The arrival of spring may be subtle in the southern tier of the nation, but it arrives nonetheless, bringing with it changing needs for maintaining a vibrant, healthy lawn. As strawberry season withers and snowbirds begin migrating back to their thawing Northern dwellings, those who make southern states their year-round home should turn their focus to their lawns.
“In south Florida grass grows throughout the year. But in central and northern Florida and other southern coastal states, despite sometimes still being green, grass will significantly slow its growth or stop growing entirely as the temperatures get colder and the days get shorter,” says Laurie Trenholm, University of Florida urban turfgrass specialist. A similar transition can be seen from the southern tip of Texas moving north through the state.
As the days begin to lengthen again, lawns spark back to life and start rebuilding roots that sloughed off over winter in preparation for a busy growing season. Here are some steps turf managers should take to help prime their lawns’ photosynthetic engines.
For the warm-season grass species that dominate the southernmost states, Trenholm recommends making 1-6 fertilizer applications of ½ to 1 lb. of nitrogen (N) each per year. The total pounds of N applied per year depends on the grass species and where it’s growing. Regional recommendations can be found by contacting local extension experts or on university turfgrass management web sites and will provide a range of total pounds based on how intensively the lawns will be managed.
While southern Floridians and South Texans can fertilize year round, those in the central and northern parts of those states and into the coastal states should wait until grasses are actively growing, often in early April or into May, depending on location, and continue throughout the summer.
For North Florida and the rest of the Gulf Coast states with lawns featuring warm-season grasses, Clint Waltz, University of Georgia extension turfgrass specialist, says to look to the thermometer to cue spring fertilizer applications. “Sixty five degrees is the magic number,” he says. “When soil temperatures hit 65F at 4 inches deep, that’s when you know grass is actively growing.”
Homeowners can purchase their own soil thermometer or monitor reports from various ag research stations and other monitoring sources. Waltz recommends starting to watch temperatures in late March and exercise patience.
“You can get in trouble with warm-season grasses if you fertilize too early in the spring,” Waltz says. “If the roots aren’t active, the nutrients can leach beyond the root system causing environmental issues. You also run the risk of increasing disease activity.”
Fertilizing before the plants are ready to truly grow causes shoot growth. The tender new growth is more susceptible to insects and diseases than mature grass and the plant isn’t growing fast enough to overcome and combat the challenges as it would later in the season.
Those facing fertilizer application blackout ordinances may have to make slight adjustments to their spring fertility strategy.
“Summer is when we would prefer to make most of our fertilizer applications because the roots are actively growing and reaching deeper into the soil profile for optimum uptake and utilization. However, many Florida counties have ordinances prohibiting fertilizing in summer,” Trenholm explains.
“If this is the case, Trenholm recommends the following workaround. For instance, if fertilizer is banned from June 1-Sept 30, she advises making an application prior to the ban using a controlled release fertilizer in May just before the blackout periods start and then use a more soluble fertilizer after the ban period is over.
“Home owners get irrigation wrong more than anything else,” Trenholm says. Watering rates need to be adjusted based on the season and grass species. “When plant growth slows in the winter, even in south Florida, one watering per week is typically plenty.” In summer, irrigation should be bumped to twice per week with spring falling somewhere in the middle depending on rainfall.
Spring can be a critical point for watering. “When we get those days where temperatures are in the 70s or 80s, the sun is shining, humidity is low, and night temperatures drop back to the 30s it can really dry out grasses coming out of dormancy,” Waltz says. “If you’re not getting ½ to ¼-inch rains every 2 weeks or so you probably need to do some periodic irrigation to keep the grass hydrated.”
Starting in late May, Waltz says, it’s generally necessary to get 1 inch of water on lawns per week through rain or irrigation. A crude trick, he says, is to set out a straight-sided container, such as a tuna can, to capture and measure rainfall and irrigation water to determine how much the lawn is getting.
Weed and Pest Control
The occasional weed popping up in an otherwise perfect lawn can set off a race for the herbicide. But in spring, Waltz suggests those with warm-season grasses, such as St. Augustinegrass or centipedegrass, fire up their mowers instead.
“Post-emergence herbicides can set back certain warm-season grasses that are in transition in the spring,” he warns. “Instead, let your lawnmower be your early spring weed control.” Make sure the lawnmower deck is set to the same height the grass was mowed in the fall as it entered dormancy, he says. Once temperatures hit 65F, then lawn managers can consider lowering the blades.
Pre-emergence weed control, such as what you would use to control crabgrass, should be applied by mid-March, Waltz says. But avoid weed and feed products. “For late winter and early spring, avoid products with nitrogen. Look for labels that list nutrients as 0-0-7. Usually the potassium is just there as a carrier.”
If disease has been a problem in the past, Waltz says late March or early April is a good time to make a preventative fungicide application. “Most of our warm-season grasses don’t have too much trouble with disease. It’s generally too hot. But if we get a tropical depression or something and it gets wet, that can increase disease pressure.” He notes following good practices for mowing, irrigation and fertility can help prevent these issues.
For suspected insect issues, Trenholm recommends getting confirmation from the local county extension office before applying a pesticide. “Pest problems can often be a result of improper cultural practices, so pesticides may not have any effect,” she says.
Compaction or improper soil preparation prior to establishing grass may leave lawns struggling and in need of aeration. Spring is an acceptable time to aerate warm-season grass lawns. But, again, Waltz advises holding off until soil temperatures hit 65F and grass is actively growing to facilitate recovery.