Issue 7, June 6, 2011

Ryegrass -- the Unexpected Weed

Homeowners tend to be impatient. They want a green lawn and they want it done yesterday. There's no shortage of seed mixes on the market and marketing campaigns for that magazine perfect lawn. But the time you spend doing a little homework before you buy grass seed is certainly time well spent.

The seed label should be carefully read and considered. Premium mixes will be found in blue, while less expensive mixes will have a white label. Often times the white labeled mixes will contain a certain percentage of annual ryegrass (Lolium multiflorum) which will germinate very fast - within a week if it's being watered. Although it is quick to establish, annual ryegrass will only live for one, maybe two years, leaving thin spots behind where the more permanent cool season perennial grass has not filled in yet. Also, it will die or get stemmy in warm weather. It has a very coarse texture, is often a lighter color, and requires frequent mowing. It is not recommended for use in any permanent setting. It can be used for erosion control on newly excavated sites. Annual ryegrass is also known as Italian ryegrass.

Perennial ryegrass (L. perenne) can be undesirable at times when it is mixed in with another turfgrass species that is slower growing. Low mow Kentucky bluegrass seed mixes are becoming more prevalent in the market. Surprisingly, they aren't necessarily the premium mixes that you first might think they would be. In order for a green lawn to be achieved faster, perennial ryegrass if often added to the mix. Usually, it will germinate in about 2 weeks if it's being watered. However, perennial ryegrass will grow much faster than the slow growing Kentucky bluegrass will. Tall weedy looking clumps are the result. With the heat of summer, the perennial ryegrass will slow its growth and with time, the Kentucky bluegrass will overcome most but not all of the perennial ryegrass. I've had two grassy "weeds" to identify this spring and I suspect this is the culprit on both.

Low mow Kentucky bluegrass seed mixes do have benefits that homeowners may like. They offer the homeowner (when established) less mowing. There are a few out there that really enjoy mowing, but I suspect the majority of us could easily find other things to do with our time. In addition, many of these grasses have not only been bred for slow growth but also for a darker green color that really makes a yard stand out. Keep in mind that these low mow types are very slow to establish. Slow establishment means opportunities for weeds to invade. Homeowners are reminded to be patient after seeding. Alternatively, if a faster growing species is blended with it, an uneven weedy appearance may temporarily be the result. (Michelle Wiesbrook)

Michelle Wiesbrook

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