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Why Won’t Grass Grow Under Trees?

Landscaping with Weigela Shrubs and Rock Retaining Wall

Every Kansas City homeowner would love for their landscape to be the best in the neighborhood. A lush lawn with healthy grass helps make a landscape beautiful and inviting. But if trees are a part of your landscape, you may have discovered that your turf either won’t grow under trees or is never as thick as full-sun areas of your garden. In fact, shady areas simply don’t sustain lush turf over a season. Today, we’re going to share why that is and what can be done about it.

The Three Main Reasons Why Grass Doesn’t Grow Well Under Trees

Understanding the three main reasons why it’s challenging to grow grass under trees will help you determine whether or not you should give it a try as part of your landscaping plan.

  1. Shade

Relaxing in the shade of a tree—reading a book, having a picnic, or taking an afternoon nap—is one of life’s great pleasures. For most people, lovely soft grass is essential to the experience. But grass (most types) loves sunlight. Grass can grow quite well for a time under a young tree in the Kansas City region, but as the tree matures, and its canopy develops, less and less sunlight can penetrate through, and the grass under the tree begins to struggle and then dies off.

Box stores selling “shade mixes” of grass seed would like you to believe that grass can do well in shade. This is not true. All forms of grass are essentially “full sun” cultivars in the Kansas City area. Fine fescue can tolerate more shade than other types, but it still does better in full sun. The “shade mixes” are often comprised of a percentage of annual rye grass that will sprout, giving you the impression that your grass has taken root, then it will decline or die after a few weeks/months.

  1. Competition for Moisture and Nutrients

Grass must compete with the tree for moisture and nutrients from the soil, and the tree usually wins because it can tolerate the drier, less fertile soil better than the more delicate grass can. If the tree’s canopy is relatively dense, this can also contribute to the soil’s dryness because less rain reaches the ground under the tree.

Mowing the turf under a tree can also jeopardize the grass’s survival because it makes it more difficult for the grass to retain water. Leaves that fall from the tree also make it harder for grass to grow if not promptly removed.

  1. Allelopathy

Allelopathy is a biological process wherein one of your plants produces biochemicals that impact the germination and growth, and therefore the survival and reproduction of your other plants. In landscaping, allelopathy isn’t always a bad thing. For example, by releasing allelochemicals, some plants act as natural weed killers in their surrounding area. However, allelopathy can have a negative effect on your landscaping when one plant’s allelochemicals interfere with the growth of another, as is often the case with trees and grass.

Some types of trees grown in the Kansas City region are more allelopathic than others, including Hackberry, Maple, Walnut, and certain Oaks. If any of these trees are part of your landscape, it will be difficult to grow healthy turf beneath them.

How to Help Grass Grow Under a Tree

The turf under a tree may not ever be quite as lush as the turf in sunnier areas of your landscape, but with proper care and the right type of grass, the results can be beautiful. As the Kansas State University Agricultural Experiment Station and Cooperative Extension Service wrote in its Horticultural Report, “When growing turf in shade, be prepared for thinner grass. A thinner stand of healthy grass is more satisfactory than a thicker one that dies.”

Keep the following landscaping tips in mind for healthy turf under a tree:

  • Choose shade-tolerant grass varieties such as fine fescue.
  • Seed in early spring or fall, at half the standard rate.
  • Fertilize moderately (two or three times a year), and use deep, infrequent irrigation.
  • Water more frequently than sunnier areas but avoid watering in the late afternoon or evening. Fungus can be an issue in shade.
  • Prevent foot traffic on saturated soil.
  • Mow a bit higher (three to four inches) than brighter areas to help retain moisture.
  • Keep the tree well pruned to allow as much sunlight through to the grass as possible.
  • Clean up any fallen leaves promptly.
  • Try to plant grass only under trees that receive a minimum of four hours of sunlight a day.

Alternatives to Grass

If you decide that the extra determination it will take to grow and maintain healthy turf under your trees isn’t worth the trouble, there are a variety of alternatives that can make your landscape look just as spectacular, but with less effort. Mulch and other ground covers are available to suit a variety of landscaping styles and personal tastes. A shade garden is another excellent option to show off your unique style.

If you’re in the Kansas City area and would like some help with a shady spot, or any other aspect of your landscape, High Prairie Landscape Group can help you achieve a unique, stylish outdoor living space that you’ll enjoy for years to come. Contact us today to get started!