How To Mow A Heavily Thatched Lawn

Q

My Couch lawn is very badly thatched, it's very spongy and is now at a height of about 8 cm. How do I cut back the thatch without killing the lawn?

A

There are two ways to remove the thatch from an overgrown lawn, while managing and repairing the damage which will occur from it's removal.

NOTES:
- These de-thatching methods are suitable for most warm season grasses such as Couch, Kikuyu, Zoysia, Queensland Blue etc, but will not be suitable for Buffalo Grass.
- Always expect some parts of the lawn to die off a little from de-thatching, but try to minimise this damage by not mowing too low at any one time, and by keeping up water to heavily browned off areas.

The first method involves regular lawn mowing while slowly reducing lawn heights. To do this, adjust the lawn mower height adjuster to remove about a third of the leaf surface in the first mowing. The lawn will still be spongy and thatchy, but will reduce over time.

Mow at the same height the following week, and continue at the same height until the lawn is fully green again. Once the lawn is green all over, it's time to reduce mowing heights by another third of the leaf length of the grass.

Repeat the regular lawn mowing until the lawn is green again. And once again, reduce lawn mowing heights by another third. Keep repeating this process until you reach the desired lawn length and the thatch is all gone. Return to regular lawn mowing frequencies once the lawn is fully de-thatched and at the desire growing height.

Method 2 is very similar to the first method, but is more aggressive at the first mowing.

At the first lawn mowing, adjust the lawn mower height adjuster to a height which is about twice the height of the final desired cutting height. Example, if you want your finished lawn to grow at 20mm, the first cut will be at 40mm. However, if this method is too aggressive and the lawn is looking too brown during mowing then increase the height further to achieve a finished result which shows both green leaf and brown thatch.

If the lawn mower is clogging with clippings, make the first pass at a greater height, and the second pass at the desired height for the first cut.

For the next 1-2 weeks, the lawn will require more TLC in the way of extra watering, so be sure to double up your watering for this period of time to allow the lawn to recover from the shock it is in.

One week after the first cut, it's time for the next lawn mowing. Keep regular lawn mowing at exactly the same height as the first mowing until the lawn is all green again.

Once this happens, it's time to lower the height a little more. Mow at the lower height for the next 2-3 services and make sure the lawn is greening up nicely again. Once this occurs, your lawn should easily tolerate being lowered to your final desired cutting height.

Expect more continued browning each time the height is lowered again, however, as each new lawn mowing height is lowered - the browning should be less and less. And always best to remember the golden rule not to begin lowering the height again until the lawn is fully greened up and healthy again.