Lawns and large trees don't get along. Turfgrass can stunt the early root development of young trees, while trees usually win out in the long run as their bigger roots outcompete grass roots for moisture and nutrients and their canopies shut off the sunlight that grass needs to thrive.
When lawns struggle under and around growing trees, the best option is to replace thinning areas with plants that compete better in this new environment of dry shade and root competition.
Groundcovers to consider:
- Liriope
- Barrenwort
- Golden Ragwort
- Hardy Ginger
- Leadwort
Some shade-tough perennials to consider are:
- Hosta
- Hellebores
- Coralbells
- Wood Aster
- Variegated Solomon’s Seal
The lowest-care option is simply replacing dying grass with mulch to eliminate mud, weeds, and exposed tree roots.
But what if you really want to keep as much lawn under and around trees as possible? Is it possible for lawns and large trees to coexist?
Five strategies to keep the grass under trees healthy
1. Maximize sunlight
Counteract shade by removing the lowest set or two of tree limbs and by thinning excess branches higher up. Both increase light reaching the grass.
Just never remove limbs more than one-third of the way up the trunk and never more than one-third of the total branches.
2. Keep the grass damp
When the weather becomes dry, grass will require your assistance. Because tree roots are larger, they absorb moisture more quickly, causing the soil to dry out.
Grass roots are mostly found in the top four to six inches of soil, and they require about one inch of water per week, applied in half-inch increments twice a week.
When a heatwave approaches, the lawn loses its rich, green color and begins to yellow. This may be a good sign that it's time to start watering.
3. Good nutrition
Since tree roots are better than grass roots at absorbing nutrients from the soil, fertilizing the lawn regularly is very important.
Traditional lawn fertilizers usually require about four applications spread throughout the growing season.
GreenView’s Fairway Formula lawn fertilizers use a patented formulation of slow-release nitrogen to feed over 12 weeks, giving similar results with just two fertilizer applications per year.
4. Add shade-tolerant seed
Grass that’s thinning under trees can be thickened by an annual scattering of new seed, known as “overseeding.”
The best time to overseed is late summer to early fall – when the soil is still warm for good germination but timed so that the young blades can establish as the weather is cooling.
Overseed with grass varieties that are best suited to shadier conditions for maximum benefit. The fine-fescue family of grasses, which includes chewings fescue, creeping red fescue, sheep fescue, and hard fescue, performs best in cool-season lawns.
GreenView’s Fairway Formula Dense Shade Grass Seed Mixture, for example, is a fescue-heavy mix of seed varieties that’s ideal for use under trees and in other shady conditions.
5. “Top-dress” the lawn
Lawns under trees benefit from a light topping of compost or similar sifted organic matter to help with nutrition and organic matter.
This is known as "top-dressing," and it entails raking a quarter-inch of compost over the lawn. This can be done in the spring and/or fall.
Read more on top-dressing the lawn
If the trees are still winning…
If your lawn still looks sad after these five steps, consider replacing it with sod. Sod is live grass that is sold in carpet-like sections and laid on top of bare, loose soil. Sod provides an instant new lawn, but it has the potential to go downhill for the same reasons that thinned the last grass stand.
The above five strategies can help extend the life of sod, but if it thins or dies, repeated new rounds of sodding can be done.
To aid in sodding, a few inches of soil can be added to fill in between surface tree roots, but never more than three or four inches to avoid burying and suffocating roots, which can harm tree health.
Whether you’re sodding or seeding, maintain a mulch ring of at least a foot or two around tree trunks to keep the mower from damaging tree trunks and to eliminate the need to weed-whack grass growing up against tree trunks, which can accidentally damage tree bark.