How to: fix the lawn
Most warm-season grasses stop growing when the nights turn cold, allowing weeds to get a foothold while your attention has turned indoors.
So now is the time to target terrors like bindii, wintergrass and dandelions and avoid seeding - and many years more weeding - before boosting growth for lush summer lawns.
Time to target terrors like bindii, wintergrass and dandelions
You need to know exactly what you're working with - both the lawn type, and the weed - so you can choose a herbicide suited to your lawn and its weed problem. Selective herbicides target specific weeds and can also damage some lawn species, such as buffalo and Queensland blue couch. If in doubt take a sample to your local garden centre, or email a picture to the Garden Clinic helpline.
3. Select your day
Choose a day when rain is not expected for at least another two days, when temperatures are below 21 degrees and there’s no wind. Avoid mowing the lawn for a week before spraying as the open wounds created by mowing will quickly absorb any herbicide, and damage or kill the lawn. Delay mowing a week after spraying to allow the weeds to take up the herbicide.
Measure the lawn to calculate the right amount of product to use: incorrect dosage can damage lawn or be too dilute to be effective. For this reason we prefer concentrates to hose-on packs, as they allow for more accurate application. Follow the directions on the pack and expect weeds to start to yellow off in 10-14 days. If dealing with winter grass, spray again after two weeks if new seedlings have emerged. Weeds with underground storage roots or bulbs, such as dandelion, can be treated repeatedly by spot spraying or painting with a non-selective herbicide such as glyphosate. If weedy survivors persist after your treatment regime, dig them out by hand.
Lawn fertilisers gradually make the soil more acidic, providing just the conditions favoured by bindii, clover and oxalis. So you can suppress weeds as well as improve growth by adjusting the pH of your soil. The easiest and fastest method to reduce acidity is by applying eco-flo lime, which is enriched with seaweed extract offering better uptake of calcium. Apply twice a year to counteract the effect of fertilisers.
Over time, little bits of dead grass collect just above the level of the soil. This is called thatch. A little bit of thatch is a good thing as it acts like a mulch, cooling soil, slowing evaporation and providing food for microbes in the soil, but it can build up too fast, creating a barrier that prevents air and water getting to where the lawn needs it. If the thatch layer is three centimetres or so, it is doing more harm than good. Mow the lawn to half its normal height, and use a de-thatching rake to remove the thatch. You might prefer to get professional help for this, which is best done in early spring.
Recommence your lawn-feeding programme in August in Queensland, September in coastal NSW and October in cooler temperate zones. Organic based fertilisers, such as ‘Sudden Impact for Lawns’, or turf-grade chicken pellets are the best for building soil microbes and structure while controlled release lawn food delivers trace elements. Aim to alternate any chemical fertiliser with organics to maintain a balance.
Cut to the chase
Maintain the good health of your lawn by setting the mower blades at the right height for your lawn type to avoid scalping, bald patches and sunburn. Cool season grasses such as fescue, blue grass and rye like a mowing height of 2-3cm, though bent grass will tolerate a tighter cut. Buffalo grasses, particularly modern varieties such as Sir Walter and Palmetto like to have a longer leaf. The optimum mowing height is 3-6cm, depending on how much shade the lawn gets. The higher the shade the more leaf is required to photosynthesise and keep the lawn healthy.