Crabgrass is a common weed that plagues lawns throughout the summer, creating unsightly, coarse patches of grass. As temperatures drop and the growing season ends, many people wonder if cold weather eliminates the troublesome plant. Understanding the biology of this weed is the first step toward effective long-term control, especially regarding its fate during winter.
The Annual Nature of Crabgrass and Winter Death
The answer to whether crabgrass dies in winter is yes, because the visible, mature plant is a summer annual weed. An annual plant completes its entire life cycle—from germination to seed production—within a single growing season. This differs from perennial plants, which use underground structures to survive dormancy and return yearly.
Once the first hard frost arrives in the fall, the above-ground foliage and the root system of the crabgrass plant are rapidly killed. The plant turns brown, shrivels, and leaves behind a vacant patch in the lawn. This demise is permanent for the individual plant that grew throughout the summer.
The dead plant will not regenerate in the spring. However, the plant’s annual nature dictates that its survival relies entirely on prolific seed production before the winter frost arrives.
How Seeds Survive the Cold Season
Before the mature crabgrass plant dies, it produces a substantial quantity of viable seeds that drop onto the soil surface. A single, healthy plant can produce tens of thousands of seeds, sometimes reaching up to 150,000. These seeds do not germinate immediately but enter a state of dormancy to survive the cold winter.
The seeds remain in the soil bank, protected by the insulating layer of the ground. They will not sprout until the environmental conditions are right, regardless of the air temperature. The crucial trigger for breaking seed dormancy and initiating germination is the soil temperature.
Crabgrass seeds require the soil temperature at a 1- to 2-inch depth to consistently reach 55°F for several consecutive days, typically three to five. This consistent warmth signals that the threat of frost is gone and the summer growing season is beginning. Once this thermal threshold is met, the new generation of crabgrass emerges from the soil.
Preventing Spring Germination
The knowledge that crabgrass seeds only germinate after a specific temperature cue allows for targeted preventative action in the spring. The most effective method for prevention is the timely application of a pre-emergent herbicide. This product works by creating a chemical barrier near the soil surface that kills the crabgrass seedling shortly after it begins to sprout.
The application timing is critical; the herbicide must be in place before the soil reaches the 55°F germination temperature. Homeowners often monitor local soil temperature maps or use a soil thermometer to determine the precise window. Applying the product too late, after germination has begun, renders the pre-emergent ineffective.
Cultural Control Methods
Cultural control methods can also reduce the weed’s success by making the environment less favorable for germination. Mowing the lawn at a taller height, such as three inches or more, helps because the shade keeps the soil cooler. This lower temperature slows or prevents the soil from reaching the 55°F threshold. Maintaining a dense, healthy turf also helps crowd out potential seedlings, preventing them from establishing in bare soil patches.