Grass on Clay


Dear Garden Doctor,
Would you know what is the easiest way to prepare clay soil or improve it before planting my buffalo turf grass for a small courtyard area? My wife and I for the past two years have been struggling with getting the grass to fully take in the front courtyard. Our backyard has been doing it fine, but the front is a heavy clay mix since the developers scraped off the top-soil and sold it before we came (so we’ve been told!). I’m going to dig it up and try again, do you have any other lawn tips for growing on clay – how I can get the best out of the grass?
Thanks so much in advance, Richard.

If your aim is also to plant a drought tolerant grass in the clay soil, then the deep-rooted buffalo grass is the perfect choice. A clay soil by definition will be made up of at least 35% clay. If moistened, clay soil feels sticky and will easily roll up into a ball. The clay particles are tiny and pack down on top of each other with small pore spaces which restrict water run-off through the soil. That is why clay soils become easily waterlogged. On the plus side they generally contain a high nutrient content for plant growth, though can be difficult to cultivate and become prone to expanding when wet and cracking when dry.

Soil Amendments

First, you’ll need to amend the soil it so that it becomes ideal for planting grass. Start with a light tilling to break up the clay, then apply some topsoil/compost. The key is loosening up the clay and spreading organic matter/compost throughout the area that you intend to plant. Some people use sand or gypsum to break clay soil up. I highly recommend using organic matter instead, it supplies the nutrients that the newly planted lawn will need.

Gypsum, otherwise known as clay-breaker is a quick fix used on the heaviest clay soils. If your clay is extremely heavy an addition of gypsum will help. Gypsum improves the physical condition of clay soil allowing for better drainage and root penetration. Uptake of other nutrients will also be assisted by the calcium content of the gypsum. If you’re lucky then gypsum will work on your clay. Spread generous amounts of gypsum when the clay is moist and fork it in.

For an existing lawn that is suffering on clay, gypsum worked in will also help. First aerate the lawn with a fork, then spread 1kg of gypsum per sq/m and rake in. If the soil is dry, water after applying gypsum. Generally, gypsum is best mixed into clay or heavy soils prior to laying turf.

It is always best to have a prepared soil laid before the lawn is planted whether on clay or sandy soil. For final preparations always top dress with a thick layer of compost over the area and work it through the soil. The best way to improve any soil type is to add large amounts of organic matter or compost. Add anything available such as compost, manure, seaweed, dry leaves, even shredded newspaper, then fork it in and work it into the soil.

Watering

All new lawn types need to be kept moist during their establishment phase to ensure there is adequate water between the turf and the soil. This means a new root system will form and establish the new lawn firmly into the new site.

Don’t over water, the soil needs to have periods of dry so that the roots will search deeper, becoming well rooted in the process. If possible, water early in the morning or in the evening so the lawn can absorb the moisture more effectively. If it’s been raining don’t water the grass at all. Watering early in the morning, then infrequently once the lawn is established is a general guide, and if rain is on the way hold off on watering both before and after – let nature do the work for you.

Mowing

Buffalo grass must be mowed at the right height to ensure the turf remains in the best condition possible. Take care with the mower. Never remove more than one-third of the green leaf blade at any one time. This can weaken the grass and cause it to dry out easily on the hotter days.

Mow the lawn to about 5 -6 cm high. To keep your lawn in maximum condition, mowing should take place on a regular basis. If possible don’t mow when the grass is wet. Lawns can be easily organically fertilised using a mulching mower or by regularly top dressing with compost.

The trend these days is for smaller lawns, they are easier to manage and require less water.

Dr. Kris
Garden Doctor Contact: gardendoctor@hotmail.com

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