landscaping around septic systems

We have a new house that we have to landscape around. The biggest problem is that we have to be careful what we plan due to the septic system. It is an evaporation system, with two huge cement tanks buried under the ground in the front of the house and plastic pipes running through the side yard. We are planting grass in a rectangle right above the biggest bunch of the plastic pipes, but what can go around it or by the cement tanks that will not grow long roots and dig into it? In looking at the planting information on the packages and in my Western Garden Book, nothing seems to mention root depth.

Below is an article entitled What to Plant Over the Septic System by Mary Robson (originally published in her Regional Garden Column for Washington State University Extension, December 6, 1998):

“As more and more people move into rural areas, questions about septic systems and landscaping have become quite common. This column deals with some of the basics. A new brochure from Washington Sea Grant called: Landscaping your Septic System, offers considerable detail on the subject and provided much of this material.

“First, be sure that the septic field is clearly identified, and you know where the reserve area is. Keep all construction away from these areas. Understanding the functioning of the system is vital. Get information. (Some of it is available in video form.) The drainfield will not work well if overloaded with extra surface water, so be certain that it is not in the path of downspout run off or irrigation systems.

“Sunlight and air circulation also help the drainfield perform properly. Avoid surrounding it with tall trees. (Some shade is fine, but you would not plant an oak on the edge of a drainfield.) Set up some barriers so that it is not compacted by frequent foot traffic. Occasional mowing or moving through the field to check the system is certainly fine, but you do not want the drainfield in the middle of a heavily used path.

“There are advantages to using plants over the drainfield. Plants do help provide oxygen exchange and contribute to evaporation necessary in the drainfield area. Choose plants with shallow, non-invasive roots. You do not want breakage or damage in pipes from root intrusions.

“Grasses are most commonly recommended for the septic area. Lawn can be attractive. Do not overload the system by watering it a lot. Meadow grasses or a mixture of turf grasses like perennial rye and some broadleaf flowers (such as yarrow) can also look good and require little maintenance. Several mixes sold as Eco-Turf or Fleur de Lawn have these components.

“Small, shallow-rooted ornamental grasses (for instance, Festuca ovina
\’Glauca\’ 4-10 inches) can also be good looking. Very tall grasses like Stipa gigantea are not appropriate. Avoid over-active plants like English ivy (Hedera helix), which is becoming a menace in forested areas by moving in and stifling trees.

“Edible crops are not suggested. Vegetable gardening requires frequent cultivation, and digging in the drainfield area is inadvisable. Also, the brochure notes that: Sewage effluent is distributed through the soil in the drainfield area. Any root vegetables planted in this area may be directly exposed to septic tank effluent.

“Other possibilities are low-growing ground covers. Some, such as bugle weed (Ajuga reptans) and vinca (Vinca minor) grow vigorously and would fill in quickly. The native kinnikinnick (Arctostaphylos uva-ursi) grows well in full sun but is slow to establish. A mulch around the plants may help with weed control while the plants spread.

“The green growing layer over the septic tank helps the system to function, adds to the appearance of the landscape, and should, ideally, be set up to allow easy monitoring and maintenance. Keep landscaping simple and straightforward, remembering that the object is the good performance of the system.”

To get more information on septic systems, contact your local health department. The brochure Landscaping Your Septic System (pdf) is available through the Sea Grant Program.

Here are links to publications that might also be helpful:

Mounds: A Septic System Alternative

Understanding and Caring for Your Sand Filter System

Care and Feeding of Septic Tanks

gardening on drain fields

I know ornamental grasses are generally okay to plant on drain fields, but does this include larger grasses such as pampas grass? How about larger Miscanthuses? Arundo donax? There are mature pampas grasses already planted on the site I’m planning for. I’m wondering if they should really “go,” and if so, is there something else that would give some height in this area without impacting the drain field.

Here is a link to the Miller Library’s Gardening Answers on planting ornamental grasses in drain fields.

Here is the relevant section:

Grass is the ideal cover for drain fields. Grasses can be ornamental, mowed in a traditional lawn, or left as an unmowed meadow. You can also try groundcovers and ferns.
The key to planting over the drain field is to select shallow-rooted, low-maintenance, low-water-use plants. When tank covers are buried, keep in mind that plantings over the tank–from inlet to outlet–will have to be removed every three or four years for inspection and pumping.

Planting your drain field will be much different from other experiences you may have had landscaping. First, it is unwise to work the soil, which means no rototilling. Parts of the system may be only six inches under the surface. Adding 2 to 3 inches of topsoil should be fine, but more could be a problem. Second, the plants need to be relatively low-maintenance and low-water use. You will be best off if you select plants for your drain field that, once established, will not require routine watering.

SOURCE: WSU Cooperative Extension – Clallam County

Thurston County, Washington, has some information about landscaping a drain field, including plant suggestion.

Additionally, the Pacific Northwest Gardener’s Book of Lists (1997, by R. & J. McNeilan) offers a number of groundcover lists for various situations, including groundcovers for dry sites, slopes, and sun and shade. The Miller Library has this book.

Here is an article from King County.

I would be concerned that the larger Miscanthus plants might develop massive root systems which go far too deep for the site’s needs. Also, Arundo donax is an invasive plant, so you should not use it in your landscape. The Washington Noxious Weed Control Board has further information on this plant.

You may wish to remove the Pampas grass (Cortaderia) as well, as it is potentially invasive, has a deep root system, and is a prolific reseeder.

planting over septic drain fields

I am looking for plants suitable for a septic drain field site. I have a very large north facing slope in open sun with a drain field running along the top half. I would like to plant low to no maintenance ground covers and low growing shrubs to cover this area. This is a focal point when driving up to my house so I want it to be eye catching and interesting year round.

I thought of heaths and heathers as a possibility, but I’m not sure if the root system is shallow enough. I also would like to include native ground covers such as ferns, Gaultheria shallon and any others that you might think would work, as well as ornamental grasses and perennial flowers for interest. Can you please offer a resource for planting over drain fields or a list of plants that you think would work?

Trees or large shrubs should be kept at least 30 feet away from your drain field. If you do plan to plant trees near a drain field, consult an expert to discuss your ideas and needs. Trees and shrubs generally have extensive root systems that seek out and grow into wet areas like drain fields. Grass is the ideal cover for drain fields. Grasses can be ornamental, mowed in a traditional lawn, or left as an unmowed meadow. You can also try groundcovers and ferns.

The key to planting over the drain field is to select shallow-rooted, low-maintenance, low-water-use plants. When tank covers are buried, keep in mind that plantings over the tank–from inlet to outlet–will have to be removed every three or four years for inspection and pumping.

SOURCE: WSU Cooperative Extension – Clallam County

Information can be found here.

Thurston County, Washington, has some information about landscaping a drain field, including plant suggestions, here.

Additionally, the Pacific Northwest Gardener’s Book of Lists (1997, by R. & J. McNeilan) offers a number of groundcover lists for various situations, including groundcovers for dry sites, slopes, and sun and shade. The Miller Library has this book.

on gardening near septic system drain fields

Here is the situation: I have six inches between the cement wall and the septic drain field. I want a green screen between myself and the neighbors on the other side of the short cement wall. What can I grow that will give me a green screen and not invade the septic system pipes? All I can think of is some sort of climbing vine, but I am not familiar with which root systems could be a problem.

You have a real challenge with your situation. Most of the literature says that you should not plant any large shrub or tree within 30 feet of a septic system drain field.

Roots growing into the drain field is a serious concern. They recommend consulting an expert if you do want to plant near a drain field.

Instead, you might consider installing an attractive fence and/or using containers to grow plants in. For example, Camellias can be grown on a trellis from a container. They are evergreen, and will also flower.

Another vine-like plant is star jasmine, Trachelospermum jasminoides. It is evergreen with fragrant white flowers.

tree roots and sewer lines

I have several sewer pipes that are getting plugged by tree
roots on my grounds. I have used a rooter to remove the majority of the
roots and know would like to detour their return by using a chemical
called Root Free. It is a Copper Sulfate Pentahydrate. Is this product safe for my trees if used according to label?

Here is a link to
information on this chemical from the Pesticide Action Network’s
database. This link leads to the Material Safety Data Sheet for Copper sulfate
pentahydrate.

This product is highly toxic to humans and aquatic life, but should not
harm the trees. My question would be whether it makes more sense to
remove entirely any trees with invasive roots, and replant with other
plants whose roots will not cause trouble with the sewer pipes, rather
than use copper sulfate. See information below from UGA College of Family
and Consumer Sciences Cooperative Extension Service:

Tree roots can enter sewage and drainfield lines and cause plugging of
the lines. Lines should not be placed near trees, and trees should not be
planted near lines. Remove tree roots mechanically or flush copper
sulfate crystals down the toilet to help discourage or destroy the roots
where the solution comes in contact with them. Some time must elapse
before the roots are killed and broken off. Recommended dosage rates are
two pounds per 300 gallons of tank capacity. No more than two
applications per year are recommended. Time the application of copper
sulfate to allow minimum dilution and maximum contact time. Copper
sulfate will corrode chrome, iron and brass, so avoid contact with these
materials. Used in recommended dosage, copper sulfate will not interfere
with septic tank operation. Neither mechanical removal nor copper sulfate
contact is a permanent solution for tree roots. Remove the trees for a
permanent solution to the problem.

Here are some links to more information tree roots and sewer lines and about planting on drain fields:

Tree Roots vs. Sewer Lines from the city of Paso Robles, CA.

Choosing Sewer Safer Trees

Planting on Your Septic Drain Field

And here are some suggestions for alternative plantings:

Landscaping Your Drainfield

If you do decide to go ahead and use the Root Free, by all means follow
the directions to the letter, as it is required by law. You may want to
check with Seattle Public Utilities Drainage and Sewer Maintenance to
make sure that use of this chemical in the sewer system is permitted:
206-386-1800