More details about weed prevention through the season
WTOP Garden Editor Mike McGrath
Feed and prevent weeds in the fall with corn gluten meal
Diana in Northern Virginia writes: "What is the best time to apply corn gluten for fall weed prevention in our area? I know the rule for spring is when the forsythia begin to bloom. But I don't recall the time frame for the fall…"
I don't know that I've ever defined one, Di. Corn gluten meal is mostly famous for being able to feed a lawn naturally and prevent crabgrass seed from sprouting in the spring. But the researcher who discovered those properties, Dr. Nick Christians of Iowa State University, tells me that it also can prevent weeds with seeds that germinate right after the summer heat abates, such as dandelion, clover, plantain, henbit and common chickweed.
To give your lawn a perfect fall feeding and knock out those weeds while they're still seeds, Christians says to apply 10 pounds of corn gluten meal per thousand square feet of turf as soon as temperatures drop from the 90s down into the 80s or around Aug. 15, whichever comes first. If your lawn has been really stressed this summer, Christians recommends you apply another 10 pounds two weeks later. Late summer/early fall is when our cool season lawns should get their biggest feeding.
Just remember that corn gluten prevents all seeds from sprouting, so you can't overseed after the gluten goes down. If you want to do both, sow the grass seed ASAP and apply the corn gluten about two weeks after the new grass germinates.
And yes, this is brand new information about fall weed prevention with corn gluten. I never knew this before, so thanks to Diana for a great, great question!
The perfect time to sow a new lawn, or fix an old one, is almost here
Janice in Howard County has a timely question. She writes: "Is Aug. 15 the right date to seed a lawn? And how should we water the lawn afterwards?"
The window between Aug. 15 and Sept. 15 is to sow cool season grass seed -- bluegrass, rye or any of the fescues -- in the D.C. region, Janice. The idea is to sow the seed in warm soil so it germinates quickly, but to have it mature in the shorter days and cooler nights these grasses prefer so that the new turf is sturdy and well established by the time the first leaves fall.
And this mid-August to mid-September window is really the only sane time to try and establish a new cool season lawn. The soil is too cold for good germination in the spring, and then summer heat burns up any little bits of grass that did manage to poke up. But cool season lawns sown around Labor Day are almost guaranteed to thrive.
Watering after seeding
Yes, the period from Aug. 15 through Sept. 15 is the ideal time to overseed cool season lawns that have developed bare spots, or to tear up what you have and plant a brand new lawn. Either way, correct watering afterwards is crucial.
After the seed is raked into the soil or covered with a little topsoil or compost, water the area with as gentle a spray as possible for about 20 minutes every morning and evening until the seed sprouts. Then stop the evening watering and never water in the evening again.
Then, if we don't get rain, water gently for an hour every other morning for a week or two before dropping back to twice a week. Finally, progress to the deep watering once a week that's ideal for established lawns. Obviously, adjust this schedule for any rain we receive during this time.
Note: The initial short waterings and evening watering are for the germination of new seed only. Water an established lawn like that and it'll burn up in the summer heat.
Bare spots? Get ready to overseed and feed
If your lawn just has some bare spots, which is a natural development with clumping grasses like the fescues, you should get everything ready now to overseed and fill them in.
Spread an inch of compost over the entire lawn and then sow matching seed -- the same blade color and shape as your existing grass -- into the bare areas between mid-August and mid-September. Rake the seed into the compost and water daily until the new grass comes up.
The compost will provide the perfect seedbed for fast germination, and applying it over your entire lawn will give all of the grass a great, natural fall feeding. Feeding with compost also helps get rid of thatch, allows grass to achieve its greenest color and improves the structure of the soil underneath your lawn. Pretty nifty!