Cenchrus longispinus

Mat Sandbur

Cenchrus longispinus or Mat Sandbur along the Colorado River near Parker, AZ	This undesirable plant is weedy. The burs are hurtful but beautiful.	In the fall the leaves and burs are red.
Lovely red burs are difficult to remove from anything.	I put this in a plastic bag and it even stuck into the plastic.	Base of leaf blade widens above the sheath.
The burs can have 50 spines.	The burs are even sharper than they look.	The individual spines have narrow bases compared to similar species.

How to Identify Mat Sandbur

  You can do a positive identification by touch. Just kidding. The seedheads of the sandburs with their frightening burs are quite different from other grasses. Sometimes the compact seedheads obscure the rachis. There can be 50 pointed spines per bur, more numerous than other sandburs.

Similar Species

  Mat Sandbur is similar to three of the other sandbur species in Arizona:
(1)Cenchrus palmeri (Giant Sandbur) has only one to three burs on each seedhead and they are much larger, up to an inch across!
(2)Cenchrus echinatus (Southern Sandbur) burs have many flexible, barbed bristles at the base, and these tiny "barbs-on-the-barbs" point toward the bases of the spines (unlike Mat Sandbur). Also, there is a single whorl of the larger inner spines at the top of the bur--Mat Sandbur has additional spine whorls and individuals.
(3)Cenchrus spinifex (Coastal Sandbur) burs have conspicuously fewer spines, up to 30, and the upper of these are flattened and have very wide bases. I can often find the ends of florets showing through and between the barbs as shown below right.

Mat Sandbur is the top row; Coastal Sandbur at bottom.

Mat Sandbur on left (with more spines), Coastal Sandbur on right with fewer and sturdier spines.

Perhaps you can see spikelets showing between the Coastal Sandbur spines.