Powder River Examiner -

Courtesy PR Extension Service

A few of the late summer and early fall weeds are very prickly, according to Powder River Extension Agent Mary Rumph.

“Field sandbur seeds stick to everything…shoe laces, socks, wool, and fur,” commented Rumph, “and it hurts your fingers when you detach them unless wearing gloves,” she added. The plant is a warm season, grassy annual weed, reproducing by seed.

The plant grows 8 inches to 3 feet tall, occasionally erect, but usually spreading horizontally and forming dense mats. A native of Europe, longspine sandbur is a nuisance throughout most of the US. It grows in cultivated fields, pastures and waste areas, but favors sandy or well drained, gravelly soils. It can be particularly troublesome to livestock causing injury to mouths, noses or eyes that come in contact with the mature burs.

“Sandbur is not difficult to kill with herbicide,” commented Rumph, “however, since it is a grassy weed, Roundup is most widely used, depending of the location of the infestation.”

Buffalobur is a yellow flowering forb with spines all along the stem and on the burs. The stiff spines can cause mechanical injury, but it usually is not eaten because of the spines. It also contains poisonous alkaloids. The herbicides dicamba, picloram, triclopyr, and 2,4-D can be effective in controlling buffalobur and should be applied prior to flowering. Spot treatment using glyphosate will also control buffalobur.

Puncturevine produces seed burs with spines so sharp and hard they commonly cause flat tires on bicycles and can even penetrate the soles of soft soled shoes or sandals. The spiny burs do an excellent job of dispersing seed via tires, shoes and hooves.

Puncturevine has a distinctive, low-growing, trailing, mat-like form. Its’ prostrate, green to reddish hairy stems grow to 5 feet long and are highly branched, radiating from the crown of the plant. When shaded or competing with other plants, the stems may grow more erect and eventually trail over low-growing species, shading them out.

The plant is characterized by hairy leaves that are 1 inch to 2 inches long. Leaves are pinnately compound with three to seven leaflet pairs per leaf. Leaflets are tiny and oblong. Puncturevine has a somewhat woody taproot that can grow to 8.5 feet deep. Bright yellow flowers are produced from late spring through early fall.

The flowers have five petals and four sepals, and are pollinated by insects. A characteristic gray to yellowish-tan, woody, 0.5-inch diameter burr then forms. It consists of five wedge-shaped nutlets, each of which has two stout spines. Three to five seeds are formed within each nutlet, and remain enclosed within the burrs. These burrs will often remain on the plant after it has been killed by frost, or are found on the soil surface after they break off or the plant dies and deteriorates.

Puncturevine can easily be killed with Roundup or 2,4-D. Try to spray before flowering. Once the plant produces the spiny burs, the seeds can remain dormant in the soil for several years. If you find a plant that’s already seeded, dig it up, being careful to capture the seeds. Use leather gloves to protect your hands from the burs. Dispose of it by burning. Small infestations can easily be controlled by hand weeding.

Most producers have reported these hostile weeds alongside the county roads and fear the possibility of them spreading into fields or pastures. Normally, they do not compete well with other vegetation; however, there have been reports of field invasions which makes control even more difficult.

If you need a positive id on any of these or other weeds, please contact the Powder River Extension Office 436-2424.