Fall lawn fertilizer: when to apply it and how much

Why fall is the feeding that counts

Penn State Extension calls late summer, early to mid-September in Pennsylvania, the most important time of year to fertilize cool-season turfgrasses. The feeding helps the lawn recover from drought and heat injury sustained in midsummer. It also arrives when cool-season grasses begin to make and store carbohydrates, which they use for root growth, tolerance of disease and stress, and protection from winter injury.

A late-fall feeding can serve as a replacement for an early spring one. Penn State says it can bring an early and noticeable green-up in spring, often with less leaf growth than a spring feeding. Kansas State says a November feeding is taken up by the roots but not used until the following spring.

When to apply it, by region

There is no single date, because it depends on where you live. These are the dates from the extension services we checked.

• Pennsylvania (Penn State): September 1 to 20, and a late-fall feeding in mid-November in most areas, when leaf growth slows or stops but the soil is not frozen.
• Kansas (K-State): around Labor Day, with aeration, and again in November.
• Illinois (Illinois Extension): August 15 to September 15 in central Illinois, August in northern Illinois and September in southern Illinois. The late-season feeding is late October to early November in northern, November in central and late November in southern Illinois.
• Maryland (University of Maryland): September, and October through November 15 for tall fescue and Kentucky bluegrass. Maryland law bars nitrogen and phosphorus applications from November 15 to March 1.

How much to apply

Illinois Extension suggests about 1 pound of nitrogen per 1,000 square feet for each application, and about 3 pounds per growing season split into two or three applications. Penn State’s sample programs for cool-season lawns call for 1 pound in September and 0.75 to 1 pound in November. Maryland’s chart gives 0.7 to 0.9 pound in each of September and October through November 15 for tall fescue and Kentucky bluegrass, with the low end for quick-release nitrogen and the high end for a product that mixes quick and slow release.

Turn the pounds of nitrogen into bag weight with the first number on the label, the percent nitrogen. This is our own arithmetic: divide the pounds of nitrogen you want by that percent as a decimal. One pound from a 20-0-0 fertilizer is 5 pounds of product per 1,000 square feet, so a 5,000 square foot lawn takes 25 pounds.

Penn State says to use a product with a high share of slow-release nitrogen if you go above 1 pound in late summer, and to rely on slow-release sources for late-fall feeding, which is not recommended on sandy soils with quick-release products because of leaching. It says to apply phosphorus and potassium according to a soil test.

The last feeding: when it is too late

The late-fall feeding is meant for the window when the grass has slowed but the soil is workable. Penn State says not to apply nitrogen to lawns under summer dormancy or on frozen surfaces in winter. If you live where a law sets a date, such as Maryland’s November 15, follow it.

If you missed fall altogether, the University of Maryland lists skipped fall fertilization among the reasons to make its optional spring application.

Warm-season lawns: why not to follow this plan

The University of Maryland says warm-season lawns, zoysia and bermudagrass, are fertilized from late spring into summer, and its chart lists no nitrogen for them in September or October. NC State says to avoid high nitrogen on warm-season grasses in fall or winter, since more disease can follow. Texas A&M AgriLife says not to fertilize bermudagrass in late fall and winter when the lawn is or is becoming dormant.

UF/IFAS says to fertilize only when the lawn is actively growing, from about April through September in north and central Florida, because outside that window the grass is less likely to absorb the nutrients and they may leach into nearby water. Your grass type decides which feeding plan fits.

Weather on feeding day

Texas A&M says not to apply fertilizer if heavy rain is expected within 24 hours. K-State says to water in the fertilizer if rainfall does not occur. Our article on fertilizing before or after rain covers the details.