When and How often to fertilize lawn (Best time & Schedule)

Unless you’re growing a low-maintenance lawn like buffalo or centipede grass, you’ll need to fertilize your lawn to keep it growing strong.

There are many crazy specific fertilizer schedules out there, but less is better when it comes to healthy lawns.

The best schedule for you depends on a few key details: your grass type and species, whether you go with organic or synthetic fertilizer, and how much effort you want to put into it.

Cool-season, warm-season, or transition grasses

All turfgrass species belong to one of 3 types: cool-season grasses, warm-season grasses, or transition grasses. The best time to fertilize your lawn depends on which type of grass you have.

Cool-season grasses

They are found in northern US states and Canada. They grow most vibrantly in the cooler temperatures of spring and fall and go dormant (brown) in the summer heat so they can survive dry heat waves.

They may even stay green during the winter, although that depends on how cold your winters are. Cool-season grasses are usually mixes or blends of different species or varieties.

Warm-season grasses

They are found in the southern US, where the summer temperatures are hot and the winters cool but not frozen. They grow most vibrantly during the heat of the summer and go dormant (brown) in the cooler winter weather.

People who can’t stand a dormant lawn will overseed with a cool-season grass like annual ryegrass, so the lawn keeps some green in the winter, which complicates a fertilizing schedule.

Outside of overseeding with cool-season grass, warm-season grasses are usually a single species and variety rather than a mix.

The most well-known warm-season grass is Bermuda grass, but there are others. Centipede grass is known as grass that will never need a lawn care company.

Transition zones

They are found between these 2 areas, where summer is hot-hot-hot, and the winters are cold-cold-cold, a mix of the north and south. While buffalo grass and little bluestem are amazingly low-maintenance choices, most lawns in the transition are either cool-season or warm-season.

Organic vs. synthetic fertilizer

While you may be tempted to pick up a bag of synthetic fertilizer at your local hardware store, they come with a ton of disadvantages to your lawn, your health, and the environment.

Synthetic fertilizers don’t remain in the soil very long (even slow-release fertilizers), require extra care to avoid nitrogen burn, encourage erosion and soil compaction.

They also rob the soil of organic matter and beneficial microorganisms and have negative health impacts on you, your family and pets, and any aquatic life in your nearby groundwater.

Organic fertilizer will last year-long, won’t cause nitrogen to burn, aerate the soil, prevent erosion, add organic matter and support beneficial microorganisms, and are better for human and environmental health.

Suppose you want a low-maintenance lawn, transition to an organic lawn using organic fertilizers. The transition will require a few years of nurturing, but you’ll love it in the end.

I recommend reading Paul Tukey’s essential guide, The Organic Lawn Care Manual, for a complete schedule for transitioning painlessly to organic.

Leaving grass clippings

Whichever type of fertilizer you go with, you can reduce the amount of fertilizer you need to apply by leaving grass clippings on your lawn. Grass clippings can make up ¼ to ½ of your lawn’s nutrients needs [PDF].

Don’t worry. Leaving grass clippings doesn’t cause thatch buildup. If your lawn soil is somewhat healthy, fresh grass clippings will break down quickly.

If you water your lawn after mowing (or better yet, it rains), the water will push the grass clippings down from sitting on top of your grass to being hidden. They will completely decompose in a couple of weeks.

Why pay for more fertilizer when you can use something that you’ll otherwise just throw away?

How often to fertilize

How often to fertilize depends on whether you go with an organic or synthetic fertilizer. Because they give quick color boosts that don’t last very long, you’ll need to apply synthetic fertilizer much more often.

However, don’t go over 4 applications a year. Then you’re just spending a lot of time and money making your grass grow crazy fast, meaning you have to mow more often, and more nitrogen leaches into waterways, groundwater, and the surrounding environment.

With organic fertilizers, you’ll only need to fertilize once, maybe twice, a year for the best effect.

Best time of day to fertilize

The best time to fertilize is also the best time to mow: between 8 to 10 AM or 4 to 6 PM, although this will depend on weather and water factors. Here are a few guidelines to follow:

High heat and fertilizer don’t mix, especially with cool-season grasses. Asking cool-season grasses to absorb high amounts of nitrogen while surviving heat or drought will not end well for your lawn.

Wait until the grass dries from morning dew or rain before applying fertilizer. Droplets will weigh grass blades down, preventing fertilizers from evenly reaching the soil.

While you can fertilize before a light rain if you’re expecting a big rainstorm, wait. Synthetic fertilizers will wash away before they even have a chance to absorb.

Don’t wait too long in the evening to fertilize, as grass needs time to dry out a bit before the cool nighttime temperatures. Wet grass is more susceptible to fungal diseases.

Only fertilize when the grass is growing, not when it’s gone dormant.

Find out about the ideal time of day for fertilizing plants:

When to fertilize cool-season grasses

The best time to fertilize cool-season grasses is in the spring and fall when they’re growing most vibrantly.

Spring: apply fertilizer after the last frost when the grass thrives again, between April to June, depending on your location.

Fall: apply fertilizer just before the trees drop their leaves, from late August to October, depending on your location. Fertilize well before the first frost date, as you don’t want to encourage your grass to grow in time for frost to kill it. (Since compost is slow-release, it won’t affect the grass as much.)

If you’re using organic fertilizer like compost and only want to fertilize once, fertilize in the fall. The extra compost will help shelter your grass and the soil over the winter.

It also gives the beneficial microorganisms in your grass time over the winter to break down the organic matter into nutrients. This gives your lawn a head-start come spring.

If you’re fertilizing twice a year, apply a light amount of fertilizer in the spring and a heavier fall.

Don’t fertilize in the summer, especially when the grass has gone brown. The grass is fine. Feeding synthetic fertilizer will not make it turn green. Instead, force-feeding it nitrogen when it’s dormant is just going to stress it out — and could even kill your lawn.

When to fertilize warm-season grasses

The best time to fertilize warm-season grasses is between late-spring to late-summer, when these grasses are growing most vibrantly.

March: apply any amendments as required by soil test results and/or compost tea.

Last-spring: fertilize in June. If using synthetic fertilizer, start your 4-to-6 week fertilizer schedule. If using compost, use a lighter top-up, if you choose. Warm-season grass will begin growing actively when soil temperatures reach 65F, which is usually around April.

Late-summer: give one final fertilizer in August while the grass is still growing vibrantly to prepare the winter dormancy grass.

If you’ve overseeded with cool-season grasses, you may need to fertilize once more in November, when they grow more vigorously. If you’ve given your lawn a good compost feeding, though, this might not be necessary.

And if you have centipede grass, you’re in luck! Centipede grass doesn’t like extra nitrogen, so you don’t have to fertilize.

When to fertilize transition grasses

While warm and cool-season grasses are pretty straightforward, transition grasses depend on your specific region and grass variety.

While I listed 2 types of grass as good options for the transition zone as they can handle extreme highs and lows, many established lawns will either be warm or cool-season grasses that require nurturing through the summer or winter.

More people choose the cool-season as it’s easier to nurture cool-season grass through hot summers than warm-season through frigid winters, although changing climates throw a monkey wrench into that.

For the best advice, consult your local university extension office. They have a ton of local info finding the best time for your grass and region.

Buffalo Grass requires very little fertilizer if any. Too much fertilizer can kill it. (It also doesn’t require mowing.)

Blue-stem Grass also requires very little fertilizer, if any. It may be mixed with cool-season fescues, which will keep the lawn green in the cool-season, while blue-stem grass is green (and whimsically blue-ish) in the summer.

For warm-season and cool-season grasses, follow the guidelines above, but be aware that the months may change based on your region’s climate.

How often should the lawn be fertilized?

Conclusion

Fertilizer schedules don’t have to be complicated. If you only take away one guideline, then take away this: only fertilize when your grass is growing.