What is aeration

Before you read any further, it is crucial that you have a basic grasp of aerating and its benefits. Please read the linked article to make sure you understand the foundations of aerating.

Green Thumb’s Opinion

The facts:

We service the Baltimore area (central Maryland). Geologically, Baltimore lies in a region of Maryland known as the piedmont region. The piedmont region contains clay soils, which are prone to compaction. Soil compaction is not good for turfgrass. Aerating 2 or even 3 times per year is most effective for minimizing compaction throughout the year. Therefore, we should aerate at least 2 times per year. Now, we have to address and resolve any issues related to aerating this many times. It is our belief that the right lawn care program can accomplish this task.

“Whenever aeration is done (as long as the soil is not excessively wet) it will help alleviate soil compaction for a while.”

– Ph.D. Turfgrass Science

Argument 1: Spring aerating increases your lawns susceptibility to moisture-related problems

The logic behind this argument is that spring is generally a wet season. Wet conditions are optimal for root rot and fungal diseases.

Here is our problem with this hypothesis. Moisture alone is not detrimental to grass. However, moisture with heat is a breeding ground for fungus. To negate this potential threat, we plan to aerate between March 1 and March 21. Before temperatures become hot and rainy April arrives.

Secondly, aeration, when done properly, increases the air flow to soil roots. That leads me to believe that moisture would decrease! Since the exchange between soil, air and atmospheric air increases after aeration, water will evaporate more quickly.

I do agree that aerating in April would be a poor decision, and lead to a muddy lawn. That is why our program only aerates between March 1 and March 21.

Argument 2: Aerating stresses the lawn. Stressing the lawn before summer makes the lawn more susceptible to drought and heat

This is another argument that we can get behind IF aeration is timed poorly. Aerating in late May will definitely expose the lawn to more severe drought and heat.

However, timing the aeration properly, in late winter or early spring, disarms this threat. Aerating well before summer allows adequate time for the lawn to recover. It also eliminates compaction and increases the overall health of the lawn. Therefore, the lawn will be entering summer healthier after being aerated compared to not being aerated.

It is also important to asses a lawn care program in its totality. As a part of our complete program, we apply potash fertilizer before summer. Potash helps the lawn over come stresses such as heat, drought, etc. This further reduces the rick of stressing the lawn by aerating before summer.

Argument 3: Overseeding is not as effective in the spring

We agree. Fall is the optimal season for overseeding. But, our opinion is that overseeding does not introduce any new risks. Overseeding is also most effective immediately after aerating. Given this information, why not overseed if we are also aerating? Sure, some of the grass seed may die. It is equally true that some of the seed will survive and create a thicker lawn.

Argument 4: Aerating helps grass grow, but it also helps weeds grow, too

This argument revisits the importance of timing. My former professor at the University of Maryland, College Park, Mark Carroll acknowledged this issue in our email exchange.

“Biggest down side to spring aeration is that it can promote the germination of annual grasses. I suppose if you do it early enough (before mid April) and then follow up with a [pre-emergent] herbicide within a week or two you can do it [without promoting too] much annual [grass] germination.”

– Ph.D. Turfgrass Science

Our timing, March 1 – March 21, is well before mid April. Our observation has been that crabgrass, the annual grass referred to, usually appears in May. Our program calls for a dithiopyr application in late April. Dithiopyr is a pre-emergent herbicide that stops weeds from germinating. Even better, dithiopyr has slight post-emergent properties that will kill crabgrass in its early stages.

Argument 5: Won’t using a pre-emergent after spreading grass seed, inhibit seed germination?

Again, refer to the timing of our program. We will be overseeding between March 1 and March 21. Kentucky bluegrass is the slowest species of grass to germinate, taking up to 2-4 weeks. Other species in our seed mix, tall fescue, and rye take 1-2 weeks and about 1 week to germinate respectively. Doing the math, almost all seed will have germinated by April 21, just in time for our dithiopyr application.

In the literature on dithiopyr, crabgrass is the only plant mentioned to be susceptible to the herbicide after germination (there are other intolerant ornamental and grass species mentioned, but none of them are used in our overseed mix). This leads us to believe that once grass seed has germinated, there is little to no risk applying dithiopyr.

Our conclusion

Spring aerating is beneficial for central Maryland lawns. Yes, there are some problems and risks associated with this practice. However, with proper timing and a complete turfgrass management plan, all of these issues are addressed. Therefore, the benefits of spring aeration outweigh any potential negatives. So, for the healthiest lawn, aerate in the spring and fall. If you want to do it yourself this spring, make sure that you have a comprehensive program to overcome each hurdle. If you would like the help of a professional, fill out the form below.

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