Fall lawn plantings

Work with nature, plant in the Fall

By: Sandy Feather 2006
Penn State Extension

Q. We have an older lawn that is in sad shape. We would like to know if it is worth repairing, or should we just start over with our lawn? Also, what is the best time to renovate or start new lawns?

A. Fall is the best time to undertake lawn renovation, overseeding jobs and installation of new lawns. Air temperatures are cooler and less stressful to our cool-season turfgrasses, while soil temperatures are warm enough for rapid seed germination and root development. There is far less weed pressure on fall lawn seedings because most weed seeds are "programmed" to germinate in spring.

Besides, a frost will kill many tender weed seedlings without harming grass seed or seedlings. Fall is also a great time to get lawn weed problems under control, especially tough-to-kill perennial weeds such as ground ivy.

FIRST: What's wrong with the lawn?

The first step is to determine what is wrong with the lawn. Lawns go downhill for many reasons, including:

  • improper mowing
  • soil pH (acidity/alkalinity) too high or too low
  • lack of or improper fertilization
  • lack of or improper irrigation
  • too much shade
  • competition from tree roots
  • turfgrass species not adapted to the site
  • heavy thatch layer
  • soil compaction
  • poor drainage
  • insect or disease problems
  • the weeds are winning

A good place to start is with a soil test. Inadequate (or excessive) fertilization can limit turf growth. A soil test will tell you what type of fertilization program is required. It will also tell you what you have to do to get your soil pH into the optimum range of 6.5 to 7.0 that most turfgrasses prefer. Soil test kits are available from your local Penn State Cooperative Extension office.

Proper mowing methods

Mowing practices greatly determine the quality of turfgrass. If you allow your lawn to grow too long, then cut it short, you are not doing it any favors. Most species of turfgrass should be cut at a height of 2 to 3 inches. The longer the grass, the more extensive its root system.

If you do not water your lawn, drought years past and present have probably taken their toll. Deep infrequent watering during hot, dry weather is important to maintain a healthy lawn. Deep watering encourages the turf to develop a deeper, more extensive root system. Conversely, frequent shallow watering encourages a shallow root system that is stressed during droughts.


Use a sprinkler or an irrigation system to apply 1 to 2 inches of water weekly to your lawn if we are not receiving any rain. This is best applied in one long, deep soaking session. Our clay soils can absorb only about 1/2 inch of water an hour, so it should take two hours of watering to apply an inch of water.

well watered lawn

To measure how long to run your sprinkler or irrigation system, take a flat-bottomed container such as a coffee can and mark off half-inch increments. Place the can where it will be hit by the water, and time how long it takes to gather a half-inch of water. (You may want to place several cans because your sprinkler may not distribute the water evenly.) Then run your sprinkler twice as long.

You may need to apply water even more slowly to steep slopes to avoid wasting it to runoff. It is best to water in the morning. If you water during the heat of the day, too much water is lost to evaporation; if you water at night, the grass stays wet too long and may be more likely to have disease problems.

Species of Grass

Most grass species prefer full sun. If your lawn is heavily shaded, you may need to remove or limb up some of the trees to allow more sun to penetrate. You may also wish to overseed with fine fescues such as creeping red fescue, hard fescue or Chewings fescue. They are the most shade-tolerant species of turfgrass adapted to our climate. The newer turf-type tall fescues perform reasonably well in shade, too.

Also, trees compete with turf for water and nutrients. Turf grown under such conditions should be watered more frequently and fertilized at a heavier rate than turf that does not have such competition. Often, shade-tolerant groundcovers such as barrenwort (Epimedium spp.), ferns, Allegheny foamflower (Tiarella cordifolia), pachysandra or creeping myrtle (Vinca minor) are better than grass in such a situation.



Old Lawns

Older lawns frequently have thick thatch layers. Thatch is a tangled mat of organic matter that accumulates between the soil surface and the grass. Just as we slough off dead skin cells that are replaced by new ones, turfgrass plants slough off dead roots and stems. When these accumulate faster than they break down, a thick thatch layer can build up. How quickly thatch accumulates depends on:

  • The variety of grass in your lawn. Kentucky bluegrass and creeping red fescue spread by underground stems (rhizomes) and tend to build up thatch faster than bunch-type grasses such as perennial ryegrass, turf-type tall fescue and Chewings or hard fescue.
  • The pH of your soil. Soil-dwelling microbes that break thatch down are inactive when the pH falls below 6.5.
  • Mowing practices. Letting your grass grow long, then cutting it short will create more dead roots and stems that end up adding to the thatch layer. Also, leaving very long grass clippings on the lawn on a regular basis will cause thatch to build up. However, a properly used mulching mower does not contribute to the thatch layer because it cuts the clippings into very fine pieces that break down quickly.
  • Over-fertilization. Too much fertilizer causes the grass to grow more quickly than normal and also speeds up the process of sloughing off dead stems and roots, which contribute to thatch build-up.
  • Compacted soil prevents the roots from penetrating deeply. Shallow roots dry out and die faster and add to your thatch woes.

A little bit of thatch, say a half-inch or so, is actually helpful. It acts like a mulch to conserve water, moderate soil temperature and shade out germinating weed seeds.

A heavier thatch layer becomes a breeding ground for disease and insect problems and interferes with treating root feeding insect problems, such as white grubs.

thatch profile

Up to 2 inches of thatch can be removed with a power dethatcher, often available at tool rental shops. Or hire a lawn service to do it.

Run the power dethatcher in one direction, then again in the perpendicular direction. It is important that the tines get through the grass and thatch layer and down into the soil. A properly dethatched lawn should make you want to cry because it is so badly torn up. Overseeding will help it recover.

Dethatching should be done in fall only so that your lawn has ample time to recover. There are limitations to what dethatching can accomplish. If you have a thatch layer more than 2 inches thick, consider starting a new lawn.


Q: I have had better success planting grass in the fall than in the spring. Is there any validity to that, or should it not matter when I seed my lawn?

A: Fall is the BEST time to establish a new lawn for many reasons. First of all, soil temperatures are warm, which creates a favorable environment for seed germination, as well as root growth and establishment. Root growth continues until soil temperature falls below 40 degrees.

Reasons Why

Air temperatures tend to be cooler in fall, which is much less stressful for tender grass seedlings. The cool-season grasses typically grown in our climate perform best in the cooler weather of spring and fall. They generally stay green through much of the winter but will go dormant during hot, dry summer weather unless provided with supplemental irrigation.

Fall-planted lawns have fall, winter and spring to become established before facing the stress of summer heat and drought. If you start a new lawn in the spring, you must be prepared to water most of the summer for it to become well established.

Pressure from Weeds

Finally, there is much less weed pressure on a fall lawn seedling than there is in the spring. Weed seeds are genetically programmed to germinate when they have the best chance to survive and perpetuate the species. For the vast majority of weeds, that is spring.

Although you often see commercial landscape companies seeding new lawns late into the fall, it is best to have your seeding done by Oct. 15th in Pennsylvania.


Carpenter Ants

Chinch Bugs

Crane Flies


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