Two closely related but different species of several summer annual grasses are common
in the low deserts. In general, these are all easy to distinguish from each other
in the field and they respond similarly to herbicides. Some of these and their distinguishing
• Watergrass (Echinochloa colonum) and Barnyardgrass (Echinochloa crusgalli)
These are very similar but watergrass has purple bands or chevrons on the leaves
and barnyardgrass often has awns or bristles at the end of the spikelets. Both respond
the same to herbicides.
• Red Sprangletop (Leptochloa filiformis) and Mexican Sprangletop (Leptochloa uninervia)
Red sprangletop is, in general, a lighter green color and has a finer seed head
than does Mexican sprangletop which is darker green or gray and has a visibly coarser
seedhead. Both form clumps or crowns that often survive through the winter months.
Both are fairly tolerant to Poast (sethoxydim) and Fusilade (fluaziflop) but are
controlled with high rates of Select (clethodim).
• Field Sandbur (Cenchrus pauciflorus) and Southern Sandbur (Cenchrus echinatus)
Both of these equally miserable weeds are only found in sandy soils and fairly easy
to distinguish. Field sandbur has thinner, gray colored leaves and yellowish burs
that are longer than broad. Southern sandbur has darker and broader leaves and fatter
red colored burs. Southern sandbur has a more compact seed head with distinctly
more burs than does southern sandbur. Both of these are fairly tolerant to Poast
(sethoxydim), Select (clethodim) and Fusilade (fluaziflop).
• Southwestern Cupgrass (Eriochloa gracilis) and Prairie Cupgrass (Eriochloa contracta)
These similar grasses are fairly easy to distinguish in the field. Southwestern
Cupgrass is one of the wider leafed grasses in the deserts. Prairie Cupgrass leaves
are not as wide and are hairy. Southwestern is more branched than prairie and the
ligule is shorter and less prominent. The branches are longer and fewer on prairie
than on southwestern Cupgrass. Both respond the same to most herbicides.
• Green Foxtail (Setaria viridis) and Yellow Foxtail (Setaria glauca)
Both green and yellow foxtail typically form clumps, produce lots of seed and stand
more upright than many other summer annual grasses. They are not difficult to distinguish
in the field. Green has a darker greenish or brown seedhead compared to the yellow.
The leaves of yellow are generally longer and have more bristles (5-20) per spikelet
than green, which typically has 3 or less darker colored bristles. Both respond
the same to most herbicides.
• Purple Nutgrass (Cyperus rotundus) and Yellow Nutgrass (Cyperus esculentus)
Right! These are not grasses. They are sedges which are much different. Sedges all
have solid triangular stems. They are perennial and reproduce primarily by below
ground tubers. Purple has bigger( 1/8” to 3/4” ) irregular shaped tubers that are
connected by rhizomes and have an almond -like odor. Yellow are smaller pea size
and round. They are not connected and don’t smell. Yellow is often taller and has
pointed leaves while purple has blunt shaped leaves.
(Photo by Barry Tickes)