Late afternoon or early evening (when there's still light, of course) is the best time of day to apply lawn fertilizer. Applying it in the heat of a scorching afternoon can cause the sun's rays to burn your grass—and when your goal is “lush and green,” burned grass blades simply won't cut it.
Ideal Time to Fertilize
Applying fertilizer (and water) in the afternoon will cause the moisture in the soil that is preventing the lawn from burning to evaporate as the sun beats down on the lawn. It's also important for grass to dry out slightly before the nighttime temperatures.
The right time to apply fertilizer is when the grass is growing more roots than blades. In the Northeast and Northwest, that's usually in the fall. In the South and Southwest, it's in the late spring. So in cooler climes, don't even think about it until Labor Day.
We recommend waiting 24 hours after fertilizing to water your lawn, which will give the fertilizer time to settle. After the 24 hours are up, it's important to give it a good soak—not just a quick spritz with your hose—to activate the fertilizer and help the critical nutrients absorb into the soil.
If there are ponds or heavy rain, it's best to wait until the ground processes the water before applying any type of fertilizer. If there's light rain, it's okay to spread dry granular fertilizer. Rainwater helps incorporate it into the soil.
Why Water After Fertilizing? Watering after fertilizing washes the fertilizer off of the grass blades and into the soil, where it can get to work nourishing your lawn. It's also important because if fertilizer sits too long without being watered in, it can burn the grass.
When is the best time to fertilize a lawn – before or after a rain? Too much rain could wash away the fertilizer before it has a chance to soak into the soil, so plan to fertilize several days before a heavy rain arrives or several days later.
Rain After Fertilizer -- Granular Applications
Granular fertilizer and insecticide applications need to be watered in. This activates the product. Slow-release granular fertilizer is not easily washed away and doesn't dissolve quickly in water. So rain after fertilizer is actually a good thing.
Nitrogen, phosphorus, and potassium take time to absorb into your soil. Doing anything too drastic on your lawn, such as cutting your grass, will disrupt this process. We always suggest to our clients that they wait 24 to 48 hours before mowing their lawn after fertilization.
The goal is to soak your lawn until the soil is moist to a few inches deep. The exact amount of time that this may take will depend upon your lawn and its sprinkler system. On average, it could take around 45 minutes to an hour. Of course, Mother Nature will hopefully also be doing some of the watering work.
During the growing season from spring through fall, your lawn, whether established or newly seeded, will perform best when fed four times, with each feeding applied 2 to 3 months apart.
Generally speaking, you should fertilize your lawn at least twice a year to ensure good overall health and keep your grass looking its greenest. But if you fertilize at the wrong time or over-treat your lawn, you could encourage weed growth, or possibly burn the grass.
The top setting for most mowers gives a cutting height between 3.25 and 4 inches. This is best for your lawn, but at a setting of 4 inches you may sometimes see some “laying-over” of turf blades that some people find undesirable. For this reason, some people prefer to mow at 3 or 3.5 inches.
You just have to be careful about the order: always mow before fertilizing if you want to do both on the same day. Mowing the lawn before fertilization on the same day helps the fertilizer spread more evenly.
Timing: Apply early spring lawn fertilizer once between February and April, when your grass is starting to green up and begin to actively grow (around the time your lawn first needs to be mowed).
Avoid applying fertilizers when plants are dormant or under heat and drought stress. Fertilizers should be incorporated into the soil to prevent losses. If you cannot physically incorporate a fertilizer at this point in the season, it may be best to stick with a water-soluble fertilizer.
The standard recommended time you should wait is between 24 to 48 hours (again, check the specific fertilizer in question for further guidance). Most granular fertilizers also recommend watering the grass to help it absorb the nutrients better, so if you do so, you also need to wait for the grass to be dry.
The best time to water grass after mowing is early morning.
Note that if you mow grass at night, wait until the next morning to give it water. Even if the grass seems dry and needs water, it is safer to wait till early morning.
Will Rain Wash Away Fertilizer? The problem with fertilizing just before heavy rainfall is that the water won't have time to slowly filter down into the ground and deliver the nutrients where they need to go. Instead, it will simply wash your fertilizer into the nearest storm drain.
In fact, it's good! Water helps fertilizer fully absorb into the soil. Mild rain after you fertilize is nothing to worry about. But a downpour, or several days of consistent rain, can be a problem.
Can I fertilize my lawn every 2 weeks? To avoid over-fertilizing, applying a fertilizer every two weeks is not recommended. Fertilizing as often as every two weeks will likely lead to problems such as lawn burn, excessive grass growth, as well as polluted water that can lead to toxic algae growth.
Early morning is the best time of day to fertilize your lawn. Fresh morning dew provides just enough moisture for your grass to absorb the fertilizer.
If you need to apply granular fertilizer to your lawn and the grass is wet, the best thing to do is wait for the grass to dry completely before applying the fertilizer. This will help ensure that the fertilizer is able to properly penetrate the soil and be absorbed by the roots of the grass without causing any damage.
Rain, or watering-in too early, is fine for the grass, but it washes the product off the weed leaves, so the weed killer can't do its job. To be safe, it's best to apply the fertilizer when the weather is sure to be dry for a day or more. Then, simply water-in with sprinklers after 24 hours.