Extension Educator, Horticulture
A few warm days in March and grass becomes the topic of conversation. Proclamations of "Gotta get home to fertilize the lawn" are heard throughout the land. I'm not one to take away a good excuse to get outside on a warm day, but there is still plenty of time for lawn activities.
As most lawn grass starts to green this spring, some areas may continue to resemble straw. Rather than loading up on green spray paint or fertilizer, spring is a valuable time to evaluate lawn conditions and start corrective procedures.
First determine why the grass is in decline. It may be too much shade in which case groundcovers may be a better option than lawn grass. Or it could be poor soil conditions. A thin layer of compost over lawns can help to alleviate minor soil problems and even out bumpy lawns. It's always best to correct major soil problems before reseeding or resodding. Many lawns can be enhanced by changing management practices. Improper management includes mowing turf too short at less than 2 inches and over-fertilization.
Lawns are often improved by increasing plant density through overseeding with perennial ryegrass. Kentucky bluegrass can be used if the existing turf is not too dense. In central Illinois lawns can be seeded from late March through April. The prime time for total lawn renovation by seeding is from August 15th to September 15th. Late summer seedings generally have less competition from weed seeds. Also spring seeded lawns may not have the extensive root system needed to withstand summer heat; therefore regular irrigation during hot dry periods is required.
One critical factor for successful grass seedings is good seed-to-soil contact. Lightly raking and rolling bare soil after seeding is recommended. If you are just trying to thicken an existing lawn, use a slit seeder or another type of machine such as a vertical mower to get the seed down in the soil. Seed scattered over existing turf is just expensive bird seed. Another factor for success is keeping the seed consistently moist as it germinates.
Contrary to popular belief, it is not helpful to apply large amounts of nitrogen fertilizer first thing in the spring on existing lawns. Fertilizing lawns in spring is beneficial; however as mom often reminds us, "all things in moderation". Heavy applications of nitrogen fertilizer in spring can cause serious lawn problems including many lawn diseases. Generally the best time for fertilizing is after the lawn has been mowed a few times, typically late April or early May.
Choose a quality lawn fertilizer containing controlled release, slow-release, or water insoluble nitrogen. All of these terms refer to nitrogen sources that release small amounts of nitrogen to the grass over an extended period, which produces uniform healthy lawn growth. Slow release nitrogen is especially important in spring.
Another common spring activity is crabgrass herbicide application. First determine if you really have crabgrass problems. Remember open soil areas invite weeds so a better option might be thickening the lawn by overseeding. Remember don't use crabgrass herbicides in conjunction with lawn seeding.
Crabgrass usually begins germinating around the end of April-first of May when soil temperatures consistently reach 55 degrees F. Preemergence crabgrass herbicides require application prior to crabgrass germination; therefore herbicide application during the first couple weeks of April usually works well. Organic preemergence herbicides made from corn gluten are applied earlier, generally in March. Many preemergence crabgrass herbicides are mixed with fertilizer; therefore a compromise in proper timing is needed. Be sure to read and follow all label directions.
So don't worry if you didn't get a chance to work on the lawn during our past few days of warm weather. Spring is here and there is plenty of time remaining. Click here for more information on lawns.