Dethatch or Aerate Before Overseeding

To get high germination rates when overseeding, not only is it important to water the seeds, but also make sure the seeds and soil have good contact. Two of the recommended processes to achieve this are dethatching and aerating. Read below to learn which of the two the better option is.

Dethatching vs. Aerate

The decomposing grass, roots, and debris that accumulate on the lawn are what is called thatch. It blocks the contact between the seeds and the soil, therefore, preventing germination of seeds. Moreover, thick layers of thatch block air and water from the roots. It also becomes infected with bacterial and fungal diseases, as well as insects.

Thatch often happens due to thick lawns. It results in compacted grass that blocks air and water. Aeration may solve this, but it is only useful when the layers of thatch are thin. It does not work on thick layers, which may need removal. In that case, using a dethatching machine is necessary to remove the thatch and ensure higher seed germination rates.

What is Aeration

Vehicle traffic, pets, and children playing can compact the grass and lawn. As a result, the pores are reduced, which are necessary for the soil to hold water, air, and nutrients for the roots. This problem can be solved by aerating your lawn, which also helps in treating thick thatch buildup. It allows air and water in the soil that helps in decomposing the thatch.aerating

Aerating the lawn is done using a core aerator. This machine has hollow tines which are mounted on a revolving drum. As the drum revolves, the tines are pushed into the lawn, thereby extracting cores of soil about ½” to ¾” wide. Usually, the cores created by the machine are about 1-6 inches deep and 2-6 inches apart. Don’t use machines that push solid spikes as they can make the compaction much worse. Many lawn care professionals can help you with aerating your lawn.

What is Dethatching

You can use a vertical mower to dethatch the lawn. Vertical mowers have vertical knives capable of cutting through the grass, then pull the thatch onto the surface so it can be disposed of. The machine’s blade should be able to penetrate half of the thatch. In dethatching, you should do it in one direction, repeating at a 90-degree angle beginning from the first pass.

Extremely deep thatches might have to be dethatched a few times during the growing season. It is advised to do this at modest depths to avoid pulling them by the roots. The best time to dethatch is every other year during the spring. Cool season grasses are best dethatched in the fall as they grow abundantly in 60 to 70-degrees F then go inactive during the hot weather season.

Whether to dethatch or aerate depends on how thick the thatch is. If it is less than ½” deep, it is best to aerate the lawn before dethatching. It is a good idea to aerate first, because its cheaper and will do less damage to the grass. If the grass isn’t showing improvement, aerate one or two times a year. Dethatching is best done if the thatch is over 1/2”thick.


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