Description: Puncture
vine, also known as caltrop, ground burnut, goat’s head,
or tackweed, is an annual reproducing by seed. It has a taproot
from which the several stems are branching, hairy, wide spreading,
and 1 to 5 feet long. The leaves are opposite, dark green,
about 2 inches long, and pinnately divided into 5 to 7 pairs
of leaflets. The leaflets are ½ inch long, narrowly
ovate, and hairy. The flowers are on short stems arising in
the axils of the leaves. Each has 5 pale yellow petals that
mature into a flat, dry seedpod about ½ inch wide.
The seedpod breaks into 5 parts at maturity. Each section
has 2 sharp spines. The plant blooms from July to September
and matures from August to October.
Distribution: Puncture vine is found infrequently
growing in sandy soils throughout Iowa. It prefers waste ground,
parking areas, playgrounds, railroads, and roadsides. It may
be poisonous to animals. Seeds can remain viable in the soil
for many years, so disturbances can provide areas for germination
and plant growth.
What’s The Problem?: Sharp spines can puncture
bicycle or vehicle tires. The plant can be toxic to livestock,
especially sheep. Puncturevine can also impair recreational
opportunities by making a trip into infested areas very painful
from the sharp spines poking into skin, leather, etc.
Management Methods: Although generally not a major
pest in Johnson County, puncture vine can become a nuisance
in certain areas. The spines can be particularly hard on bicycle
tires. Puncture vine can be controlled by pulling plants out
of moist soil, but be sure to wear gloves to avoid spines.
Good grassland management and prescribed burning may help
to control or reduce infestations. Herbicides can also provide
effective control if they’re applied when the plants
are young and small. If herbicides are used, be sure the product
chosen is labeled for control of puncture vine, and, as with
any pesticide, read and follow label directions closely.
Photo couresy of Weeds of Nebraska and the Great Plains published by Nebraska Department of Agriculture
Photo courtesy of Washington State Noxious Weed Control Board