University of Illinois Extension

To Seed or Not To Seed

When spring arrives, many people think they need to over-seed their lawns even though it is probably not necessary, said James Schuster, University of Illinois Extension horticulture educator based in Cook County.

“In general, you do not need to over-seed a lawn that is just thinned-out due to the winter,” he said. “Instead, consider core aerification--only after several mowings--and/or fertilizing.”

Over-seeding, he explained, is done to diversify the turf to help reduce disease problems or to adjust for a change in sunlight.

“If a tree died or was removed so there is more sun, the shade-tolerant fescue may need to be replaced with a more sun-tolerant grass,” he said.

Some people want to roll their lawn because it is lumpy after the winter. Lumpy lawns are more likely to occur in low maintenance lawns. Rather than rolling the lawn which increases soil compaction and, therefore, more diseases and insect problems, Schuster recommends considering mowing higher or doing light fertilization.

“As the lawn thickens, the lumpiness will be reduced or disappear all together,” he said. “Over-seeding does not reduce lumpy lawns for any length of time, if at all, since adequate fertility is necessary for a thick lawn that is not lumpy.”

Spring seeding should be done as early in the season as possible. Early spring seeding reduces competition from the weeds which will try to germinate in the spring.

If possible try to seed or over-seed in the late summer, late August to mid-September.

James Schuster

“Spring seeding can be done in landscapes where there is no turf, where this is an erosion problem, though additional work must be done to keep seed in place on erosion sites, or where there are large dead patches or large areas that need renovation,” Schuster said. “However, if possible try to seed or over-seed in the late summer, late August to mid-September. At this time, grass seed germinates faster because soils are warm and the air is generally cool. There are also fewer weeds that will germinate at that time of the year.”