UNIVERSITY PARK, Pa. -- Homeowners instinctively know when it's time to mow the grass, but many lawn jockeys might appreciate guidance on the right times to perform other types of turfgrass maintenance.

"Unless there is severe drought, or extended periods of cold or heat, homeowners can apply lawn treatments at roughly the same times each year," says Peter Landschoot, associate professor of turfgrass science in Penn State's College of Agricultural Sciences. "For example, homeowners in southeast Pennsylvania should apply crabgrass treatment from March 15 to April 15."

Landschoot offers a yearly calendar for various types of lawn management:

Seeding

Establishing a new lawn from seed should be done in late summer to early fall. "There are fewer competing weeds in the fall, and the soil may be too wet in the spring for good seeding," Landschoot says. "The new grass also will have two cool growing seasons in the fall and spring before experiencing heat stress the following summer."

Overseeding

Seeding onto thin turf or bare patches can be done in late winter, spring or early fall. Landschoot say perennial ryegrass works better for overseeding than any other turfgrass species. "It's very important the grass seed comes into contact with the soil and has space to germinate and develop," Landschoot says. "Don't just throw the seed onto dead grass. It won't germinate. The soil surface should be roughed or scratched with a rake."

Sod

Homeowners can apply sod at any time of the year, if irrigation is used. "If you sod in the summer, you'll need to water more frequently, and grass will take longer to establish," Landschoot says.

Fertilization

Grasses generally need more nitrogen and potassium than soil can naturally provide. A soil test can determine how much fertilizer your lawn needs. Soil testing kits are available for a nominal fee at Penn State Cooperative Extension county offices and most garden centers.

Once homeowners have determined how much fertilizer is needed, they can apply fertilizer once in late spring and again in late summer and/or early fall.

"If your soil test reveals the soil is too acidic, with a pH lower than 5.5, lime should be added," Landschoot says. "Apply it in fall, spring or winter because rain or snow helps work the limestone into the soil."

Dethatching

Thatch is the interwoven layer of dead grass roots and stems lying directly below actively growing turfgrass.

"Thatch can be bad for lawns because turfgrass roots can grow into the thatch, making them susceptible to drying out," Landschoot says. "You can remove thatch with special dethatching machines or aeration machines."

Landschoot recommends removing thatch in cool weather, preferably late spring or early fall. "Don't remove thatch during periods of high temperatures, drought or winter dryness, when the turfgrass can be subject to drying out."

Aeration

Lawn professionals aerate soil by removing soil plugs from the turf, enabling moisture and nutrients to reach the soil.

Aeration also reduces soil compaction and can reduce thatch. Aeration should be done during cool weather periods -- early spring or fall. "Occasionally aerating in the spring can bring weed seeds to the surface," Landschoot says.

Weed Control

Crabgrass can be controlled with pre-emergence herbicides in early to mid-spring. Broadleaf weeds, which include dandelions and ground ivy, are controlled with specific herbicides that should be applied when the weeds are actively growing in late spring or early fall. "It's important to identify which weeds are present and chose the herbicide best suited to controlling it," Landschoot says.

Diseases and insects

"Turfgrass diseases can occur at any time of the year," Landschoot explains. "Get an early and accurate diagnosis, because it can be difficult to control diseases once they've gone beyond early stages of development."

Insects

Most insect problems occur from late spring to early fall.

Japanese beetle grubs feed on turfgrass roots in May and June and again in late August, September and early October. "The best time to control grubs is late summer, when they are small and tend to feed near the soil surface," Landschoot says.

Insects that feed on leaves and stems, such as cinch bugs and sod webworms, are prevalent in June, July and August. Planting or overseeding resistant grasses and watering drought-stressed lawns may help alleviate insect damage.

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EDITORS: To contact Peter Landschoot, please call 814-863-1017.

Contacts: John Wall jtw3@psu.edu 814-863-2719 814-865-1068 fax