Extension Communications
Extension 4-H Youth Building
Ames, Iowa 50011-3630
(515) 294-9915
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Extension Communications |
8/2/04
Contacts:
Richard Jauron, Horticulture, (515) 294-1871, rjauron@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033,
jmcguire@iastate.edu
Yard and Garden Column for the week of Aug. 6
Late Summer/Early Fall Lawn Care
By Jennifer Hoyer
Horticulture Extension Intern
Iowa State University Extension
August to September is an ideal time to complete turfgrass maintenance tasks. Proper mowing in late summer and early fall helps maintain a healthy, vigorous lawn. Begin planning now to revive your lawn through aerification, thatch removal, seeding and fertilization.
Mowing
Most Iowa lawns are composed of cool season grasses, such as Kentucky bluegrass,
perennial ryegrass and fine-leaved fescues. These grass species grow best
during cool weather. During the heat of summer, Kentucky bluegrass lawns
should be
mowed at a height of 3 to 3-1/2 inches. As temperatures drop in late summer,
lower the mowing height to 2-1/2 to 3 inches.
When mowing, remove no more than one-third of the total leaf surface at any one time. For example, if the mower is set at 3 inches, mow when the grass reaches 4-1/2 inches in height. Continue mowing until the lawn stops growing in late fall.
Aerification
Turfgrass grown on clay soils and lawn areas that receive heavy foot traffic
can easily become compacted. Core aerification loosens compacted soils, improves
drainage and air movement in the soil and promotes the breakdown of thatch.
Core aerifiers have hollow metal tines that remove plugs of soil from the
lawn. Avoid spike-type aerifiers which have solid tines. These can cause
more compaction.
September is a good time to aerify the lawn. Aerification is most beneficial when the core aerifier removes soil cores that are 2 to 3 inches long. For best results, aerify the lawn when the soil is moist. If the soil is dry, the tines may not be able to penetrate to the proper depth. However, the tines may clog in very wet soils.
Aerifying services are available from professional lawn care companies and the machines are often available at rental companies. After aerification, break up the soil cores by raking or mowing.
Thatch removal
Thatch is a layer of living and dead plant material that forms between the
soil surface and the green foliage. A moderate amount of thatch development
is normal, and even beneficial, in home lawns. Thatch is broken down by microbes
in the soil.
However, lawns with more than one-half inch of thatch can have disease, water, and rooting problems. Excessive thatch formation occurs when the accumulation of organic materials exceeds microbial decomposition.
Vertical mowers and power rakes remove excess thatch by lifting thatch to the soil surface. The debris can then be raked and discarded. These machines are commonly available from rental companies. Dethatching in September gives the turfgrass adequate time to recover before the onset of winter.
Seeding
Mid-August through September is the best time to seed new lawns and repair
bare spots in established lawns. Grass seeds germinate quickly in the warm
soils of late summer. After germination, the cool temperatures of late summer
and early fall promote rapid seedling growth. Additionally, fewer weeds germinate
in late summer, providing less competition for the new grass seedlings. Seeding
should be completed by September 30 to give the lawn time to establish before
going dormant in late fall.
Select high quality grass seed suitable for the site conditions. Kentucky bluegrass is best adapted to sunny areas while fine fescues grow better in shaded conditions. Distribute seed uniformly over the area. Small areas can be seeded by hand. A drop-seeder should be used for large areas. After sowing, rake the area lightly to ensure good seed-to-soil contact. To promote germination, mulch the area with clean, weed-free straw to conserve soil moisture and prevent erosion. The ground should be visible through the straw. Water the area. Keep the seedbed moist with frequent, light applications of water until the grass has germinated. Then, begin to water more deeply, but less frequently. Mow at 2-1/2 to 3 inches when the grass is 3-1/2 to 4 inches tall and continue mowing throughout the fall.
Fertilization
September is a good time to fertilize the lawn. September fertilization promotes
a moderate rate of shoot growth and helps to thicken the turf. Apply one
pound of actual nitrogen per 1,000 square feet.
For additional information, consult the following publications:
* Home Lawn Care: Weed Control (PM 930)
* Turfgrass Management Calendar: Kentucky Bluegrass Lawns (PM 1063)
* Establishing a Lawn from Seed (PM 1072)
* Understanding Thatch in the Home Lawn (PM 1755)
These publications and others are available online at: http://www.extension.iastate.edu/pubs/ga.html or at your local county extension office.
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