When to Fertilize Your Lawn

Stake sign in grass that reads "Fertilize Your Lawn"

If you fertilize your lawn at the wrong time of year, you might as well not fertilize it at all. So, what is the right time of year? That depends on your grass type’s growing season. This guide details when to fertilize your lawn, whether you have cool-season or warm-season grass.

Why Should You Fertilize Your Lawn?

Keeping your lawn looking green and fresh can be tricky, especially when it’s exposed to changing temperatures, lawn diseases, pests, and weeds. One way to help your lawn stay healthy is to fertilize it. Here’s what regular fertilization does for your grass:

  • Provides necessary nutrients – A healthy lawn begins with good soil quality, something fertilizer can help you achieve. It replaces and replenishes essential nutrients your lawn needs to look beautiful. The three most important macronutrients are nitrogen (N), phosphorus (P), and potassium (K) – also written as N-P-K.
  • Promotes healthy grass growth – Incorporating fertilizer into your lawn’s diet will promote healthy grass and deep roots. With the necessary nutrients, your lawn will be healthy and stay green for longer. Say goodbye to dry patches, discoloration, and weak grass blades.
  • Maintains a beautiful lawn – Proper fertilization enhances lawn color, density, and overall appearance, contributing to your home’s curb appeal.
  • Prevents weeds – Some fertilizers carry weed-control treatments known as “weed-and-feed.” But the main role of fertilizer is to provide the grass with the tools it needs to grow thick and strong, becoming naturally less susceptible to weed attacks.
  • Creates disease barrier – By definition, lawn diseases trigger a host of problems that can turn your healthy lawn into an eyesore. Regular fertilization makes lawns less disease-prone and more resistant to attacks. Simply put, in case of any stress, your lawn will bounce back much faster.
  • Keeps pests at bay – Pests will have a much harder time attacking a thick and sturdy lawn. Plus, certain fertilizers contain insecticides known to kill pests and prevent infestation.
Map of the United States showing cool-season grass, warm-season grass, and transition zones.
Photo Credit: Juan Rodriguez

When to Fertilize Your Lawn

The first step in knowing when to fertilize is to identify the type of grass growing in your yard.

There are two primary varieties of grass: cool-season and warm-season. Cool-season grasses grow in the country’s northern parts, while warm-season grasses grow in the southern region. A third of the country is in the Transition Zone, where either grass can grow. To see what zone you’re in, look at this USDA hardiness zone map.

When planning a fertilization schedule that works for you, it’s also important to consider soil quality and the local climate. Soil testing determines the nutrient levels in your soil, giving you a starting point for your fertilization plan. Different climates typically impact fertilizer requirements depending on temperature and moisture levels. Regular monitoring and adjusting based on your grass’ needs will contribute to a healthy, thriving lawn you won’t want to leave.

When to Fertilize Cool-Season Grasses

A picture showing growth of cool season grass round the year
Photo Credit: Juan Rodriguez

Cool-season grasses experience their most vigorous growth during the cooler parts of the year, particularly in the spring and fall. During this time, they’re better able to utilize available moisture and nutrients, resulting in lush, silky lawns. These grasses flourish in climates with warm summers and cold winters.

Well-known cool-season types include:

  • Kentucky bluegrass
  • Bentgrass
  • Ryegrass
  • Fine fescue
  • Tall fescue

Avoid feeding your cool-season grass too early, as this will encourage leaf growth but leave the root system weaker and susceptible to damage. Be mindful of soil temperatures, which for cool-season grasses need to be around 55 degrees Fahrenheit for successful fertilization.

Follow up with a winterizing variety six to eight weeks after your late fall fertilizer application. This is best done when your cool-season grass is still green, but has stopped growing (air temperatures will usually be in the 50 to 55 degree Fahrenheit range). Winterizing fertilizer is full of potassium and phosphorus to help your grass maintain strong roots in winter but low in nitrogen to prevent leaf growth during this time. 

Consider this fertilization schedule for cool-season grasses:

  • 1st round – Early spring (mid-April)
  • 2nd round – Early fall (September) 
  • 3rd round – Late fall (mid to late October)

When to Fertilize Warm-Season Grasses

Photo Credit: Juan Rodriguez

Warm-season grasses grow best in places with warm year-round temperatures. They’ll often turn brown in the winter, which means they’ve gone dormant. Depending on where you live, winter dormancy usually lasts about three to five months.

Types of warm-season grasses include:

  • Bahiagrass
  • Zoysiagrass
  • Bermudagrass
  • Buffalograss
  • Centipedegrass
  • St. Augustinegrass
  • Carpetgrass

Feed your warm-season grass every six to eight weeks during its active growth season (see above). Start your first round when soil temperatures have been holding steady at 65 degrees Fahrenheit for a few weeks. 

When it’s time for your summer feeding (the most important feeding time for warm-season grasses), adding some organic fertilizer to your regular fertilizer is a good idea. Whether you add manure, bone meal, or compost, this boost of nutrients can better prepare your warm-season grass for winter dormancy.

Consider this fertilization schedule for warm-season grasses:

  • 1st round – Mid to late spring (around April)
  • 2nd round – Early summer (June)
  • 3rd round – Early fall (September)

Tips and Tricks for Successful Fertilization

Regular fertilization promotes robust grass growth and increases resilience against pests and diseases. Consider these practical tips and tricks when fertilizing your own lawn:

Photo Credit: Ivan-balvan / Canva Pro / License
  1. Soil test – Begin by testing your soil to understand its exact nutrient composition and pH levels. This can guide you in selecting the right fertilizer and determining the proper application amounts. To do this, gather samples from several locations in your yard, trying various depths for optimal results (up to 12 inches). Send your samples to the nearest testing lab for detailed analysis, or contact a local Department of Agriculture extension office.
  2. Choose the right fertilizer – Select a fertilizer with the appropriate balance of macronutrients: nitrogen, phosphorus, and potassium – all based on your soil test results. Read the instructions carefully before starting. Fertilizer ingredients may change, so don’t assume you already know what your bag of goodies contains.
  3. Timing matters – Fertilize during the growing season for your grass type. Avoid fertilizing during extreme weather conditions (storms, rainfall, drought) or dormant periods. Choose a clear, warm (not hot), wind- and rain-free day to apply the fertilizer for best results. Your fertilizer will stay put, and you won’t risk sunburn or heat stroke.
a illustraton of aeration
Photo Credit: Juan Rodriguez
  1. Dethatch and aerate – Excessive thatch can impede the movement of air, water, and nutrients to the grassroots. Dethatching before fertilization removes this barrier, allowing the fertilizer to reach the soil and roots more effectively. Follow up with core or spike aeration to maximize the movement of necessary components for grass growth.
  2. Tackle pest and weed control – If you have a weed or pest infestation, apply herbicides or pesticides first, allowing enough time for the products to take effect before applying fertilizer. Don’t forget that some pests and weeds are more active during specific times of the year, so plan your treatments correctly. Then, follow up with fertilizer during a suitable period for your grass type.
  3. Give an even application – If you’re applying granular fertilizer, use a rotary spreader (ideal for larger lawns) or a drop spreader (ideal for smaller turfs). Compost is best applied using your hands to ensure an even, hassle-free application. Organic fertilizers sometimes get stuck in the spreader, which is why manual labor is recommended. If you go for liquid fertilizer, use a lawn sprayer to coat the turfgrass evenly. Some fertilizer bottles can be directly attached to a hose to simplify the process.
  4. Follow recommended application rates – The right amount of fertilizer can mean the difference between a drab and fab lawn. Adhere to the recommended application rates written on the fertilizer label. Over-fertilization can harm your lawn and the surrounding environment. 
  5. Water after application – Water the lawn immediately after fertilizing with granules to activate the fertilizer. This minimizes the risk of burning your grass and promotes better nutrient absorption. If you apply liquid fertilizer, wait between 12 and 24 hours before watering, giving the fertilizer time to dry and settle.
Black mower in half-mowed lawn sorrounded by shrubs.
Photo Credit: MariuszBlach / Canva Pro / License
  1. Mowing considerations – Mowing your lawn before fertilization can be a good practice, as it removes the top layer of grass, allowing the fertilizer to reach the soil faster. Avoid mowing immediately after applying fertilizer to allow time for the nutrients to penetrate the soil. Also, keep your mower blades sharp to prevent stress on the grass.
  2. Environmental considerations – Be mindful of environmental factors. Avoid fertilizing near bodies of water and choose slow-release fertilizers to minimize nutrient runoff. 
Sunday - LawnStarter Block

FAQ About When to Fertilize Your Lawn

How long should I keep pets off my lawn after fertilization?

Keep your lawn pet-free for about 24-48 hours. It’ll give the fertilizer plenty of time to sink into the soil and keep your pets safe from any potential effects of the fertilizer. If ingested, commercial fertilizer may lead to allergic reactions, while organic fertilizer has been known to cause indigestion and bowel obstruction.

What happens if I over-fertilize my lawn?

Too much of a good thing is a bad thing. Too much fertilizer can weaken your lawn and leave it vulnerable to pests and diseases – the exact things you want to prevent. Not to mention that excess liquid fertilizer can contaminate nearby waterways and put people at risk.

How should I store my fertilizer?

When it comes to fertilizer storage, a good rule of thumb is following the directions provided by the manufacturer. These usually include:

  • Storing the fertilizer in a dry, cool, secure location – preferably in its original container.
  • Keeping it away from pets, children, or any other critters that may gain access to the storage space.
  • Making sure the fertilizer is kept away from flammable products.

Get Top-Notch Help From a Pro

By now, you know that timing is a critical factor in achieving a thriving outdoor space. Aligning your fertilization schedule with your grass’ natural cycles and other lawn care practices will result in proper growth and sustained vigor against hot summer temperatures and winter challenges.

Whether you’re a DIY-er or prefer hiring a local lawn care pro to give your lawn the nutrients it deserves, fertilization is a must if you dream of a thriving outdoor space for years to come. 

Main Photo Credit: Shutterstock

Andie Ioo

Andie Ioo

In my free time, I enjoy traveling with my husband, sports, trying out new recipes, reading, and watching reruns of '90s TV shows. As a way to relax and decompress, I enjoy landscaping around my little yard and DIY home projects.