Our lawns can sometimes show yellowing or discolouring of grass blades that is a struggle to identify and treat. Often issues can be mis-diagnosed as more serious than they actually are, so let’s get into the most common cause of a yellow and/or dying patches of lawn.
Heat stress is a huge cause of yellowing in lawns, but the one that people jump to the least. Through the main heat of the year it’s important to be watering your lawn enough to keep it healthy and that will mostly do the job, UNLESS your lawn has become hydrophobic, meaning when you’re watering it’s hitting the soil and running off as if it were concrete. In this situation regular use of wetting agents will help to improve your soil, as well as aerating. If you are already using products on your lawn including wetting agents, it may be necessary to just fill a watering can with diluted wetting agent to pour on your stressed areas.
Shade or heat reflecting. Something obscure but important to be observant of with your lawn is shade and areas where heat can reflect. Heavily shaded areas will always struggle to thrive even if replaced with more shade tolerant lawn varieties. Sometimes cutting back excess branches is an option but often objects causing shade can’t be removed so a recommendation I often give is replacing the struggling lawn with something else like a fire pit area or garden bed for shade loving plants. Heat reflection off metal edging, concrete walls and the like can also cause additional heat stress in certain areas. For these issues I recommend additional hand watering and even some aeration. Video about hot spots
Fungal diseases can appear in lawns and cause serious discolouration including spots on leaves. If you have spots you’re worried about I recommend closely inspecting the grass blades so that from there you can do some detective work using google lens or looking up common fungal diseases to match up what you’re seeing in your lawn. Some key notes for dealing with fungal diseases as this article is not an extensive guide about them; but key cultural practices with fungal diseases are to mow with sharp blades, water less frequently and always avoid night watering, if you use a fungicide please ensure you read and follow all PPE recommendations on the label.
Well, the dreaded lawn grubs! Often in Facebook groups and the like people will see a dead patch and say straight away that it’s lawn grubs and sometimes, they’re actually right. The way to test for this is with a soapy water test to see if any little critters come to the surface in the 5-10 minutes that follow. If they do, you’ll need to treat them with an appropriate insecticide potentially with follow up applications until they are eradicated. With lawn grubs prevention is key, by using Åcelepryn at the start of every spring you will stop destructive grubs from growing in your lawn and doing serious damage.
Winter! Frost and cold weather can do a heap of damage to warm season grasses especially, sending them yellow as the season rolls on. We are very lucky in that in Australian climates we can keep our lawns green throughout winter with the right care including liquid fertilisers, a pigment once your lawn has stopped growing just like the sports stadiums use, and well timed granular fertiliser + thatch removal in autumn. My lawn programs can help you through this in much greater detail!
In each of these categories there is more to delve into but hopefully this has been a good guide of the basics to look out for and start out on your search to identify any issues in your beautiful lawn!