Low cuts and poor drainage equals bad bluegrass on lawns
WASHINGTON – Tim in Winchester writes: “What are your recommendations for getting rid of “Poa” (annual bluegrass) and starting to make progress towards a healthy and beautiful lawn?”
Well Tim, annual bluegrass (Poa annua) is a short-lived winter weed that generally turns brown and dies in the summer. All bluegrass is in the Poa genus, and all bluegrass suffers in hot weather, but this one generally suffers until death.
Annual bluegrass thrives in lawns that drain poorly, that are trying to grow in heavily compacted soil, that are cut too low or that are over-watered. So for now, measure your cutting height and make sure your grass is 3 inches high after mowing.
Then in the fall, rent a machine called a core aerator and use it to pull plugs out of the lawn to relieve soil compaction and improve drainage. (Don’t do this before fall – aeration now would do more harm than good.)
Don’t water during any week in which we get good rain. When and if you do water, make it long, deep and infrequent, for several hours at a pop and no more than twice a week.
Cheap chemical fertilizers equal brown spots on lawn
Ray in LaPlata writes: “I have brown spots on my otherwise fairly healthy lawn. I’ve been told that the cause is a fungus. Do you know what causes the fungus? Is there something I can do to avoid the problem? A local service feeds the lawn four times a year.”
That’s two times a year too many, which leads me to believe that you have “brown patch” (Rhizoctonia solani), a fungal disease linked to overuse of the cheap, quick-release high-nitrogen chemical fertilizers that are also wreaking havoc with the Chesapeake Bay and other priceless local water resources.
Don’t let that service feed the lawn over the summer. Summer feedings always stress cool-season lawns, whether they are diseased or not. Switch to two natural feedings, once in the spring and once in the fall, and you will be patchy no more. The natural slow-release nitrogen in organic lawn fertilizers does not cause the kind of fast, lush growth that this disease thrives on and your lawn will grow more slowly and evenly as well.
Chickweed and clover? Your lawn is retaining water
Ray in LaPlata (the guy with the brown patch in his lawn, above) also noted that “the only weeds I have are chickweed and some clover.”
Both weeds are a sign of poor drainage and/or excessive watering, which can also lead to fungal problems like brown patch. With all the rain we’ve been getting, good drainage is an absolute necessity for having a nice-looking lawn.
So consider renting a machine called a core aerator and using it to pull plugs out of the lawn this fall to improve drainage and relieve soil compaction. But don’t aerate now – that would do more harm than good. And don’t water frequently – just along deep soaking once a week when we don’t get rain (which will hopefully be the case sometime this summer).
Clover feeds your lawn for you!
Irene in Frederick writes: “I didn’t feed my lawn last fall, but I did use corn gluten meal to feed and prevent crabgrass this spring and the grass looks great – but I also have tons of clover. What can I use to get rid of it now?”
Just your lawnmower. And relax: clover is better than harmless. It’s a nitrogen-fixing legume that takes plant-feeding nitrogen out of the air and uses it to feed your lawn gently every time you mow as long as you return your clippings to the turf, which you should always do. Clover is so beneficial that it used to be routinely included in grass seed mixtures up until the mid ’60s.
If you don’t want clover around again next year, feed your lawn in the fall as well as the spring. It often appears naturally in lawns that are starved for nutrients, almost as if nature was trying to help out, and don’t overwater – it appears more frequently in lawns that are always wet.
Also consider aerating the turf in the fall if the lawn drains poorly or if the soil is heavily compacted. But aerate first, then feed.
The dirty little secret of lawn care
We’re dishing out lawn advice this week, so let’s review the basics. The dirty little secret is that having a great-looking lawn has much less to do with chemicals vs. organic than it does with practical steps like cutting height and timing.
Never cut a cool-season lawn (bluegrass, fescue and/or rye) lower than three inches.
Never cut wet grass.
Keep your mower blade sharp.
Don’t cut during a dry heat wave.
Never feed a cool-season lawn in the summer.
Always return the clippings to the turf.
Don’t water during a week when an inch or more of rain falls.
When you water, do it deeply, infrequently and never more twice a week.
If you want to aerate your lawn to improve the drainage, which is almost always a great idea, do so in the fall – never the spring or summer.
If you want to overseed or sow a new lawn, do so in the fall, anytime from around Aug. 15 through the end of September – never in the spring or summer.
Do those simple things and you’ll never need a lawn-care chemical. But you will have the best-looking lawn on the block.