Winter Weeds… Is it A Side Effect of Aeration?

Winter weeds can be an unexpected nuisance for many homeowners trying to cultivate a healthy fescue lawn. Winter weeds in lawn areas can be caused by several things, but in addition to the break in weed control taken when seed is put down, they can be related to core aeration. In this article, we will explore how much core aerating contributes to weed development, and what the alternative solution may be.

For anyone with a fescue lawn, weed development is expected in the summer. This is when the fescue struggles, thins out, and even goes dormant, making it that much easier for weeds to break through and fill in the gaps. This is why it is standard practice to apply pre-emergent weed control in the spring to help prevent summer weeds like crabgrass and dandelions from gaining too much of a foothold.

Pre-emergent weed control works by halting the development of seeds right as they germinate, causing them to die before they can grow up to become a mature plant. Unfortunately, standard pre-emergent herbicides do not distinguish between weed seeds and fescue seeds. As a result, it is important for spring pre-emergent herbicides to have worn off in time for fall aeration and seeding.

Once the pre-emergent weed control has broken down, the lawn becomes fair game for fall and winter weed development. While there are some herbicides that can act as a pre-emergent for winter weeds without risking the success of fescue germination, these products are much higher in cost and as a result are rarely built into a professional program. Aside from weed control, the other factor influencing weed development in the fall and winter is core aeration.

The purpose of core aerating a lawn each fall is to increase the porosity of the soil system and as a result reduce compaction. This method of aerating the soil is also well suited to be paired with fall seeding because it can create a solid foothold for seed to germinate and develop. However, the process of core aerating is aggressive and invasive, which is why it can be attributed to an influx of winter weeds.

Core aeration involves using mechanical, hollow tines to dig into the soil from the surface. Cork sized plugs of soil are then pulled out by these tines and deposited on the soil surface, leaving thousands of holes several inches deep across the yard. This is a great amount of soil disruption, and this results in significant weed exposure.

Any weeds that grow in a lawn or its surrounding areas are likely to produce and drop some amount of seeds. Most of the time, only a few of these seeds are actually going to germinate and develop. As a result, a soil system can hold dormant weed seeds at different depths for years. Pre-emergent herbicides keep these seeds from becoming an issue, but the lawn becomes vulnerable in the fall when that pre-emergent has worn off.

Enter core aeration. When the soil is disturbed and older pieces of soil from several inches under the surface are brought up and reorganized, many dormant weed seeds are suddenly being exposed to fresh air, sunlight, and perfect moisture. That’s right… the aftercare given to fescue seed after it’s been put down is just as great for encouraging weed seed germination.

So, is core aerating to blame for winter weeds in lawn areas? Not exactly. Winter weeds are normal in a fescue lawn because of the typical break in pre-emergent herbicides and even post-emergent weed control as well as the additional care given to the lawn after fall overseeding. However, core aeration can be blamed for higher rates of these weeds than you would normally experience due to its disruption of the soil and the resulting exposure of dormant weed seeds.

However, there is an alternative to core aeration. Liquid aeration is an increasingly popular option during the fall for its convenience, efficacy, and lack of soil invasion. Because liquid treatments do not disrupt the soil surface, there is not the subsequent exposure of dormant weed seeds. To explore a liquid aeration option, be sure to contact your turf management service provider today!

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