Does Watering a Lawn Protect It From Frost?

What Is Frost?

• Frost occurs when water condensing out of the air freezes on the surface of plants and the ground. This doesn't always happen in a uniform layer -- it's affected by wind and air pockets formed in low areas such as valleys. So one side of your house can experience frost while the other side is clear. One side might have been protected with a tree line or the side of your house. Freezing temperatures are not required for frost to form; the colder air sinks to the ground, making frost possible when the air just above the ground is above freezing.

How Watering Protects Grass

• Watering your grass before a frost is expected serves a couple of purposes. It helps the grass be well-hydrated. Low temperatures and wind can quickly dry out your plants, but watering them just before a frost prepares them and helps prevent dessication. Also, moist soil retains four times as much heat as dry soil, according to Cornell University. This keeps the soil around the grass' roots warmer so your lawn can survive the cold temperatures.

How to Water

• You must give the grass blades time to dry before the frost hits. This means watering during the daytime, preferably early in the day. Give your grass a long, slow bit of irrigation, with the goal of deep watering rather than fast watering. This keeps the soil moist at depths sufficient to warm the entire root system instead of just the top layer. Plan to water until the soil feels damp at least 2 to 3 inches below the surface.

Watering During Frost

• Some commercial plant growers use a specialized irrigation system to keep plant leaves or grass blades damp during a frost. This system keeps water moving across the plants to prevent frost from forming. This kind of system isn't usually feasible in your yard; it uses a large amount of water and can overly saturate the soil, which can be more damaging to the grass in cold weather than the frost. Irrigating the grass the day the frost is expected and giving the blades time to dry is a better method to protect your grass from frost.