INVASIVE PLANTS - Technical Learning College

Blue mustard is a winter annual that germinates in the fall and produces a rosette with deeply
lobed leaves, similar in appearance to a dandelion. Blue mustard bears purple or blue flowers at
the top of the plant in March through April. Leaves on the flowering stems are coarsely toothed
and have wavy margins. The plant may grow from 1 to 1 1/2 feet in height. Two-inch long, beanlike
seedpods (siliques) that resemble "beaks" mature in early summer.
Control Herbicides are most effective if applied before weeds start to bolt in the spring. In the
spring, while it is actively growing, this weed can be controlled with an application of 2,4-D.
Henbit is a winter annual occasionally found in lawns in early spring. The lower leaves have a
stalk while the upper leaves clasp the stem. Stems are square, like other members of the mint
family. All the leaves are coarsely toothed and opposite from each other. Flowers appear in May
and are about one-half inch long, trumpet-shaped, pinkish white to purple, and form just above
upper leaves. This weed is more often found in buffalograss than in bluegrass. Newly-seeded
bluegrass and established bluegrass lawns with poor density may have some henbit.
Control Henbit has a taproot and is easily pulled from moist soil. Heavy infestations can be
controlled with triclopyr + clopyralid, 2,4-D or 2,4-D combination herbicides; at or prior to
flowering. Fall application of a pre-emergent herbicide (dithiopyr, isoxaben, pendimethalin or
prodiamine) will prevent henbit germination.
White Clover is a perennial that forms creeping runners. These runners will root at nodes. Many
people like clover in lawns, while others find white flowers and the bees they attract objectionable.
Clover is a legume which fixes nitrogen, so it is often found in lawns having low fertility. To
discourage it, increase turf density with proper watering, mowing and fertilization.
Control Triclopyr + 2,4-D combination herbicides or other 2,4-D combination herbicides can be
used. 2,4-D alone is not effective.
Buffalo bur, sometimes called Kansas thistle and prickly nightshade, is a tap rooted annual
weed. It bears long, yellow spines on stems, leaves, and flower heads and can grow up to 2 feet
high. Drought resistant, its highest occurrence is in dry, exposed soil. The oblong leaves are 2-3
inches long with deep rounded lobes and are covered with very dense, stiff, and sharp spines.
Bright yellow flowers can be seen in summer. In the fall, berries up to 3/8 inch in diameter are
enclosed in the dried flower parts and are filled with black, wrinkled, flat pitted seeds. Control of
this plant is important, as it is a host for the Colorado potato beetle. When mature, the main stem
breaks near the ground and the plant rolls like a tumbleweed, widely scattering the 8500 seeds
that each plant produces. Buffalo bur can be pulled when the soil is moist. Be sure to wear
gloves to avoid injury from the spines.
Control Herbicides should be applied between late bud to early flower. Dicamba, Triclopyr and
2,4-D can be effective in controlling Buffalo bur. Glyphosate in a 2% solution can be applied as a
spot treatment.
Puncture vine is a prostrate, mat-forming summer annual. It has small leaflets and small yellow
flowers with 5 petals. Fruits containing seeds are a sharp, spiny burr that can easily puncture a
bicycle inner tube (or gardener’s skin!). This weed is found only in thin, less vigorous turf given
insufficient water. It will pull easily out of moist soils. Be sure to wear gloves to protect your hands
from the burrs. You can discourage the growth of puncture vine by increasing the turf density.
Control A 2,4-D combination herbicide will work best on younger plants. Pre-emergent herbicides
such as trifluralin + benefin or dithiopyr applied in spring can provide some control.
Oxalis Oxalis corniculata The leaves of oxalis, also called creeping woodsorrel, have a shamrock
appearance and the plant is often mistaken for a clover. At night, or on cloudy days, the leaves
may fold up. With the arrival of cooler weather in the fall, leaves turn purplish in color.
Occasionally, some plants may have purple leaves all year round. Oxalis is a prostrate, creeping
perennial weed with stems that will take root where they touch the ground. Flowers are small and
yellow. When mature, fruits explode, scattering seed several feet away. This plant is more
common in thin, less vigorous turfgrass that is given too-frequent, light irrigation. It can be
discouraged by increasing the density of turfgrass using good cultural practices.
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