Late Summer – Early Fall Lawn Care

Late Summer – Early Fall (think September 1-15) is an optimal grass management time for lawns. As the days start to lengthen and cool, grass begins to wake up at the end of the summer dormant and root shedding period. A root growth phase begins that must happen prior to top growth. This becomes one of the most important times to fertilize grass; feeding these new roots. Proper fertilization or soil nutrition is important in maintaining a healthy lawn that resists environmental stress, including competition with weeds and moss and drought stress. Turf fertilization practices for the entire year are built around what you do in the fall. Apply fertilizer in early to mid September to promote regrowth from summer stress. Another application in November is important in keeping the grass competitive with moss through the winter. Use a slow release fertilizer so that you don’t promote a big flush of growth. Fertilize again in early June so that the grass has the nutrients it needs to grow at a moderate rate through the summer stress period. If you want to maintain a lawn of moderate quality, a minimum of three fertilizations through the year is needed. Mow the lawn frequently, removing no more than a third of the plant at each mowing.

In general, you should apply no more than one pound of actual fertilizer nitrogen per 1000 square feet at a time. If the fertilizer analysis is 24-6-12, it contains 24% nitrogen. To apply 1 pound of N per 1000 square feet, you need to apply 4.2 pounds of fertilizer (1 ÷ 0.24 = 4.2). Return clippings (grasscycle) when you mow to recycle nutrients into the lawn.

Many Pacific Northwest lawns have begun to degrade into a clumpy, coarse looking lawn by the fifth year after establishment due to poor fertilization, watering, mowing and overseeding practices. Mid-September to October 15th is an excellent time to overseed the lawn. Since many lawns are a perennial ryegrass-fescue mix, choose a top quality fescue-perennial ryegrass blend for overseeding to avoid a postage stamp appearance in your lawn.

Ciscoe Morris’ recommended overseed practices include:

Important: Soil must be moist but not soggy. If September is hot and dry, may delay up to October 15th.

1. Mow lawn as short as possible to about ¾” mower height. (Only mow to low height if dethatching will be undertaken, but not if only aerification is going to be done.)
2. Remove thatch if over ½” thick (spade up wedge of turf and measure thatch layer). Use rented power rake and dethatch in perpendicular directions. Rake up.
3. Aerate with rented hollow-tine aerator, also in both directions. Mow with rotary mower to disperse soil plugs or not mow.
4. Take up sod from high and low spots, adjust grade with native soil, and replace sod.
5. Optional: top dress with coarse top soil not to exceed ½.”
6. Overseed with 50-50 mix of fine leafed fescue and turf-type perennial ryegrass at rate of 2 lb. seed per 1000 sq. ft. Note: Always use certified seed.
7. Fertilize with lawn starter fertilizer at rate of 1 lb. actual nitrogen (N) per 1000 sq. ft.
8. Lightly rake surface.
9. Go over lawn with roller. Seed must be in contact with soil to germinate.
10. Gently water seed and fertilizer. Soil surface must be kept moist until seed germinates (may need 6 waterings a day in warm weather) and through next 3 mowings.
11. Mow whenever grass is 1/3 taller than recommended height.

David Ridle (DavidR@www.skagitfarmers.com)
Agricultural Products & Services Consultant