Water Your Lawn Before or After Fertilizing? The Ultimate Guide


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If you’re a homeowner, you likely know the endless struggle of keeping your lawn green and growing. Fertilizing your lawn is an essential part of having healthy grass, but it can be challenging to know how and when you should fertilize your lawn and whether or not you should water it when you do.

You should water your lawn a day or two before fertilizing to prepare it for the fertilizer. Once you apply fertilizer to your lawn, give it a light sprinkling to help the fertilizer settle to the soil, then wait roughly 24 hours. The day after fertilizing, give your lawn a deep watering. 

In this article, I’ll discuss the following: 

  • If you need to water your lawn after fertilizing it when using granular or liquid fertilizer.
  • How much water you should use when watering fertilizer in. 
  • How often you should water your lawn.
  • What time of year you should fertilize your lawn.
  • What to do about fertilizing your lawn if it’s raining.
  • Whether or not you can add fertilizer to wet grass. 

Let’s get started before the next storm comes in, shall we?

Should Fertilizer Be Watered In?

If you’re fertilizing your yard for the first time, paying attention to all the steps and rules can feel overwhelming. While this process will become easier to remember the more you do it, you’ll want to get in the habit of appropriately following all the necessary steps. 

Fertilizer should always be watered in to help it break down into the soil and effectively feed your lawn. You can gently water your lawn immediately after fertilizing to ensure that the fertilizer makes it to the soil instead of sitting on the blades of grass, and then deeply water 24 hours later. 

As a general rule, it’s good to thoroughly water your lawn before and after applying fertilizer while allowing time for it to absorb into the soil. You should apply fertilizer to your lawn during its growing cycle when it needs nutrients the most. 

By deeply watering your lawn a few days before applying fertilizer, you can activate it and get it ready to be in a place to absorb the fertilizer.

Photo 50028859 | © Anita Star | Dreamstime.com

A small amount of light rain or gentle misting with your hose is perfectly healthy immediately following fertilizer application because it helps shake the fertilizer down to the soil level. 

Fertilizer left on the grass can sometimes cause fertilizer burn on the blades of grass themselves, which isn’t healthy for your lawn, as your grass needs to absorb the nutrients from the fertilizer through its roots, not its leaves. I’ve written an in-depth article about fertilizer burn and how to fix it. Check it out here, to quickly help your lawn recover.

You can then leave your lawn alone for about 24 hours, allowing the fertilizer adequate time to begin the process of breaking down so that when you water it in, it won’t simply wash it away. 

After about a day of letting your fertilizer sit, during which time you’ll want to keep people or pets from walking on the lawn, you’ll want to water in the fertilizer deeply. Plan to fertilize your lawn a day before heavy rain is expected or manually water your lawn. 

Either way, you’ll want to plan on adding roughly two or three inches (5.08 or 7.62 cm) of water to your lawn to help soak the fertilizer into the soil and prepare your grass for absorption of the nutrients through its root system.

Make sure to always check the labels of your fertilizer for specific instructions. 

While these watering-in techniques are good general guidelines to follow, your fertilizer may have instructions different from this, which you should heed. Following the instructions on your fertilizer label is the best chance you’ll have for success when fertilizing.

Some fertilizers, such as those including weed killer, will often need extra time for the herbicide to work effectively. These fertilizers typically instruct you to wait at least 24 hours before watering your lawn at all, contrary to regular fertilizers encouraging a light watering immediately following application. 

What Time of Day Should I Water in Fertilizer?

If you’ve been researching lawn fertilization, you may have noticed that the time of day you fertilize and water your grass impacts your lawn’s overall health.

You should water in fertilizer early in the morning, just before sunrise. Watering at this time allows enough time for the water to soak in before the sun rises without risking mold or fungal growth.

If you water your lawn in the heat of the day, a lot of the moisture will evaporate before it has a chance to absorb into the soil and adequately permeate your grass. By watering your lawn around sunrise, you’re giving your grass several hours before the sun is directly overhead and the temperatures rise for the water to absorb into the ground. 

Conversely, if you water your grass too late in the day after the sun has begun going down, you run the risk of fungal growth with the combination of warm temperatures and lack of sunlight overnight. 

Although it seems that the time of day you water your grass wouldn’t have that much of an impact on your lawn’s health, it can be the difference between a healthy lawn and one that’s thirsty or moldy.

How Much Water Should You Use When Watering Fertilizer In?

Now that you understand the importance of watering in granular fertilizer and what time of day is best to do it, you may wonder just how much water is needed to effectively water in your fertilizer. 

When watering fertilizer in, you’ll need to wet the top 3” (7.62 cm) of soil. You should water your lawn thoroughly after fertilizing, as this process is necessary to help break down the fertilizer and encourage your grass to absorb the nutrients. 

On average, you only need to water your lawn so that the 1”-2” (2.54 or 5.08 cm) of soil gets wet, but when watering fertilizer in, you want to make sure you can reach the entire root system. 

Grass roots can extend to roughly 3” (7.62 cm) below the soil, so when watering soil in, you’ll need to reach this distance. This process may take upwards of an hour, which is why planning your fertilizing a day before heavy rain to aid the process may be beneficial.

In What Intervals Should You Water Your Lawn?

Besides watering in your fertilizer, grass will need to be watered regularly during its growing season to survive and thrive. 

You should water your lawn once or twice a week in the spring and fall, but ramp up to three or four waterings per week in the summer heat. If it’s a very hot summer or if you’re living in a very hot area, you might need to water your lawn daily in summer.

You’ll typically begin your lawn’s fertilization cycle in the spring and continue through early fall while taking a break during winter. 

Some people choose to apply a slow-release winter fertilizer at the beginning of winter. 

The watering cycle should align with the fertilizing cycle and respond to how hot it gets outside. At the beginning and end of the growing cycle (spring and fall), you should be watering your lawn once or twice a week, making sure that it’s getting about an inch or two of water per week. 

However, as the hotter summer months come, it’s important to respond by giving your lawn more water, which means that you’ll have to switch to watering your lawn about three or four days a week.

Your lawn must get a deep watering each time, so a light misting isn’t going to cut it, and depending on the size of your yard, watering your lawn could take upwards of an hour each time. You may want to install a sprinkler system that you can program to water the correct amount if you live somewhere with very little rainfall to avoid having to do this chore so frequently. 

Consider installing a rain gauge if you live somewhere with decent rainfall, especially during the spring and fall months. These handy instruments will tell you how much rain has fallen, which allows you to adjust your watering accordingly. 

Do You Need To Water Your Lawn After Fertilizing It When Using Liquid Fertilizer?

Now that you know all about fertilizing your lawn with granular fertilizer, you may wonder if the same rules apply when using liquid fertilizer. 

You don’t need to water your lawn after fertilizing it when using liquid fertilizer. Many are water-soluble and are applied as you’re watering with a hose. However, a quick rinse after application could prevent fertilizer burn on grass blades.

Liquid fertilizers are fast-acting and start feeding your grass right away. Because of this, they don’t require the slow breakdown time and deep watering that granular fertilizers do.

However, you’ll still want to deeply water your lawn a few days before you apply the fertilizer to prepare it. To avoid any potential fertilizer burn, gently sprinkle your lawn after application to rinse the grass blades off and settle the fertilizer onto the soil floor.

You can wait two to four hours before rinsing your grass if you’d like to give your fertilizer a little bit of time to absorb into the ground before watering. 

The most important thing to remember when applying any fertilizer is to read the packaging. Different fertilizers have different needs and recommendations, and you’ll have the most success if you follow the instructions on your fertilizer container. 

Do You Need To Water Your Lawn After Fertilizing It When Grasscycling?

Another, more natural, type of fertilizing is grasscycling. Grasscycling is when you leave grass trimmings where they are as you mow your lawn. 

Grasscycling is a naturally occurring fertilizer that doesn’t require additional steps. You don’t have to water your lawn after grasscycling, as you can simply leave the grass clippings where they are instead of raking them up. 

Grasscycling can be both a cost-effective and successful fertilizer and can make up 25% of your lawn’s overall fertilization needs. Grass clippings are especially rich in nitrogen and act as a slow-release fertilizer for your lawn. 

Best of all, there’s no chance your grass will get fertilizer burn.

What Time of Year Should You Fertilize Your Lawn?

Now that you know how to fertilize and water in your lawn correctly, you’ll need to know how to stay on the proper fertilization schedule.

The time of year you should fertilize your lawn is in the late spring and continue through early fall. However, this depends on what type of grass you have and the climate you live in. You only need to fertilize your lawn during the few months leading up to the summer through early fall. 

You’ll need to wait until after the last frost before you begin fertilizing your lawn, as frozen soil won’t absorb the fertilizer, which may lead to fertilizer burn.

Use caution when fertilizing, as overfertilization can have serious adverse effects on your lawn. If your grass grows brown in the hot summer months, don’t attempt to fertilize it, or you may end up killing it altogether.

What Do You Do if It’s About To Rain?

Because fertilizing can be a touchy process, it can be challenging to know if you can trust the elements to help you along. 

If it’s about to rain the same day you apply fertilizer, consider waiting until after it rains. Being aware of upcoming rain is an integral part of the fertilization process. While a small amount of rain can be helpful, a large amount of rain can waste fertilizer. 

The amount of rain that falls and how far from the time of fertilization are essential factors in determining whether or not the rainfall will be a help or hindrance. 

What To Do if It’s Raining Right Now

If it’s currently raining, you can still fertilize your lawn as long as the rainfall is very minimal. In fact, you want to apply fertilizer after a heavy watering to prepare it to absorb the fertilizer. 

But you must be able to apply the fertilizer to your lawn without it getting wet and clumping together. If you can apply the fertilizer without issue, it’s OK to do so in light rain, as it saves you the trouble of having to rinse your lawn after you finish applying the fertilizer.

Use caution when it’s raining, however, as too much rain can quickly wash away your fertilizer, resulting in wasted time and product, as well as adverse environmental implications. 

You should be especially cautious of the rain when fertilizing grassy hills, where there’s a higher risk of the fertilizer washing away. If you’re confident that there’s no chance of heavy rainfall within 24 hours of applying your fertilizer, go ahead and keep your timeline. 

If, however, you’re concerned that heavy rain may occur within 24 hours of applying fertilizer, wait until after the rain passes so the fertilizer will have enough time to break down and soak into the soil before being watered in.

What Happens to Fertilizer if It Doesn’t Rain or It Doesn’t Get Watered In?

Now that you understand how helpful light rain can be to water fertilizer, you may wonder what happens if you don’t water it in manually, and it doesn’t rain soon after. 

If you don’t water in your fertilizer, you run the risk of fertilizer burn, and your fertilizer may just wash away the next time it rains heavily. Watering in is an essential part of the fertilization process and is a requirement for your fertilizer to work effectively.

Part of the reason you should gently cover your lawn in water after you apply your fertilizer is to rinse any residual fertilizer off the blades of grass. Fertilizer is concentrated and needs to be broken down by the water and absorbed by the grass roots. 

Additionally, the fertilizer won’t begin the process of breaking down and absorbing into the soil if it never gets wet, so if you don’t water it in, the fertilizer may wash away in heavy rain. 

Should Fertilizer Be Applied to Wet Grass?

Knowing how important it is for fertilizer to be watered in doesn’t necessarily answer the question of whether or not you can fertilize your lawn when it’s wet.

You can apply fertilizer to wet grass as long as it’s not actively raining heavily. The only time you shouldn’t apply fertilizer to wet grass is if the fertilizer instructions specifically say not to, such as fertilizers with weed killer.

Always remember to follow the instructions laid out by your specific fertilizer, but don’t be afraid to apply fertilizer when your grass is wet if it doesn’t expressly prohibit it. You should, however, be cautious of doing so if you fear it’ll rain heavily within 24 hours or it has just rained heavily, resulting in standing water at the base of your lawn. 

Lars

I am always happy to share all my knowledge about how to keep your garden in good condition and make it special.

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