The timing of when grass starts growing in the spring is highly variable. The precise month a lawn emerges from winter dormancy depends almost entirely on the type of turfgrass planted and the local climate. This annual reawakening is not triggered by a calendar date or air temperature, but by consistent warmth reaching the soil beneath the surface.
Cool-Season vs. Warm-Season Grasses
Turfgrasses are classified into two major categories based on their preferred growing temperatures. Cool-season grasses thrive in the northern half of the country, performing best during the moderate temperatures of spring and autumn. Common examples include fescues, perennial ryegrass, and Kentucky bluegrass. These grasses enter dormancy when temperatures fall below 40 degrees Fahrenheit in winter or during the peak heat of summer.
Warm-season grasses are suited to the southern United States, flourishing in the intense heat of summer. Grasses such as Zoysia, Bermuda, and St. Augustine enter a brown dormancy when cold weather arrives. Their active growth cycle is shifted later in the year compared to cool-season counterparts. Knowing the type of grass is the first step in predicting its spring return.
The Critical Growth Trigger: Soil Temperature
The true signal for a grass plant to break dormancy is the sustained temperature of the soil. Air temperature is secondary because it fluctuates widely, but the soil acts as an insulator, providing a more reliable measure of spring’s arrival. This mechanism controls the timing of root and shoot development.
Cool-season grasses begin to stir when the soil temperature consistently reaches 40 to 45 degrees Fahrenheit, allowing minimal root growth to begin. Active shoot growth, which causes the lawn to visibly green up, accelerates when soil temperatures climb into the 50 to 65-degree range. Warm-season grasses require significantly more heat before they wake up. They need the soil to reach a sustained temperature of 55 to 65 degrees Fahrenheit to initiate green-up.
Regional Timelines for Initial Growth
The month grass starts growing is estimated by linking the regional climate to the required soil temperature trigger. In the Northern Zone, where cool-season grasses are dominant, the soil typically hits the necessary 40 to 50-degree range in late March or early April. This timeframe marks the first signs of greening, though growth remains slow until warmer conditions arrive.
For the Southern Zone, which relies on warm-season varieties, the later and higher temperature requirement pushes the timeline back. Grasses in this region usually begin visible green-up in late April or May, after the soil reaches the 60-degree threshold. A late cold snap or an unusually cool spring can delay emergence into late May.
The Transition Zone, covering the middle of the country, is the most variable, often containing a mix of both grass types. This results in an extended period of initial growth; cool-season grasses may begin growing in March, while warm-season grasses remain dormant until May. Monitoring local soil temperature is the most accurate way to anticipate the start of the growing season. Soil thermometers are useful tools for precise timing, as estimates are subject to local weather patterns.
First Steps After Dormancy Ends
Once a lawn shows visible signs of growth, a few immediate actions are beneficial for the season ahead. The first mowing of the year should use a higher-than-usual blade setting. Removing no more than one-third of the grass blade height stimulates lateral growth while avoiding stress on the newly active plant.
Delay the first fertilizer application until the grass is actively growing and has been mowed a few times. Applying nitrogen too early, especially to cool-season varieties, can stimulate excessive top growth at the expense of root development. For warm-season lawns, fertilizer should be withheld until the grass is at least 50 percent green, indicating the soil has reached 65 degrees Fahrenheit for nutrient uptake. Dethatching or aeration, if needed, should also be timed for this period of active growth to allow the grass to quickly recover.