To aerate or not to aerate? That’s not really the question, say lawn experts. Periodic aeration – poking holes all across your lawn, often using a special contraption – is very good for your grass. According to researchers at Penn State:
“Mechanical aeration provides an excellent, and probably the only, means of correcting or alleviating soil compaction, which may be quite serious on many lawn areas.”
There is, however, a dilemma facing all of us in Charlotte who haven’t gotten around to aerating yet. The best month for aeration in our area is probably September. That gives tall fescue lawns at least four weeks recover and resume growing before first frost in early November.
So, is mid-October too late to aerate?
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Most Extension agents and local lawn care companies say it is OK to aerate now, in spite of some dissenting voices. Even supporters, though, set two conditions: Do it now – don’t wait around – and do it right.
In making garden decisions, you can’t simply rely on calendar dates, although these are very useful as general guidelines. This is particularly true for food crops, but it applies to lawns and the rest of the landscape as well. Gardeners must also consider actual conditions, particularly such factors as soil moisture.
Though it is hard to remember now, with scenes of major flooding in Columbia just down Interstate 77 from Charlotte, but August and September were very dry. The soil was hard, and aerator tines couldn’t penetrate the needed 2-plus inches. Once this recent rain soaks in, conditions should be excellent for doing the job right.
We also have a bit more time flexibility with lawns than you find farther north. Warm spells return after frost, and tall fescue and other cool season grasses should continue growing actively until early December.
Doing aeration right begins with knowing what kind of grass you have in your yard. Fall aeration is for cool season grasses that grow actively in autumn weather, for example tall fescue (our most common turf grass) or bluegrass. Bermuda grass and other warm season grasses are managed on a different schedule.
Most authorities agree that “core aeration” – using hollow spikes to pull little tubes of soil out of the lawn – works best at relieving compaction. Compaction occurs when soil particles become squeezed together, especially a problem with clay soils.
To thrive, grass roots and beneficial organisms and microbes need space for water and air. In natural ecosystems, worms, wildlife, roots and decomposition help keep soils open and healthy. For lawns, we have to take over those responsibilities.
For small yards, personally, I think a digging fork works fine, though garden centers sell hand aerators that make cores. For larger areas – big yards, churches and sports fields – a large aerating machine does the most efficient job. You can rent them (a good neighborhood cooperative project), or hire a company.
Wait until soil is evenly moist but not overly wet before aerating. With most equipment, you will want to make two passes, east to west, and north to south, or equivalent. You can leave the cores to break down on the surface, or scatter them around with a rake.
You will find enticing ads online and elsewhere for “liquid” or “chemical” aeration, where a product is applied to the lawn to relieve compaction. It sounds good, but the science isn’t there.
Researchers at Colorado State University evaluated “liquid aeration” products, which they found usually contained liquified organic matter (think compost tea) or soap-like substances. They dismiss the idea of chemical aeration as “wishful thinking,” since these materials cannot penetrate deeply or affect soil physical characteristics.
Put another way, imagine taking a shower in a raincoat, where you only soap up the coat.
You can do many other beneficial things when you aerate, including adding compost and fertilizer, and overseeding with new grass seed, but aeration is beneficial without them as well. A soil test is invaluable for deciding how much lime (ground limestone) to add, another task you can do when you aerate. However, if you don’t have time to get that done, you can still aerate.
There is another key to lawn success, in my opinion: Less is sometimes more.
For a beautiful and sustainable lawn, keep it a reasonable size you can easily manage, and make sure it is in full sun. You can aerate all day long in the shade, and it won’t help grass grow there.
Remember, too, the best site for a lawn is almost always the ideal spot for your vegetable garden. Whatever benefits tall fescue bestows, it makes really lousy salad.
Don Boekelheide is a freelance writer. Unicity3@gmail.com.