December 1, 2007
Plant of the Week
Do you like having a green lawn 365 days a year? Do you like to mow, irrigate, and fertilize during the winter? Is it appropriate to overseed your lawn for the winter? These are just a few questions that you need to ask yourself before you overseed your turfgrass. Warm season grasses such as Bermuda and Zoysias go dormant during the winter months and can be over seeded with a cool season grass variety to maintain green color and adequate quality. This DOES NOT include St. Augustine grass which stays green-and-growing all South Texas “winter” long-unless we have a hard freeze below 20º F. To gather some insight on this topic, I used some of the information from Dr. Jim McAfee, Texas Cooperative Extension Turfgrass Specialist. The following is what he had to say about overseeding:
The best time to overseed the home lawn is late October through November, but more accurately after the first frost. Annual ryegrass is the fastest germinating variety and probably the cheapest. It looks very similar to perennial ryegrass with a dark green color and shiny leaves. Annual ryegrass grows quickly and requires frequent mowing (around 2 to 2.5 inch height) especially during late fall and early spring. Their water use rates are moderate and fertility requirements are low – maybe one to two pounds of nitrogen over the winter months. For a dense stand of rye grass, overseed at a rate of about 10-12 pounds of seed per thousand (33 feet by 33 feet) square feet. And keep the lawn irrigated for several weeks to ensure germination.
There are so many varieties of ryegrass to choose from. One of the varieties that Texas A&M suggests for homeowners in this area is Pantera, because of its beautiful color and minimal maintenance. This annual type looks and grows much like the perennial types, but it will die out faster in the spring and therefore doesn’t create as much a problem for the turfgrass growing in the lawn.
For more information and availability on other ryegrass varieties for this area, please contact Douglas King Seed Company at: 210-661-4191 or http://www.dkseeds.com/shop/.
How to Overseed?
Dr. Jim McAfee recommends aerifying the lawn 30 days prior to overseeding if possible. For some homeowners, this is not possible or too hard to do. Right before you overseed, scalp the lawn (NEVER scalp St. Augustine!) down as low as your mower will go. This will help get the seed down in contact with the soil, which is very important. Fertilize overseeded sites with a complete fertilizer such as 18-6-12 at five pounds per 1,000 square feet. Apply fertilizer immediately after seeding so as not to “burn” the young seedlings. After seedlings emerge, light applications of the 18-6-12 every three weeks at two pounds per 1,000 square feet will help produce a dense, healthy stand of grass. As soon as the seed is planted, start watering. Water lightly a couple of times per day until the seed start to germinate and grow – this is not like planting bermudagrass seed that you should water two or three times daily until the seed sprouts. If you water rye seed too much, it will rot.
Overseeding–Should You Do It?
Overseeding is defined as seeding onto an existing turf, usually with a temporary cool-season turfgrass (i.e. annual or perennial ryegrass), to provide green active grass growth during dormancy of the warm season turfgrass (i.e. bermudagrass). It is used extensively on sports fields and golf courses, and to some extent, on commercial sites and home lawns. Sports field managers and golf course superintendents overseed their turfgrasses primarily to offset the excessive traffic during winter play as well as to have a green, quality turf. But there are negative effects to overseeding. Competition between the cool and warm season grasses can be great, especially in the early spring when the warm season turf is trying to re-grow after winter dormancy-often referred to as ‘spring transition.’ If the spring is cool and wet, it will favor the persistence of the overseeded grass at the expense of the re-growth of the warm season grass. Improved turf-type annual ryegrasses typically have a better spring transition than do the over seeded perennial ryegrasses. In years that favor continued persistence of the overseeding, there can be significant damage to the bermudagrass turf. Another big negative with overseeding is if the existing turfgrass should be “scalped down” to provide a seedbed to favor a quick fall transition to the overseeding turfgrass. This scalping, along with the fall competition from the cool season grass prevents the warm season turfgrass from being able to store the necessary carbohydrates in the fall months. This means the turfgrass is going into winter dormancy in a weaker condition, with less stored reserves to recover well the following spring. If you have a great deal of traffic during the winter period at your site, then overseeding may be appropriate.
What About Overseeding Damaged Turf?
Overseeding this fall might lead to warm-season turf with some very serious problems next year. A healthy warm season turf being over seeded is severely weakened as it is from the competition of the aggressive cool-season turfgrass being planted into it. Overseeded warm-season turfs are weak and sickly looking in the spring when they transition back to the dominant turf – imagine what you will likely have, if you are overseeding an already thin turf this fall. Next year will be the easiest transition year you have ever had – know why? There won’t be a transition for a lot of us because there won’t be a warm season grass remaining! Instead of overseeding, you should raise the turf cutting height and make sure to apply a Winterizer fertilizer. Allow it to fully prepare for the upcoming winter by naturally hardening off through the day/night heating/cooling patterns of this time of year. You should also consider replacing large areas of damaged turf with Floratam St. Augustine, http://www.plantanswers.com/grass.htm until late November. Local turfgrass producers such as Milberger’s Landscaping and Nursery, typically sell 50-yard pallets of Floratam or by the individual piece. But remember; ONLY Floratam should be used to replace the damaged St. Augustine caused by previous problems.
Expect a lot of winter weeds in an area with a thin turf cover. The thin turf that has received some rainfall during the last couple of weeks is sure to be invaded by a bumper crop of winter weeds. If you are not overseeding, apply a fall pre-emergence herbicide AS SOON AS POSSIBLE. What is being used: these are the most common choices – prodiamine, pendimethalin, Balan plus oryzalin (Amaze) and dithiopyro (Dimension). All of these are excellent PRE materials, each with their own strengths and weaknesses.
Be very careful with late season cultivation events on warm season grasses. The weaker your warm-season turf is, the more likely the damage this winter.
Well, here we are with some information on that temporary cool season winter turfgrass called ryegrass. The decision is now all yours!!!
And as always,
Remember, Learn and Have Fun!
David Rodriguez is County Extension Agent-Horticulture, Bexar County. For more information, call the Master Gardener ‘Hotline’ at (210) 467-6575 or visit our County Extension website at http://bexar-tx.tamu.edu, click under Horticulture and Gardening.