Like politics, all lawn care in America is local — well, let’s make that regional. But you get the point. Consider the differences in turfgrass growing conditions from Cleveland to Miami to Oklahoma City. Each region is markedly different in seasonal temperatures, precipitation levels, soil types and the dominant turfgrass species most suited to their unique conditions.

In other words, when it comes to fall fertilization, one size does not fit all. Lawn fertility regimes that benefit turfgrass in one region are wasteful and may even harm lawns in another. Also, soils in different regions of the country (even soils within a single region or market) may differ in terms of soil pH and plant-available nutrients such as phosphorus and potassium.

Don’t guess. If you don’t know what’s in the soil, how can you accurately prescribe a fertility program that’s most beneficial to the turfgrass it supports? When in doubt rely on soil tests to show you the way, especially for new or struggling properties coming under your care. Personnel at your county extension office can help you with advice and soil tests. In many cases their services are free.

Read more: Understanding a Soil Test Analysis Report

Now’s the time to fertilize

Let’s start with the birthplace of modern lawn care, the Northeast and Midwest where cool-season grasses such as Kentucky bluegrass, perennial ryegrass and tall fescue dominate residential and commercial properties.

If you can only fertilize these cool-season grasses once a year, do it in September. Turfgrass is recovering from July and August’s high soil temperatures and it’s beginning to store carbohydrate reserves, which help it to resist winter injury and disease, and serve as a source of energy for root and shoot growth the following spring.

Many professional application companies offer two late-season fertilizations. They apply one pound of quick-release nitrogen in late summer or early September and another application of N in late October or November. The mid- to late-fall application delivers better winter color, enhances spring green up and increases plant rooting.

Research at The Ohio State University has shown that root growth of cool-season turfgrass species occurs during the fall after shoot growth has slowed or ceased. This is because roots grow quite well when soil temperatures are between 40 and 65 degrees Fahrenheit, while shoot growth favors temperatures in the 60-75 F degree range. Some root growth will continue as long as the soil remains unfrozen, that research showed.

Look before you treat

Heed the following caveats when making fall applications of fertilizers. If the turfgrass is obviously not growing and likely dead, don’t waste your fall fertilizer. It’s not going to bring the grass back to health. Reseed or sod instead.

Also, don’t apply fertilizer just before you are expecting heavy rains or when the ground is frozen (either in the winter or early spring). Again, you will be wasting money. While most fertilizers require water to infiltrate the soil, a heavy rain can wash away the fertilizer before it enters the soil. When the ground is frozen, granular or liquid fertilizers cannot permeate the soil. Fertilizer will find its way into storm drains or other waterways adding nitrogen and potassium to the water. This can lead to algae blooms and have other negative affects.

Finally, you may encounter lawns with large shady areas where one of several varieties of fine fescue predominates. There are many different cultivars of fescues. You can cut back on the amount of nitrogen fescues receive to perhaps half of what you use on Kentucky bluegrass. Applying no more than 0.50 pound of nitrogen in mid fall is recommended for fine fescues.

Transition zone blues

Maintaining green, lush lawns in the so-called transition zone is a bigger challenge than it is in climates farther north and south. The zone extends through the central part of the country – from northern Maryland westward through the Ohio Valley to Kansas and the Texas Panhandle with its southern boundary dissecting Mississippi, Alabama, Georgia and South Carolina. This region of the country is cold enough in the winter to make it difficult to maintain warm-season species and warm enough in the summer to severely stress cool-season species. No one species is well adapted in this region.

Cool-season species such as bluegrass, fescues and ryegrasses are common in the northern half of the zone, so you can, making adjustments for local conditions, fertilize these lawns as previously suggested.

Tall fescue in particular is common on any residential and commercial properties in the transition zone. Fescues require a medium-level of nitrogen fertility per growing month, but generally respond well to applications of one pound of nitrogen in both September and again in November.

Fertilize only during growth

Warm-season grasses such as bermudagrass, buffalograss and zoysiagrass are found in the more southerly parts of this region.

Bermudagrass is the most common lawn grass in many regions of the Mid-South. It is popular because it is durable and recovers rapidly from wear. Fertilize bermudagrass when it is actively growing from May through August, although applying no more than 0.50 pound N per 1,000 square feet in September four to six months before the first expected frost is beneficial, as well, suggests University of Arkansas extension.

Zoysiagrass grows by both stolons and rhizomes. It goes dormant with the first frost. Do not apply nitrogen to zoysiagrass after the end of August, advises Clemson cooperative extension. By contrast, zoysias.com says that while fertilizer requirements are generally lower for zoysia than many other lawn grasses, they do benefit from a fall application.

Fertilize buffalograss in summer when it is actively growing, one to two pounds annually, suggests Kansas State University. Do not fertilize it in the fall or spring when it is dormant. The grass will not respond and you will be wasting fertilizer.

Centipedegrass is another warm-season grass found on lawns in the South. Like buffalograss it does not require very much fertilizer — one to two pounds N annually while it is actively growing, starting with a half-pound in the spring, reports Clemson extension.

Timing always matters

We come to Florida and the warm coastal regions of the Southeast and Texas where St. Augustine lawns grace residential and commercial properties. Fall fertilization gets tricky depending upon where the St. Augustine lawns are.  Winters in north Florida and other more northerly regions where the grass grows are much colder than south Florida and coastal far southeast Texas that typically have near-tropical winters. Consequently, timing the last fertilization of the season while the grass is still actively growing and before it goes dormant depends on local conditions.

Finally, Florida law prohibits applying more than one pound of nitrogen per 1,000 square feet for any application. Also, many local and regional jurisdictions in the state have strict rules about when and how much fertilizer can be applied to turfgrass. Follow the rules.

America is a land of incredible diversity in terms of geography and climate. Consequently, many different species of turfgrass, each adapted to a particular region, require our care. When it comes to lawn fertilization, and fall fertilization in particular, one size does not fit all.