Wild Ones 2002 Archive

QUESTION #5: Use of Native Plants over Mound Systems

We live in the country and have a mound system that handles our sanitary waste.
The mound is a huge stupid looking thing that is currently covered with turf
grass and weeds - and it is a pain in the butt to mow because of the steep slope.

Do you have any practical experience with planting a prairie over a mound system?
Good results? Problems? Cautions? Any particular plants that would not be suitable?
Any plants that are recommended?

If prairie planting is acceptable on a mound system, are there any recommendations
on how to prevent soil run-off until the plants are established? Like some kind of
burlap or fabric? Any places where this run-off preventing material can be purchased?
I don't think straw would be wise because of the weed seeds. Thanks for any info you
can share.

-- Rich of Appleton, WI

RESPONSES:

6-20-02

We have a mound system in our prairie and we covered ours with native prairie plants.
After about 6 yrs when things were looking good we had the tanks pumped as per contract
and the service man told us not to let the deep rooted plants remain. He also told us
to get rid of the ant hills and burrowing animals that were disturbing the soil. He
said to mow the top of the mound for better aeration of the system. We have not had
problems with our system but 2 out of 30 people in our neighborhood have had to
completely redo their mounds before they were 10 years old. As for plants I have
lupine, butterfly weed, coreopsis, spiderwort, harebell, and regular lawn grass to
keep the soil in place. Good luck.

-- Beth of Verona WI

6-17-02

On the sides of our mound system, I planted in parallel:

1 row of red osier dogwood, then moving out

1 row of American highbush cranberry, then

1 row of meadow rose.

After 3 years, the mound is almost obscured, plus I now have songbird and wildlife
food and cover.

-- Tim of Wausau, WI

6-17-02

We have a native plant seed producer here in Michigan which markets a septic field
mix of seeds. You may wish to contact them for further exploration as to the
suitability for the mound system. Good luck. Michigan Wildflower Farm 517-647-6010 or

– Pat Ruta of Cadillac, MI

6-17-02

The same concerns apply here as a previous question about planting over septic
drainage fields. A mound system is similar except it is built above grade. Deep-rooted
native plants that can affect the seepage/treatment of wastewater and can plug the
distribution piping of mound systems need to be carefully considered. Its not what you
see above ground that matters so much as the below ground environment that is designed
and constructed to treat wastewater from your residence. Be careful not to affect that.
Check with the Department of Commerce, regulators of on-site systems and/or Jim Converse
or Dick Otis, Ayers Associates-Madison, statewide experts on on-site systems about this.

– Jack of Mt Horeb, WI

6-17-02

Click here: http://amerexcel.com/ American Excelsior Co.

Prairie Nursery turned me on to this company when I ordered seeds to plant on a stream
bank. They use a product called Curlex manufactured by this company. I found a
distributor locally and bought one 4 x 180-foot roll for about $70 and have made my
planting with plenty of the Curlex left over for future projects. The other size,
8 x 90, wouldn't fit in my car. It looks like the green mats that they use for highway
planting of turf grass, but it has no seed in it, so you put your seeds in and then roll
it out on top. If it works for Prairie Nursery, I'm sure it will work for you and me.
If you're using plugs, you would have to lay it out and then cut holes to put the plants
in. The fibrous material is easy enough to push around, but it is covered with a
biodegradable mesh, about 1 inch squares, not hard to cut with ordinary scissors

-- Pat of Lisle, IL

6-17-02

We investigated the planting of prairies on mound systems with the WI DNR and
UW-Extension many years ago, and were assured that the planting of native herbaceous
flowers and grasses posed no danger to the mound. Prairie Nursery has a "Septic System
Mix" specifically designed for planting in sand and gravel backfill used on septic
systems. If your system has had topsoil applied, which is standard in Wisconsin, this
mix will not work, but you can use another prairie mix that matches the topsoil placed
over the mound.

If you would like more information, please call Customer Service at Prairie Nursery
and they can fax or mail you a copy of a publication by UW-Extension on landscaping
mound systems with native plants.

– Neil of Westfield, WI

6-17-02

First, the University of Minnesota and Wisconsin Extension Service both have their own
publications of native plants (and some non-native) to plant on and near septic mounds
and within drain fields. The list of plants may be found on their respective websites
and both lists would work in your area. I personally have used plants from these lists
and have created others for more extensive plantings on top of a thin layer of planting
material above a cap for a landfill that has been retired.

Now to a more theoretical approach that I have also used though would require more
research on your part (though that is the fun part). Any plant that has fibrous roots
and will grow in dry conditions would work well in this condition. The fibrous roots
can not penetrate the septic system, cap or linear (including drain field), no matter
how long the roots will grow. So, Little Bluestem (Schizchyrium scoparium), the grama's
(Bouteloua spp.), prairie dropseed (sporobous heterolepis) are good grasses and most
of the bluff prairie, or dry prairie forbs like butterflyweed (Asclepias tuberosa) will
do well. The list can be pretty large of over 100 plants. Shade may cause the list to
be reduced though, many plants are still available like large-leaf aster (Aster
macrophyllus) and wild geranium (Geranium maculatum). Make sure that you have a good
mix of plants that will spread over the area to not create any bare spots to reduce
erosion (a good ground cover). You do not want plants that have a tap root like
dandelions do that may disrupt the cap. (Note from WOHostess: This would include the
silphium family as well.)

For the establishment and to prevent soil runoff, I recommend that you cover the
entire septic system or any slopes that are 4:1 (a slope that falls a foot in 4 feet
distance) or greater, 1:1 for example, should be covered with an erosion control blanket.
You can purchase these at most nurseries and even your local Home Depot or other hardware
type store. Blankets can be straw or coconut fiber blankets. Straw does not have seed in
it. Coconut lasts longer, especially in submerged water conditions, though is more
expensive. Either should work in the mound system, unless a ditch is made at the base of
the mound and then the coconut is more appropriate.

A seed mix would work well in the mound system, though I would add a plug mix of small
plants that will give the site a little instant color and gratification.

A lot of possibilities are available and more can be said, though I am trying to keep
this simple. If you have any questions or want more information please contact me
directly. (Note from WOHostess: If you wish to take Rusty up on his offer, please
contact WOHostess for further information. Please note Rusty speaks interchangeably
about Septic Systems and Mound Systems with respect to the appropriate native plants.
Although two entirely different systems, the information offered here applies to both.)

-- Rusty of Minneapolis, MN

6-17-02

As far as suggestions as to what Native plants will grow on the site, I would suggest
getting in touch with Dr. Gerould Wilhem. (gwilhelm@cdfiinc.com) Jerry did research on
which plants were thriving on top on the "natural area" built on top of Buffalo's land fill.

Regarding preventing soil run-off until the plants are established -- a good cover crop
of annual rye that gets mowed once or twice to prevent reseeding is the best way to hold
the soil until the prairie plants are established. The mowing doesn't hurt the prairie
plants which are busy building their root system the first year, and the rye combats
competition from the weeds.

– Melinda of La Grange, IL

6-16-02

This is the same as other discussions about planting over septic fields. I believe that
the state of Wisconsin did a study on mounds and found that natives do not harm the
system and may even help it. I also believe this is mentioned in the Prairie Nursery catalog.

I believe they have a plant list for such purposes. Give them a call to see what they have
to say. (800-476-9453)

-- Tim of Rockford, IL

– Mandy of Mequon, WI