According to the popular 1960’s song, “To everything there is a season—a time to plant, a time to reap.” Perhaps, if Pete Seeger had been a landscape contractor, he would have written, “A time to plant and a time to fertilize.” And if Seeger had been a landscape contractor, given only one season to fertilize, he would have chosen the fall.

Why would he choose the fall?

The answer is quite simple. Of all the seasons, fall is the best time of the year for feeding your lawn because this is the time, just before it goes dormant, for the turf to store nutrients to sustain it over the cold winter months.

In the spring, when the weather turns nice, a good feeding will bring the turf out of dormancy and give your lawn a fresh bounce. In late spring or early summer, lawns will need another feeding to sustain their health. Once the summer season begins and temperatures heat up, you can give your lawn a rest, since cool season grasses don’t grow that quickly in the summer.

But come the fall, everything changes.

“The hormonal balance of a plant shifts during the course of the growing season,” says Gary Neyman of Lebanon Turf, Lebanon, Pennsylvania. “In the spring, the balance is tipped toward promoting top growth, so you don’t want to over-fertilize. In the fall, the balance changes to promote more root growth and storing carbohydrates, so if you fertilize any time of year, fall is the best.”

Fall fertilization replenishes the nutrient supply that was used up over the summer months and gives roots a healthy start, resulting in a healthier, thicker lawn the following spring. Well-fed plants have increased shoot density, improved fall, winter, and spring root growth, and enhanced storage of energy reserves within the turf plant.

Cooler temperatures and shorter days mean that fertilizer applied in the fall aids the photosynthetic production of carbohydrates. These carbohydrates are stored until the following growing season, and then provide the energy source for turfgrasses to recuperate from winter stresses.

David Piper, area manager in northern California for BEST/ Simplot Professional Products, Boise, Idaho, looks at fall fertilization as the winter hardiness nutrition season.

“By helping roots grow before winter sets in, you are ensuring that the lawn will germinate quicker in the spring and become more resistant to disease and drought,” Piper says. “In areas where the temperature is cold enough to freeze the soil, fertilizer applications need to be timed so that the nutrients are available to the plants before the freeze and after the thaw.”

Another advantage to fall fertilization is that weed problems are usually less severe come the spring. September and October are the best months to control perennial broadleaf weeds like dandelions and clover. As weeds prepare for winter, they pull nutrients and starches from their leaves into their roots. They also draw herbicides into their root systems in the process, thus more effectively killing the weed. During September, grasses grow rapidly in the cool fall weather, and with less competition from germinating weeds will quickly fill in the bare spots created after the weeds die.

Another advantage to fall fertilization is that lawns which are well fed at this time of year will tolerate heat and drought better the following summer, because the grass plant produces more root mass and a deeper root system. A good fall fertilizer will also strengthen the grass, so that you won’t need to fertilize as much the next spring.

Now that you’ve been convinced that fall is the best time to fertilize, the next step is to decide the best fall fertilizers to apply.

How to read the numbers

Fertilizer formula is represented by three numbers, such as 5-10-5. The first number represents Nitrogen (N), which helps make plants green and is a key component of chlorophyll and promotes lawn blade and foliage growth. The second number stands for Phosphorus (K), which aids in seeding development, cell building, and root growth. The third number indicates the amount of Potassium (P), which assists in forming starches and proteins that helps plants resist disease and environmental stress and promotes cell function and absorption of trace elements.

When it comes to fall fertilization, the critical ingredient is slow release nitrogen. Nitrogen is a key element to overall plant health; however, it also dissipates very quickly through the soil. This is fine most of the year, but to keep nitrogen feeding plant roots throughout the winter, slow release nitrogen is necessary because it dispenses the nutrient in a controlled, steady manner, ensuring that more of it is absorbed by the plant. It will also aid in photosynthesis, allowing the plants to stay greener a bit longer, extending the green season.

“Slow-release nitrogen fertilizers are especially important for the first fall application,” says Neyman. “When you start noticing that temperatures are going down, you’ll want to use a product that has 34 to 40 percent slow-release nitrogen content. You still have some pretty warm days and you want that application to last into November.”

Steve Crowe, owner of Sunshine Landscaping Company in Cherry Valley, Massachusetts, puts down - to one-pound of nitrogen per thousand square feet in September and October. “We use a 24-5-12 slow-release fertilizer mix that allows the nitrogen to break down over time and provides an extended feeding to the grass.”

According to the calendar, fall begins on September 21, but when it comes to fertilizing, fall can begin as early as the first of September and extend through November 1, depending on climate conditions.

A good rule of thumb to determine when to begin the fall fertilization process is to schedule the application in conjunction with your other services.

“About the time you’re ready to put away your mowing equipment is a good time to start,” says Neyman. “At that stage, you don’t have a lot of top growth. As long as the soil temperatures are warm enough for the plant to continue to grow, it will do a good job of storing carbohydrates and might actually last until the spring, when the turf starts to wake up.”

In the Sunbelt states, where overseeding is a common practice, as the turf plant begins to germinate, a good feeding will help encourage its growth. Although temperatures won’t necessarily drop below freezing, warm season grasses will still feel the effects of seasonal changes as the length of the day becomes shorter. Like humans, sunlight—as well as temperature—has a big effect on a plant’s overall health.

“If you’re going to overseed, fall is an excellent time to fertilize,” says Piper. “The reason is that you still have the warm soil temperatures from the summer and the cooler air temperatures, so it’s ideal for seed and root growth.”

Application of fertilizers in the fall can also be of great benefit to established landscapes. With proper use of selected fertilizers and application timing, improved cold hardiness of plant material can be encouraged. Proper fall fertilization can also supply the plants with a reserve of nutrients, which will be drawn upon during the following spring awakening. Fall is also the best time to put in a new lawn.

Planting a new lawn may take up to 21 days for the seeds to germinate, depending on the weather.

However, once the seed germinates and becomes young seedlings, a good feeding will give the grass plant the balanced nutrients it requires to thrive.

As you begin cutting the lawn, the young seedlings will begin to mature. But once the cold weather comes, the plant will go dormant and hibernate through the winter. As spring approaches and the weather warms up, you begin to cut the grass and these young grass plants are not seedlings anymore. The plants continue to grow and with each mowing they mature and grow stronger, giving them a better chance to survive the heat of the following summer.

Turfgrass isn’t the only plant material that needs fall fertilization to promote healthy rejuvenation in the spring. Flowers, shrubs and trees will benefit from a healthy dose of fertilizer scattered around the roots and cultivated into the soil. The nutrients will still be in the soil come spring when plants start to grow, resulting in healthy plants with an abundance of flowers.

The basic goals of fall fertilizing are to promote strong root growth, maintain a continuous feeding of nutrients and produce a healthy landscape once the winter chill has passed. Without proper fertilization in the fall, come the spring Seeger may be asking, “Where have all the flowers gone?”