these plants causing the lines to become clogged. You can plant shallow root trees and shrubs, such as crabapples, dogwoods, hemlocks, hollies and arborvitae towards the drier ends of the drain lines.

Avoid the placement of groundcovers, such as English ivy or liriope, over septic drain fields. They can form thick mats and collect leaf debris preventing the soil from being able to dry out.

Locate vegetable gardens away from the septic drain fields. The vegetables, especially root vegetables, could become contaminated with disease-causing microbes. Different soil types vary in their ability to filter contaminants; however, there is no way to be absolutely certain that everything is filtered out. Additionally, frequent tilling and working of the soil could damage the lines.

Do not apply excessive amounts of mulch or soil on top of the drain field. Raised beds should not be installed over it. This can have a detrimental effect on the performance of the system by causing the soil to become compacted and by preventing soil moisture from evaporating.

By carefully choosing and placing plant material around septic drain fields, you can have an attractive landscape that is beneficial to the system. Most importantly, this can reduce the chances of costly septic line repairs.

Winter is also a good time to decide on what to plant in your yard. The Gwinnett County Extension Plant Sale has some excellent plants that are available for sale. Go to the Extension website at http://www.caes.uga.edu/extension/gwinnett/ to download the order form or call the Gwinnett County Extension office for a form to be mailed to you.

Timothy Daly is an Agricultural and Natural Resource Extension Agent with Gwinnett County. He can be contacted at 678-377-4010 or tdaly@uga.edu.