Tuesday, September 12, 2017

Fall Lawn Maintenance: Core Aeration

In north-central Ohio, where I was born and raised, aeration was for golf courses and other high-traffic grassy areas; the average homeowner rarely, if ever, aerated their lawn. The soil there had a high humus content, drained well and didn't compact easily. Conversely, in the North Carolina Piedmont, our heavy red clay soil is essentially brick waiting to happen, and the only thing we can do to prevent that is annual core aeration.

Like dethatching, core aeration comes down to a do-it-yourself versus pay-someone-to-do-it decision. The difference is that while there are viable manual and lower-cost methods for dethatching, core aeration requires a fairly pricey piece of equipment or a tremendous amount of labor. There are, to my knowledge, no reasonably effective electric aerators, although a manual device that resembles a cross between a pitchfork and a shovel can be had for around $35. I suppose if you had a VERY small lawn this might work, but even then the idea of aerating a lawn two holes at a time is daunting from both a time and physical effort standpoint. Some gardening catalogs sell "aerators" that are long spikes which attach to the bottom of shoes. My guess is that those are just about as useful as they sound.

Core aeration is the process of removing plugs of soil roughly 3/4 inch in diameter and 2 to 3 inches in depth from the top layer of lawn. Most power aerators will remove six to eight of these plugs per square foot. This serves two purposes. Primarily, it opens the soil up so water and nutrients can reach the grass roots, and secondarily it reduces the physical density of the soil, effectively "un-compacting" it. Without annual aeration, red clay soils become very dense and do not promote deep root growth. When grass has shallow roots, it becomes susceptible to drought and disease and does not grow as full. As an added benefit, the removed plugs break down on the lawn surface, providing an excellent medium for the growth of new seed.

Walk-behind gasoline-powered core aerators sell for $800 and up, putting them out of the reach of most homeowners for this once-a-year project. Rental stores typically charge $50 to $75 for a half-day rental, but you will definitely need to book in advance, since just about everyone wants to aerate during the same 3-4 week period in the fall. Also, be sure that delivery is included with the rental. These machines are very heavy with lots of sharp points sticking out of them and they will do a job on your truck bed, not to mention your arms, legs and torso. If you own a riding lawnmower, core aerator attachments can be purchased for as little as $180, making them a reasonable investment for owners of larger lawns.

Most landscape and lawn care companies offer core aeration either as part of their regular maintenance program or as an ala carte service. Rates for a typical suburban lawn run $100 to $200 and often include overseeding. Frankly, if there is one lawn maintenance activity that begs outsourcing for the average homeowner, it's core aeration. The equipment is expensive to rent relative to the cost of the service, and it is physically demanding to use... sort of like a jackhammer on wheels. If you do go that route, however, be sure to get a firm date and time from the contractor, because you will need to prep your yard in advance. In fact, whether you choose to D-I-Y or outsource, there are three things you need to do in advance of the aeration to ensure your property is protected and your lawn gets the maximum benefit:

  1. Clearly mark the location of all irrigation sprinklers, underground "fence" wires and other in-ground equipment you do not want destroyed. The aerator will penetrate as deep as 3 inches. That's not deep enough to cause concern for underground utilities, but it can cause problems for shallower items. I didn't consider this the first time I aerated and knocked out my Invisible Fence. 
  2. Remove any dead grass or loose debris from the lawn, cut out any interfering tree roots and fill any resulting depressions with top soil. We discussed dethatching last week, and that process should remove most of the loose debris. If you have shallow tree roots that need to be cut out, you should do this prior to aeration. The aerator will not do a good job in rooty areas. 
  3. Thoroughly water your yard 24 to 48 hours before you aerate. Ideally, wait to aerate after a couple of days of rain, when the soil is wet, but not saturated. Unless you own an aerator and can be extremely flexible, however, it's difficult to time that out perfectly. In lieu of rainfall, you will want to put a minimum of 1 inch of water on your entire lawn 24 hours in advance. Aerating soil that is either too dry or too soggy does not yield good results. Note that it may take several hours to deliver an inch of water across an entire lawn, depending on the type of sprinkler you are using. 

The power aerator is used somewhat like a lawnmower, but is a much heavier device with a much wider turning radius. If you try to stop at the end of a row and make a pivoting turn, like you do with a walk behind mower, you will most likely rip up a divot of lawn the size of a card table. Instead, get a feel for the natural turning radius of the device and don't make any turns sharper than that unless you completely disengage the core pluggers. It goes without saying, I hope, that you will want to keep children and pets safely indoors while you are using the equipment.

If you thought your yard looked bad after dethatching, just wait until you see it right after you have finished aerating! The good news is that those individual plugs of soil that somewhat resemble, uh... Baby Ruth bars, will begin to break down with the first good rain. Which brings us to the next step and next week’s discussion, overseeding.

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