Winter's residue--twigs, dead branches, and bits of human-made debris--should be cleaned up as the first order of business in readying your lawn for spring work, said a University of Illinois Extension horticulture educator.
"These items are best picked up, sorted, and disposed of before any lawn care efforts can get under way," said Richard Hentschel. "Use this time to look over your lawn and note those areas that will need special attention, such as the shady side of the house or underneath large shade trees or areas that stand water after a rain. Take a visual inventory of grassy and broadleaf weeds."
In areas where the grass has started to thin, Hentschel said to consider probable causes like soil fertility, the amount of sunlight reaching the ground, or too much water.
"In many cases, trees can be limbed up enough to allow early morning and late afternoon sun into the yard to maintain the lawn," he said. "In some situations, weedy trees and shrubs may have grown up along the property line and can be removed to allow more light in to your yard as well.
"Letting that early morning and late afternoon sunlight into the year can make the difference."
If soil fertility or a changing soil pH is the suspected cause, have a soil test done and treat per recommendations. Soil compaction could also be a factor. Those areas near the driveway entry and next to the front door are common locations for compacted soil.
"If you have knotweed growing in those areas, that is a good indicator of compaction," he said. "Core aerating can help alleviate soil compaction."
Standing water problems can be improved by addressing surface drainage. Top-dress the area to remove the low spot or re-contour the area so the water is able to escape. Test these areas separately when doing a soil test as soil that is consistently wet or moist will have a different pH level than the dryer areas in the lawn.
"When the shade gets too dense to grow even the most shade-tolerant grasses, consider mulching the soil under those trees or using plants that prefer to grow in lower light levels," Hentschel noted. ""Annuals like impatiens or perennials like hostas and ferns are good examples."
After the big pieces of debris on the lawn are gone, homeowners can lightly rake the lawn by hand using a spring tine rake. Anything more severe removes the grass plants themselves. If the concern is the thatch layer, de-thatching is best done later in the summer.
"If you have a lawn roller, fill it with water about one-third full to press the grass plant crowns down to make contact with the soil after the winter freezing and thawing has caused the grass plants to heave out of the soil," he said. "This activity allows the grass plants to get their roots back into the soil a little sooner."
Re-seeding is done on areas that had grass growing before and are now bare. Over-seeding is done on areas that have grass but in thin stands.
"Adequate soil temperatures are necessary for the grass seed to germinate and grow," he said. "The soil needs to be a least 50 degrees or warmer. If the soil is too cold, grass seed will not germinate and a portion of the seed typically fails to germinate and sprout because of being wet and cold too long.
"In northern Illinois, April works best; in central Illinois, the middle of March through the middle of April is beat; and in southern Illinois, March is a good time to put out grass seed."
Surface preparation for re-seeding means lightly breaking up the surface of the soil and adding soil to the area if it is low to reduce standing water after a rain, which may be the cause of the thinned turf. Apply the seed and very lightly rake the soil and seed together to place the seed in direct contact with the soil.
"If the lawn just needs to thicken up, then over-seeding can be done," said Hentschel. "Using regular garden soil, top-dress the low areas between the existing grass plants to even out the surface before applying the seed. Lightly rake the seed into the soil as before.
"Water the areas with enough water to moisten the soil but not to make mud. Grass seed needs moisture to start the germination process, but no so much as to cause it to rot."
Hentschel said you can wait for Mother Nature to provide moisture, but whether it is provided by nature or the homeowner, once the seed receives water, the soil must be kept moist.
"You should see that 'green fuzz' begin to show up in four to seven days for ryegrass and 10 to 14 days for bluegrass," he said.
Source: Richard Hentschel, Extension Specialist, Green Industry Programming, firstname.lastname@example.org
Illinois Green Industry Association