Why is grass dying under my tree?
Quick answer
Usually two things at once: not enough direct sun for your grass type, and the tree's roots taking most of the water and nutrients. Lawn grasses need several hours of direct sun a day. Raise the mowing height, water and feed the area more, and consider thinning the canopy, a more shade-tolerant grass, or mulch instead of lawn.
Why this happens
Grass under a tree has a double handicap. It’s shaded, so it can’t make enough energy, and it shares the soil with tree roots, which are very good at taking water and nutrients. The result is a lawn that thins out and gets worse closer to the trunk.
Light
Every lawn grass needs direct sun. The Turf Growers Association of WA’s figures give a sense of the range among the main warm-season grasses: at least 4 hours of direct sun a day for soft leaf buffalo, at least 5 for couch, and 5 to 6 for kikuyu and zoysia. If the area under your tree gets less than your grass needs, it will keep thinning whatever else you do.
Water and nutrients
Tree roots spread well beyond the canopy and take water before the grass can. Soil under trees is often dry even after rain. That’s why grass under trees usually needs more water and feeding than the open lawn, not less.
What helps
Raise the mowing height in the shaded area so the grass has more leaf. Water and feed it more than the rest of the lawn. Ask a qualified arborist whether the canopy can be thinned or lifted to let in more light. If you’re replanting, choose the most shade-tolerant grass you can (the Grass Type Picker compares them).
When to stop fighting it
In deep shade, accept that lawn isn’t the right plant. A mulched garden bed, stepping stones or a shade-loving groundcover around the base of the tree looks better than struggling grass, and it’s better for the tree too.
What you may be seeing
- Thin, pale grass that gets worse closer to the trunk
- Bare soil, moss or weeds under the canopy
- Dry soil under the tree even after rain
It depends on your grass and climate
| If you have… | What changes |
|---|---|
| Buffalo | Copes with a little more shade than the others; TGAWA lists at least 4 hours of direct sun. |
| Couch | Needs full sun; TGAWA lists at least 5 hours. Thins quickly in shade. |
| Kikuyu | Needs plenty of sun; TGAWA lists 5 to 6 hours. |
| Zoysia | TGAWA lists 5 to 6 hours of sunlight a day. |
Rows that match the grass and climate zone you've set are highlighted. Set your climate zone
What you can do
Count the sun hoursCheck first
Note how many hours of direct sun the area gets in the growing season.
Check the soil moistureCheck first
Dig a little after watering. Tree roots often leave the soil dry.
Raise the mowing height
More leaf helps grass make the most of limited light.
Water and feed more
The area competes with tree roots, so it needs more than the open lawn.
Let in more light
Ask an arborist about thinning or lifting the canopy.
Change the plan
In deep shade, a mulched bed, pavers or a shade-loving groundcover often works better than lawn.
What not to do
- Repeatedly re-turfing deep shade with a sun-loving grass.
- Piling soil over tree roots to level the area, which can harm the tree.
How much do I need?
A label rate of "20 mL per 100 m²" means: Rate 20, mL, per 100 m². Per hectare? Use 10,000 m².
How much you need
Enter your lawn area and a rate to see how much product and water you need.
What's next
Related grass types, weeds, pests and diseases
Related questions
Related guides
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Sources
- Turf varieties, Turf Growers Association of Western AustraliaMinimum direct sunlight by grass type. Accessed 3 October 2026.
- Healthy Lawns: cutting off one-third of the grass blade, UC Statewide IPM Program, University of CaliforniaMowing practice. Accessed 4 October 2026.