Commonly called goatheads, it is one of the most obnoxious and irritating of all weeds. Summer annual with prostrate stems radiating from a central root crown extending to 3 feet or more in diameter. Each seed pod has three pointed spines and each fruit separates into four or five three pronged burs, each containing two or more seeds. These seed capsules are very hard and durable, making them resistant to drought, moisture rot, insect feeding or predation by seed feeding rodents and birds. These capsules help preserve the seeds for up to 20 years. These sharp spines also provide this weed with an easy way to get its seeds spread around. Stems are highly branched and reddish brown on mature plants. Five pedal bright yellow flowers are borne from the leaf axil. From flowering to viable seed can be as short as 3 weeks. Leaves are opposite and divided into 3-7 leaflets on a short petiole. Can be toxic, mainly to sheep in early spring.  

Many people become frustrated trying to control Puncturevine.  It grows so quickly in the summer months that it can be difficult to keep up with.  The smallest shower seems to trigger more germination.  Very susceptible to most common herbicides.  It is essential that spraying commences at or before flowering.  A shallow rooted plant, it can be controlled with tillage.  It does have the capability to regenerate if the root crown is not removed.  Continued tillage is required during the season for new seedling.  Pre-emergent control with chlorsulfuron is the best initial treatment, followed by tillage or herbicide treatments later in the season.  
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You need to bag or burn puncturevines that have flowers because viable seeds can form even after being pulled.
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When using herbicides always read and follow label directions on any chemical. It’s the law!
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Information modified from “Selected Noxious Weeds of Eastern Oregon,” by Gary Page, Malheur County Weed Inspector.  Material for this feature is provided by Jordan Valley Cooperative Weed Area Coordinator Eric Morrison.