Quackgrass is a weed worthy of many names. In Latin its name
is Elymus repens, but is also referred to by a previous name, Agropyron
repens. It has an abundance of common names across the country,
including: couchgrass, dog grass, quickgrass, quitch, scotch, twitch
and witchgrass. Whatever you call it, this weed is a common problem on
many vegetable and berry farms, especially in temperate growing areas.
A native or Europe, it is also found in pastures, gardens, roadsides
and other disturbed but unshaded areas.
characteristic of this grass is its system of underground stems, or
rhizomes. The rhizomes allow quackgrass to spread out widely from the
‘mother plant’ in very little time. New shoots then sprout up from
nodes on the rhizomes, and these can survive on their own if separated
by mechanical cultivation. The rhizomes also provide a place for the
plant to store energy for future growth. These are some of the reasons
that quackgrass can be hard to control.
information is taken from the excellent fact sheet titled ‘Quackgrass
Management on Organic Farms’ produced by the University of Maine
Sustainable Agriculture Program.
Aboveground quackgrass stems grow from 1 to 4 feet high. These
stems and the upper leaves can be somewhat hairy but the undersides of
leaves are smooth. The plant can spread by seeds as well as
rhizomes. The seed spikes look a lot like those of Italian rye
grass, but if you roll them between your fingers the quackgrass spikes
will feel round and the Italian ryegrass spikes feel flat. Although
seeds contribute to long distance dispersal, local infestations of
quackgrass result from prolific rhizome growth. These rhizomes, in
addition to the fibrous root system, comprise 60 to 70 percent of total
plant weight. Rhizomes may grow more than an inch per day, extending 10
feet or more from the mother plant.
Quackgrass is a perennial,
so it needs a reservoir of energy to survive from year to year. This
energy is stored as sugars in the roots and rhizomes in the late summer
and fall, to ensure winter survival. The following spring, the plant
has a ready supply of energy, giving it a competitive advantage over
crops that start from seed. Quackgrass is most vulnerable just as the
shoots are emerging, when sugar from the roots is being expended to
promote new growth but the young leaves are not yet photosynthesizing
at full capacity, so little sugar is being sent back to the roots.
it is a cool season grass, the annual cycle of quackgrass starts very
early in the spring. During the hot part of the summer its above-ground
growth is limited, but below-ground rhizome production is greatest in
summer. In the fall the tops of the parent plants die off and the
rhizomes stop growing horizontally and instead form new shoots that
emerge from the soil. Even following repeated disturbance throughout
the summer, if soil moisture is adequate, quackgrass may begin to
flourish in the fall after most crops have been harvested or have died
Quackgrass management requires an integrated approach,
involving prevention, tillage, grazing or mowing to deplete the sugar
stores in the rhizomes, followed by a competitive crop to keep
surviving rhizome buds from flourishing.
suppression. For a small, recently established patch of quackgrass,
hand digging, a mulch such as a fabric weed barrier, and careful
monitoring may be sufficient. Disruption of the root system will cause
the grass to re-sprout profusely, because dormant rhizomes have been
activated. The new plants must be dug again before they have more than
four leaves, but several repetitions of this process will usually kill
For larger stands of quackgrass, repeated tillage
with a spring or spike-tooth harrow beginning in the hottest, driest
part of the summer is recommended. The goal is to expose the roots and
rhizomes to the sun, causing them to dry out. Rhizomes that have
adapted to drought-like conditions will be harder to kill in this
manner. The disruption will separate rhizome buds from their parent
plants and cause them to sprout, so tillage must be repeated when the
new plants put out three leaves.
Rhizome fragments buried in
the top 4 inches of soil tend to sprout at the same time, making the
shoots easier to kill at the correct stage, so tillage methods should
be designed to keep rhizomes as close to the soil surface as possible.
Tillage should be repeated every time new shoots come up and develop 3
to 4 leaves. If young quackgrass plants are allowed to grow any more
leaves, they will begin to send out new rhizomes, and they will also
begin accumulating new stores of sugar in the roots. Each tillage
operation removes the new shoot growth and forces the plant to sprout
again, until its below-ground food reserves are completely exhausted.
a significant number of quackgrass rhizomes can be killed in the first
year of management, at least two years of tillage may be required for
good control. If a quackgrass stand remains relatively thick after the
first year, tillage must be continued until the middle of the next
summer. The amount of cultivation needed to eradicate quackgrass can
vary with soil type. On lighter soils, two to three rounds of
cultivation may be sufficient, while it may take as many as six on
heavier clays. Once your perennial weed problems are under control, the
length of the summer fallow can usually be shortened.
intensive grazing can also be used to manage quackgrass. Mow as
close as possible to the soil level to reduce new rhizome growth.
Intensive grazing that encourages the animals to eat the shoots down to
the soil level would have a similar effect.
Following a sequence of repeated tillage throughout the summer, a fall
cover crop should be planted. Some examples of overwintering cover
crops include winter rye or rye plus hairy vetch. Another option is to
plant a winter-killed cover crop like oats or oats and peas. To prevent
quackgrass reinfestation in years without a summer fallow, competitive
fall cover crops such as rye or oats should be planted soon after
harvest of the cash crop. The key with fall cover crops is to establish
a good, competitive stand. This means you would want a seeding rate of
2 to 2.5 bushels per acre of oats, for example.
Quackgrass tends to spread from weedy field edges into fields, where
occasional tillage actually encourages it to spread by separating buds
from the parent plant. Field margins should be
because this causes the same sort of reduction in energy reserves as
repeated digging.Because it is important to prevent re-establishment,
tillage equipment should be thoroughly
cleaned following work in infested fields as rhizomes may be easily moved from an infested
area to a clean one.
Multiple strategies need to be employed in order to successfully manage
quackgrass. Of particular importance is well-timed tillage, repeated
when re-growth reaches 3 to 4 leaves. Thus, summer fallowing is
critical to controlling quackgrass if it is already well-established in
a field. If possible, take fields with quackgrass out of production
every other year for a summer fallow or at least try doing a summer
fallow every four years. Periodic fallowing of field edges should also
be performed to reduce movement of rhizomes into fields. Harrows with
S- or C-shaped spring shanks are particularly useful for lifting
quackgrass rhizomes to the soil surface where they will dry out and
die, weather permitting. Crop rotations that include vigorous fall
cover crops, both after summer fallowing and summer cash crops, can
help reduce quackgrass infestations.