It is no secret that homeowners all want the thickest, greenest lawn on the block. They seed it, spread fertilizer and pesticides, and water it regularly. They use chemical or organic methods to improve the health of their grass and keep it weed-free.
But what can you do when you’ve tried all that and your lawn just isn’t growing as well as it should?
Perhaps all those nutrients simply aren’t reaching the roots of your grass. There may be a very simple solution. The soil could be too compacted – or, more likely, there is a layer of thatch clogging the ground and preventing the water and nutrients from accessing the roots.
What is thatch
As time passes and grass dies, small bits and pieces of it gather just above the soil. This can combine with living grass shoots and stems as well as pieces of leaf litter or other lawn debris, and is called thatch.
A small amount of thatch (typically ½” or less) can be beneficial – it forms a dark, spongy layer above the dirt; as it is broken down by the microbes in the soil, the decomposing thatch provides important nutrients to the lawn.
Occasionally though, thatch builds up too quickly for the natural decomposition process to break it down. The remaining thatch forms a barrier that keeps air and moisture from reaching the roots and sending nourishment where the grass needs it most.
If the thatch layer is more than ½” thick, it can lead to problems – plants diseases or lawn pests – and should be removed. That will allow air, water, fertilizer and nutrients to reach the soil more easily – and will also help the lawn to drain more effectively.
Dethatching the lawn
Though some homeowners hire lawn services to dethatch and aerate their lawns in the spring, dethatching is really quite a simple process and the average lawn can be dethatched in less than a day.
How can you be sure if the lawn needs dethatching?
If water runs off the lawn without penetrating the soil, this could be a good indicator that too much thatch has built up.
Kneeling at ground level, examine the grass at soil level. You can also use a shovel to dig up a section of sod and dirt approximately 6” square; after knocking off the dirt, verify the depth of the thatch – if there is ¾” or more of matted, grayish-brown stems and debris above the soil surface, the lawn should be dethatched.
If there is less than ½” of thatch, it should be left in place. Dethatching unnecessarily or improperly can remove the crowns, the blades, and even sometimes the roots of the living grass.
When is it best to dethatch the lawn
That depends on the climate and the type of grass you’ve planted.
The lawn should be dethatched when the soil is fairly moist and the grass is actively growing. It should typically be done at the same time as lawn aeration: in early spring or early fall for cool-season grasses and in the late spring or early summer for warm-season – preferably after the lawn has been mown at least twice.
You should never, however, dethatch your lawn in the heat of the summer; nor should you do so under drought conditions or if there are less than 45 days left in the growing season. It may be too hard for the grass to recover if it’s not vigorously growing – or doesn’t have enough time to recover before doing dormant for the winter.
How do I dethatch the lawn
If you have an extremely large lawn, you can rent power dethatchers at most garden centres or heavy equipment rental outlets. These typically have a small engine and rotary tines to chop up and pull away the thatch.
The disadvantage to these machines is that they are usually heavy and awkward – they may also damage irrigation heads or other objects hidden in the lawn, so remember to flag these before dethatching.
For smaller to average-sized yards, simply use a rake. Though leaf rakes or hard rakes work reasonably well, it’s best to use a dethatching rake. This sharp-tined tool will dig deep into the grass to penetrate the thatch layer and rip the buildup away.
Begin by mowing the lawn to about half its normal height and watering it slightly to moisten the soil – it should be damp, but not soaking.
Next, rake the lawn with the dethatching rake, keeping the blades lightly in contact with the soil and using the same motion as you would for raking leaves. If you are using a leaf rake, you may need to add more pressure to penetrate the roots and break up the thatch.
After dethatching, a leaf rake can be used to collect the thatch; this can be composted, and most communities offer yard waste disposal with spring trash collections.
How to care for the lawn after dethatching
If you’re also planning to aerate the lawn, you should do so after dethatching it and removing the pulled-up thatch.
Please note that after dethatching, the lawn will look ragged and perhaps even patchy; if so, lightly over-seeding the lawn – and focussing particularly on the bare areas – can help the lawn to recover.
You should also fertilize the lawn, and keep it well watered as it recovers from the dethatching.
It will generally take between three and four weeks for the lawn to recover from dethatching and to show measurable new growth.
How to prevent thatch from accumulating
Though it’s nearly impossible to prevent entirely, you can slow the formation of thatch.
It’s primarily caused by overwatering, overfertilizing, or mowing too high; in order to reduce the rate of buildup, water and fertilize the lawn only when necessary. You can also mow slightly shorter – using a mulching mower will leave smaller pieces of grass behind, which are easier for the soil to break down.
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