Released August 26, 2008
MANHATTAN, Kan. – Not all lawn grass seed is created equal.
Different seed suppliers’ bags or boxes may say they hold the exact same turf species and variety. But, that may not be the whole truth. Those containers can also include trace contaminants – unwanted seeds.
“That’s one of the reasons grass seed prices vary so widely. Often, you really are getting what you pay for,” said Ward Upham, horticulturist with Kansas State University Research and Extension.
By law, lawn seed packages must list any weed and/or “other crop” seeds that are along for the ride, he said. The label must list these unneeded contents as a percentage by weight, not number of seeds. So, a small percentage by weight can still mean lots and lots of “other crop” seeds, so long as they’re tiny.
“Naturally, for weed seed content you want as close to zero as you can find,” Upham said. “In comparison, ’other crop’ seed may sound fairly harmless. But, that depends on what the other crop is and on the type of lawn you want. Typically, good quality seed should have 0.01 percent ‘other crop’ or less.”
The definition for “other crop” is any grass species that’s planted and grown for some purpose. It could be an ornamental grass, pasture grass, orchard grass or a different species of turfgrass.
“The label won’t list what it is, though, unless it makes up 5 percent or more of the contents,” he said. “Of course, the unknown contaminant could be something fairly harmless, such as a perennial ryegrass in a tall fescue package. But, it also could be something bad – for example, a weedy looking, grassy perennial that you can’t get rid of without killing your whole lawn.”
Upham warned that in recent years, K-State’s turf specialists have been seeing more and more lawn seed for sale that’s contaminated with two bad “other crops”:
- Orchardgrass, which typically contaminates tall fescue seed, most often the relatively inexpensive K-31 variety. Orchardgrass produces clumps that are faster growing, lighter green, and more coarsely textured than Kansas turf varieties. It literally sticks out like a sore thumb, Upham said.
- Rough bluegrass -- also known as Poa trivialis or just Poa triv – which usually arrives as an unnoticed contaminate of Kentucky bluegrass. Despite its common name, rough bluegrass is actually fine-textured. It also forms circular patches that blend in fairly well until summer heat arrives. Then, it rapidly turns brown, but that usually means it’s gone dormant and will live to green up again and again.
“Less than one-half of a percent of either of these seeds can ruin a bag of seed,” Upham said.
A bag of tall fescue seed with just 0.5 percent orchardgrass will average sowing 12 to 16 orchardgrass seeds per square foot, he explained. Kentucky bluegrass with a similar percentage of rough bluegrass content would result in about 25 to 35 small Poa triv seeds per square foot of lawn.
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http://www.oznet.ksu.edu/news/story/lawn_seed082708.aspx
Contacts: Ward Upham, 785-532-1438
Kathleen Ward, kward@ksu.edu
