Explore Landscaping Options for the Septic System

Last month we talked about finishing an onsite system site for proper performance and customer satisfaction. An aspect of that discussion is addressing a common landscaping question after a system is completed: What can I plant over and around the septic system?

As the installer, you may not want to get involved with establishing vegetation, but there are some basic things a homeowner should know about planting around or over a system. Give them some guidance now and it can save both you and the homeowner headaches down the road. What follows are do’s and don’ts we’ve learned over the years about landscaping over the septic system.

TURF GRASS CHALLENGES

Well-established vegetative cover will help ensure a long-lasting operating system by reducing problems due to erosion, removing water and nutrients from the soil, providing an insulating layer and making for a more attractive yard. In the past, the accepted vegetative cover was some type of turf grass adapted to the area of country where the system is installed. Turf grasses were viewed as ideal because they have relatively fibrous root systems and seed is readily obtainable. The only choice to be made was the right mixture for sun or shade. Once established, they create a nice open area good for dogs and kids, while the root system is not going to interfere with the operation of the system.

This is still a popular option for a lot of people, but it is not without some drawbacks. Keeping turf grass in good condition requires input of herbicides, fertilizers and, most of all, water. We advise not to add extra water to burden onsite systems, so watering common turf grasses during dry periods is undesirable. More and more, installers are asked about alternatives because the homeowner does not want to have to take care of a lawn area. Or the homeowner is a gardener and wants the area covered in flowers and vegetables!

NO EDIBLES

When they ask about vegetables, the quick answer is “absolutely not!’’ Sometimes this message is not given clearly enough, but the message needs to be emphatic; growing vegetables over the soil treatment part of the system is a bad idea. There are several reasons: First, there is the opportunity — particularly with root crops like carrots or potatoes — to come directly in contact with untreated septic tank effluent containing all the associated pathogens. It is a good way to get sick.

Aside from the health risks, gardening involves constant tilling of the soil. This can lead to compaction that can negatively impact oxygen exchange to the system, reducing acceptance rates and treatment. Gardening usually also entails clearing the surface to reduce plant diseases, leaving the surface open to potential erosion and reducing the amount of vegetation needed for insulation during the cold months.

In addition, ensuring good growth in the garden requires use of pesticides, herbicides, fertilizer and, most of all, water. These operations can add excess water to the system and cause soil compaction problems.

ORNAMENTAL OPTIONS

Homeowners also ask if ornamental grasses or perennial prairie grasses and wildflowers can be planted over the system. Some of these grasses and wildflowers have extensive, wide-ranging root systems that can cause problems with system operation. Although having watertight tanks and piping goes a long way toward solving root issues, any type of vegetation that has a large, laterally ranging or deep root system would not be desirable.

We are fortunate in our region to have a lot of plant material options exhibiting compact fibrous root systems that, once established, can be colorful and require little maintenance. These plants also tolerate drought or low-water conditions, another desired characteristic of plantings over the soil treatment area. Examples of these plants include certain fescues, blue grama, little bluestem for grasses, and native wildflowers like prairie clover, certain native asters and the showy purple coneflower. For ornamentals, day lilies and numerous types of sedum varieties can be good choices.

We worked with the Horticulture Department at the University of Minnesota to develop plant lists for the state. Contact your county Extension Service office and they can put you in touch with someone who can help provide ideas of appropriate plantings for your area and climate.

TREES AND SHRUBS

What about trees and shrubs? Just as with other plants, trees and shrubs that are water-loving or have large lateral root systems should not be placed within 20 feet of the edge of the system. This is a minimum distance and a larger cushion is preferable. Examples of trees in our area that should be kept a distance from the system are poplars (aspen, cottonwood), silver maple, willow, elm and cedars. Again, check with an expert to see what is in your area and what the options might be.

We see a lot of problems with roots when we have worked in the Southwest. No surprise that some of the desert trees and shrubs are very aggressive at seeking water; particularly mesquite shrubs can present a lot of problems. In Arizona we get reports that non-native species present more problems than some of the native plants. Major culprits are palm trees, which were once a common planting. Fortunately, palms are being phased out due to their need for water, but the issue underscores that homeowner choices are often not the best choices where the septic system is concerned. This shows there is an ever-present need to educate your customers and provide them with alternatives.



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