Why doesn't grass grow well under a big tree?

Under a big tree, you might find thin grass with patches of bare earth. Out in the sunshine, the grass looks thick and green. Why doesn't grass grow well under a big tree?

A blade of grass needs sunlight to help it make its own food. Its green leaves catch the light. Grass cannot fetch a snack, so it makes food right there in its leaves.

That food helps the grass grow new leaves. With enough food, grass can keep growing and fill in gaps. Making food is an important part of growing a thick, soft patch.

Above the grass, the tree spreads its leafy branches. Those leaves block much of the sunlight, making shade, a place with less direct sunlight. The grass underneath gets less light than grass in the open.

In deep shade, grass cannot make as much food. With less food, it grows more slowly and may leave bare patches. Too little sunlight is usually the biggest reason grass struggles beneath a big tree.

Sunshine is not the whole answer. Can you guess what grass needs that rain brings? Water! Grass needs water to grow, too, and beneath a tree, it shares that water.

Grass takes in water through its roots, the parts that grow into the ground. The roots draw water from the soil around them. They bring that water into the grass so it can keep growing.

The big tree has roots, too, and many spread through the soil near the top. They reach into the same soil as the grass roots. The tree takes up water there because it needs water to grow.

When the tree takes up water, it can leave less for the grass. Without enough water, grass grows less well. The tree isn't being unkind; both plants take the water they need from the ground.

Shade. Roots. Grass often grows poorly under a big tree because shade means less sunlight, and tree roots can leave it less water.

Next time you rest beneath a leafy tree, you can understand the quiet story of the grass below.