P&PDL Picture of the Week for
June 12, 2006

Annual Ryegrass is appearing in many new lawns this spring

Glenn Hardebeck, Turfgrass Research Agronomist, Department of Agronomy, Purdue University

There have been quite a few samples sent to the P&PDL this spring from individuals complaining of a wide bladed, weedy grass “invading my new lawn”.  When there is an undesirable grass mixed throughout a turf stand, it’s very important to correctly identify the weedy grass species to determine whether it is an annual or a perennial.  If the problem is a perennial grass, there are very limited control options available.  For most perennial weedy grasses in cool-season turfgrass stands, non-selective control of everything or mechanically removing each perennial grassy weed are the only alternatives.  Fortunately most of the “invaders” this spring on lawns seeded last fall have been annual ryegrass due to a mild winter.

Annual ryegrass is often found in lower quality seed mixes.  It was originally thought to be a good “nurse crop” because of its rapid establishment.  Unfortunately, it is very coarse textured and tends to grow faster than the desirable turf.  So, the wide blades shoot up rather quickly between mowings, adding to the poor uniformity of the turf stand.  All this would be tolerable, in most circumstances, if annual ryegrass would hold true to its name and die off rather than persisting in newly seeded or overseeded lawns.

Harsh winters or hot summers are required to push annual ryegrass out of the turf stand.  Until the weather removes the annual ryegrass, the turf area may require additional mowing to help reduce the poor uniformity caused by this quick growing, wide-bladed weed.  The best form of control is to avoid seed mixes containing annual ryegrass.

Click image to enlarge

Annual ryegrass

Annual Ryegrass is coarse textured and normally light green.

Annual ryegrass

Each group of seeds are close to the seed stalk branching alternately.

Annual ryegrass

Annual Ryegrass has clasping auricles.  Where the leaf meets the stem, there are claw-like parts that wrap around to the opposite side of the stem.

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service