What the crown of a grass plant is and where to find it

Most people think of a lawn as a carpet of green blades. The blades are the part you see and the part you mow, but they are not the part that keeps the grass alive. That job belongs to a small piece of the plant called the crown. If you understand where the crown is and what it does, a lot of lawn care advice starts to make sense, from how high to mow to why some lawns come back after winter and others do not.

What the crown is

Every grass plant has a crown. It is a very short stem that sits at the base of the plant. Penn State Extension describes it as very small, just a fraction of an inch long, white, and completely enclosed by leaf sheaths. Because it is so small and wrapped inside the leaves, most homeowners have never seen one.

Grasses have three kinds of stems. The crown is one of them. The other two are the stems that spread sideways, which grow out of the crown. So even the parts of the lawn that creep and fill in start at the crown.

Where to find it

The crown sits between the roots and the shoot, near the surface of the soil. Above it are the leaves. Below it are the roots. It is right at the line where the plant meets the ground.

You can see one for yourself. Pull up a single grass plant with a little soil still on the roots. Rinse the soil away gently. Look at the place where the roots join the leaves. Then peel back the outer leaf sheaths, the rolled lower parts of the leaves that wrap around the base. Inside, at the very bottom, is a short, pale section. That is the crown.

It helps to do this once. After you have seen how close to the soil the crown sits, you will look at mowing height and scalped spots in a new way.

What the crown makes

The crown is where the plant builds almost everything else.

Leaves. New leaves grow from the tip of the crown, a point called the stem apex. Penn State Extension describes it as a small dome with ridges rising from each side. Each ridge is a leaf in the making. As long as that tip is healthy, the plant keeps making new leaves.

Roots. The roots that hold a mature lawn in place come from the crown. Penn State Extension notes that secondary roots are produced from nodes in the crown.

Side shoots, called tillers. Tillers are new shoots that grow from the crown and grow straight up. Each tiller is a new set of leaves next to the first one. More tillers mean more blades per square foot, which is what makes a lawn look thick.

Spreading stems. Some grasses send out stems that run sideways, either under the ground or along the top of it. These start from nodes in the crown too. They are how certain lawns spread into thin or bare areas.

Why mowing height matters for the crown

Here is the part that matters most for your yard. Since the crown sits so close to the soil, a mower set too low can reach it. Penn State Extension warns that crowns can be damaged by mowers when blades are set too low, and that this damage can be severe.

Even when the blade does not hit the crown directly, cutting too short takes away the leaves the plant uses to make food. Purdue University turf specialists write that mowing below the right height for your grass restricts root growth and makes the lawn more likely to be hurt by insects, disease, drought and traffic.

Purdue gives these mowing ranges for common Indiana lawn grasses:

• Kentucky bluegrass: 2.0 to 3.5 inches
• Perennial ryegrass: 2.0 to 3.5 inches
• Fine fescue: 2.0 to 3.5 inches
• Tall fescue: 2.5 to 4.0 inches
• Zoysiagrass: 1.0 to 2.0 inches

Purdue also advises mowing often enough that you never remove more than one third of the leaf blade at a single mowing. If the grass has grown too tall, they suggest raising the mower and bringing it back down to the normal height over a few mowings, rather than cutting it all at once.

What winter does to the crown

The crown also decides whether grass makes it through winter. Penn State Extension's guide to winterkill explains that crowns are where new roots, leaves and stems are produced, so damage to the crown is what kills the plant.

One common kind of winter damage is called crown hydration. During a thaw, the crown takes up water. If temperatures then drop quickly, ice can form inside the crown and break its cells. Penn State calls crown hydration the most common and destructive type of winter injury that is not caused by a disease or pest. It tends to happen in low spots where water collects in late winter.

Dry, exposed turf can also lose so much moisture from its crowns over winter that the plant dies.

What this means for your lawn

When a patch of lawn turns brown, the important question is not whether the leaves are green. It is whether the crowns are still alive. Brown leaves on top of living crowns can green up again. Dead crowns cannot.

That is why so much good lawn care is really crown care:

• Mow at the right height for your grass, and keep the blade off the crown.
• Take no more than one third of the leaf at a time, so the plant keeps enough leaf to feed its crown and roots.
• Watch for low spots where water sits in late winter, since that is where crowns are most at risk.
• Before you give up on a brown area, pull a plant and look at the base. A firm, pale crown means the plant may still recover.

The crown is small enough to fit on a fingertip, but every leaf, root and new shoot in your lawn comes from it. Protect the crowns and the rest of the lawn has what it needs to grow.