Hey There, Turf-heads! It’s been a while!
Early in the month, a faithful follower, BigD, wrote:
What are your thoughts on a routine for a spring overseeding of a lawn and a pre emergent application? I overseeded (fescue) in the fall and I never see the fall growth like I want and over the winter I get concerned that I won’t see my bare spots fill in like I expect in the spring. I’m always tempted to reseed in the spring but my experience has shown that it is necessary to apply a PE soon after the last frost. I understand that the use of PEs affect grass seeds as well as weeds. What would you think of an application of grass seeds followed by an application of a PE? I assume there needs to be a certain amount of time to allow the new seedlings to sprout and become strong enough to withstand whatever the PE would do to hinder their growth. How much would a spring reseeding allow the new grass to outcompete potential weeds for nutrients in my lawn? I guess my questions are how long are PE effective (I use them regularly every spring and still have some weeds appear in summer & I know you advocate for a 2nd application) and when is it ok to apply a PE to a reseeded lawn?
PS. I’d love to see a post about moss, its effect on a lawn and causes/treatment
BigD asks a LOT of questions here, and brings up quite a few valid issues for spring reseeding. Here’s the short answer…grass seed sown in the spring seldom makes it past August. But if you’re looking at ugly bare spots, then spring seeding is worth it. And spring seeding makes weed control very challenging.
I’ll dispense with the moss question right away. If you’ve got moss, it’s a symptom of acidic, shady and wet soils, and usually, thin turf. A thick turf won’t let the moss grow. Test the soil for pH and apply lime accordingly. Are you overwatering? Can you limb up the trees causing the shade? Can you remove crappy trees to open up the area? Have you deadwooded the trees and thinned the crown recently? Have you tried to overseed grass species that are better adapted for shade, such as creeping red fescue, sheep’s fescue and meadow fescue? Turf in shady areas can be mowed lower than turf in full sun, so try mowing those areas at 2 inches instead of 3.5 to 4 inches. If it’s shady, that means there are trees, which means there are tree roots competing for nutrients and moisture. In addition to your regular fertilization program I’d recommend that you apply Milorganite lightly at least twice in the summer, say June 1 and July 15th, at a low rate of only 0.3 lbs of nitrogen per 1,000 sq ft. A 40 lb retail bag would treat 7,000 sq ft of turf. A 50 lb commercial bag of Milorganite would treat 9,000 sq ft. There’s no need to overdo it.
Now for the the long answer of the RESEEDING aspects…
By far, the best time to reestablish a new lawn here in St. Louis and the rest of the transition zone, is September to October. When I was with THE Turf Plan in Ellisville MO, we’d stop our overseeding efforts by October 15th to third week in October, because we couldn’t guarantee success after that. Success in this case means having a fabulous new lawn the following May.
If you have as few as 4 tiny seedling sprigs of grass per square inch in early November, I’d bet you’ll have a thick and lush new lawn in May. Grass seedlings thicken up by tillering–meaning new shoots. One tiny seedling in the fall can have hundreds of leaves by the following spring.
This past fall, I got bit in the ass when I attempted to reseed my front lawn, a mere 1,500 patch of grass, because I was forced to start late in October. I lost a massive pin oak and the stump wasn’t ground out until mid-October. It took me a 3 days to cart off a yard and a half of sawdust and soil, another few days to add new topsoil and lay the new sod. I reseeded immediately upon completion of my sod job, but recall that last October was a cold, cloudy and wet–dreadful conditions for starting new seedlings. Without exageration, I didn’t see ANY new seedlings last fall.
So what should BigD and I do now? Duh! We’ll reseed! But my advice differs quite a bit from the guys you’ll hear on the weekend radio shows. Some will tell you that you’ll be just fine by starting in May. I call bull sheet to this! I’m going to start ASAP, as soon as we get a week or so of 55+ degree weather. The soil surface needs to be slightly moist to dry. I’ll reseed my turf-type fescue blend on the heavy side–at least 5 lbs/1,000 sq ft in thin turf, and 10 lbs/1,000 sq ft in the bare spots. I intend to use a garden rake to scratch groves into the soil first, and I’ll topdress with 1/4 inch of bagged compost or cow manure. I recommend dark colored soil because it’ll warm up fast and stimulate rapid germination. By starting in February or March those new seedlings have a better chance to get a decent root system developed before the hot summer.
I wish I could find a classic research study conducted back in the late 1990’s by a good turf program–Iowa State University, me thinks. They reseeded on the first of every month (as best as they could) and then evaluated the resultant turf stand in June for quality, disease and thickness. Far and away, the best establishment dates were September and October! Turf that was reseeded in April and May was thin to dead in August, necessitating another round of reseeding (Sept and Oct). Turf seeded in March does better but tender turf seedlings won’t survive the summer if not irrigated. Fungicides greatly aid in new turf survival, too.
Thus, I’ll reseed very soon, and I’ll plan on aerating and overseeding the same turf again in September!
Tell me about crabgrass control…
Another reason we professionals reseed in the fall is because reseeding in the spring complicates the crap out of our crabgrass management programs! Remember, your best defense against crabgrass is a thick, healthy sward, but that’s obviously not the case if you’re asking about spring seeding. The best crabgrass prevention strategies utilize preemergent herbicides (aka PRE or PE) that are impregnated onto fertilizer granules. These are also the most economical products. You cannot apply a PRE crabgrass fertilizer in the spring and then try to sow grass seed after that. Rather than throw your money away, send it to me, so that I can keep writing these outstanding garden columns!
If you reseed as recommended above you CAN apply PRE herbicides in mid April, provided your new turf is at least 3 inches tall. After you’ve mowed your new 3 times you can use the same products, even if it’s earlier than mid-April.
There are several NEW herbicides that can be safely applied postemergence (POST) to kill crabgrass in seedling turf, which makes weed control a lot easier. One is Drive(R) (quinclorac) and the other is Tenacity(R) (mesotrione). Tenacity provides better weed control than Drive, so that’s the one I’d recommend. It’s safe for use on baby turf but only for Kentucky bluegrass, turf-type fescue and perennial ryegrass. It will cause thinning of the fine shade fescues like creeping red fescue but won’t kill it. It’s not safe on zoysiagrass and bermudagrass, thus it’s useful to keep these two species weakened with repeated use!
Both are relatively expensive, and they come in concentrated form. Both require a quality nonionic surfactant for best weed control, so don’t skimp on that! Be sure the surfactant bottle literally says these words–nonionic surfactant. Don’t use Dawn detergent no matter what those other dumb shits tell you! The use rate for Tenacity is ONLY 1 teaspoon per 1,000 sq ft! Store this product in a cool basement rather than your hot garage. The consumer-sized bottle is 8 oz, so you may want to supply the entire neighborhood! Learn more about Tenacity here: label
My fingers are tired, so I think I’ll stop here. I hope you enjoyed the detail and minutia! If you didn’t, to bad. Don’t ask for a refund!
Let’s hope for a NORMAL spring, not an abnormally warm one! I can’t handle frost damage…
Best to you all,