have a sweetgum tree in my front yard that appears to be healthy,
however it is beginning to leave a large circle of dry soil/grass
around the circumference of its roots. Do you have any suggestions
to prevent or minimize this?
(Liquidambar styraciflua), Maples and other trees tend to have
shallow root systems that compete fiercely with the lawn for water
and nutrients. Other trees that tend to have shallow root systems
include maple (Acer spp.), beech (Fagus spp.), honeylocust (Gleditsia
triacanthos var. inermis), linden (Tilia spp.) and elm (Ulmus spp.).
It is not surprising that the grass is thin and struggling to hold
its own under this tree.
As time goes on, I
expect the sweetgum’s
lateral roots will expand up to the soil surface and make mowing a
misery for you and the tree. While you can cover these roots with
soil and plant grass seed, that is not healthy for the tree in the
long run. And it will have to be re-done periodically as the roots
grow, creating a never-ending chore for you.
Groundcover instead of Grass
It will be easier
on you and the sweetgum if you are willing to replace the struggling
grass with a ground cover that is tough enough to compete with the
tree. It prevents you from wounding the tree roots with the lawn
mower, which creates an entrance for insect and disease problems.
You will not have to replace the mower blade as often, either! It is
ideal if the ground cover bed extends out to the dripline (ends of
branches), but even half the distance to the dripline is good.
Pachysandra around a Pin Oak
Do not Rototill
Although good soil
preparation is key to getting ground covers off to a good start, it
is not a good idea to rototill in the root zone of established
trees. Carefully choosing tough plants that you can plant around the
sweetgum’s roots without working up the soil is best. Simply create
a hole about twice the size of the ground cover plant’s root ball
and install the plant. Finish by watering well and mulching with an
inch or two of shredded bark or wood chips. If the existing soil is
truly horrible, you can work some compost into the top couple of
inches of soil and plant into that.
Be sure to plant
whatever ground cover you choose in staggered rows, as if you were
laying bricks. If you plant them in straight lines they will take
longer to fill in the area.
Brief list of ground covers that should
tolerate life under a sweetgum tree:
Green and Gold
(Chrysogonum virginianum) – This native, semi-evergreen ground
cover grows six to eight inches tall with a comparable spread.
Plants start out as softly rounded clumps, gradually growing
together to fill the area. It blooms with gold, star-shaped flowers
in spring, then sporadically through the summer. Tolerates sun to
partial shade and range of soil types as long as drainage is good.
Bishop’s Hat (Epimedium
spp.) – Also known as barrenwort, Epimediums are more tolerant
of dry shade than most plants once established. They spread slowly
on underground stems known as rhizomes and bloom in spring with
racemes of flowers in shades of yellow, red, lavender and white. The
new growth of many species starts out with a blush of red in spring,
and then hardens off to green. Bishop’s hat grows one to
one-and-a-half feet tall.
sp.) – Hostas come in all sizes and colors, from very tiny rock
garden favorites to large, bold-leaved specimens. Leaves range from
plain green to yellow, to white or yellow variegated to deep,
textural blue. They are tough, durable plants (except for their
susceptibility to deer damage!) and tolerate competition from trees
in stride. Well known as shade plants, all need shade from the heat
of the day, especially gold-foliaged varieties.
Hosta comes in varied colors
muscari or L. spicata) – This evergreen, grass-like plant is
grown for its dark green leaves. It grows about a foot tall with a
similar spread and blooms in late summer with a spike of lavender or
white flowers. Gold and white-variegated cultivars are also
available. This is a tough, durable plant that tolerates sun to deep
shade, road salt, and variety of soil conditions as long as drainage
is good. Liriope spicata is considered hardier than Liriope muscari.
It spreads by underground stems known as rhizomes and will fill in
the area without much prompting. Liriope muscari is a clump-former
and will take much longer to fill in the area.
Green-White variegated liriope (top)
'Big Blue' liriope (bottom)
Strawberry (Waldsteinia fragaroides) – Barren strawberry is a
native, semi-evergreen ground cover that closely resembles edible
strawberries. It grows four to six inches tall and spreads by
rhizomes. Barren strawberry blooms in spring with yellow,
star-shaped flowers. It tolerates full sun to part shade and a range
of soils as long as drainage is good.