When and How Much to Water Lawn Fertilizer

Brendon Willis
Rotary spreader fertilizing lawn


So you just had your lawn fertilized and you’re wanting to know: How much do I water after my lawn has been fertilized? Or, when is it safe to water my lawn after fertilizing?

Before we take a deep-dive, let this be a general fact about watering your lawn, especially in regards to fertilizer: If you’re not watering your lawn on a routine basis, it doesn’t make sense to fertilize your lawn. Fertilizers are made effective by a growing turfgrass.

If your lawn is weak or dormant due to a lack of water on a normal basis, fertilizing isn’t going to do much for your lawn.

Don’t let this article mislead you into thinking that you ONLY need to water before or after fertilizer.

Are you sure it’s fertilizer? The difference between fertilizer and herbicides.

In lawn care, terminology sometimes has different meanings depending on the people you talk to and parts of the country. It’s important to understand the difference between fertilizer and herbicides before we tackle the watering question.

Fertilizers and herbicides can both be applied with the same methods or with different methods. Spraying or pushing a spreader around the lawn is a way to know the method of application, but not the type of application.

Many people refer to anything that is applied to the lawn as “lawn fertilizing” and that may not be true.

Let’s look at the type of application here.

Herbicides – Post-emergent, pre-emergent, weed killers & weed preventers

  • Herbicides are the products applied to your lawn to attack or prevent weeds from growing in your lawn.
  • Herbicides are typically applied via a blanket application or by spot-treating only the affected areas. A blanket application is an evenly applied layer of herbicides spread across your entire lawn. These are especially common with pre-emergent weed control.
  • We have a separate article written to address the specifics of when and how much to water after a pre-emergent treatment. It’s important to get this right or you could be negating the application altogether.

Fertilizers – Nutrients and elements required for a healthy lawn

  • Fertilizers are applied to a lawn to encourage a deep green color, root and canopy vigor, and ultimately the best version of your turf.
  • Fertilizers are either a slow or quick release and are activated by water or by absorbing into the foliage. (more on that in the next section)
  • Fertilizers are almost always applied via a blanket application to the entire lawn area.

Fertilizer and Herbicide Blends

There are also products commonly used that contain fertilizers and herbicides. These are great products as they can save you a lot of labor – addressing multiple issues with a single pass across the lawn.

The Types of Fertilizers Affected by Watering

To adequately understand how much and when to water after fertilizing, it’s important to understand the method of fertilization you received. The following covers the two primary methods of spreading fertilizer and how to identify what type you have received.

The two types of fertilizers are:

  • Granular fertilizers
  • Liquid fertilizers

Granular Fertilizer

Granular fertilizer is applied with either a rotary spreader or a drop spreader. So, if the product was applied by pushing a piece of equipment around the lawn, it was probably a granular treatment.

Drop Spreader vs Rotary Spreader lawn fertilizer
Drop-type spreader (left) vs rotary-type spreader (right)

You can sometimes find the small granules (aka prills) on pavement next to grass after a treatment. This is a granular fertilizer treatment. Those millions of tiny prills are broken down by water and make their way into the soil.

Granular fertilizer is systemic. This means it must be watered into the soil to be taken up by the roots of your turf grass.

For this reason, granular fertilizers (and granular herbicides) will absolutely be ineffective until they receive adequate and ongoing water.

Liquid Fertilizer

Liquid fertilizer is sprayed onto your lawn using a hose-end attachment (for DIY) or a tank, pump, hose, and applicating gun (by a professional.)

Willis Lawn technician applying liquid fertilizer

Liquid fertilizers are a contact product. This means the nutrients are taken up by the plant through the foliage rather than the roots. This differs from granular products in that liquid products do not require watering the lawn afterwards for them to be taken up.

This does not mean, however, that you don’t need to water your lawn before and after. There are also some good guidelines to follow for when to water after a liquid fertilizer treatment. We’ll cover that next.

When to Water After Fertilizing

Watering before and after fertilizer treatments is key to ensure the product does not go to waste. Now, when you are safe to water depends on what type of application you received. (See above for types.)

When to Water After Granular Fertilizer Application

A granular fertilizer application can be watered in immediately after application. In fact, the product could even be applied in the rain if it were functionally possible! Granular fertilizer is not activated unless it receives moisture and needs to receive normal watering for the plants to take up the fertilizer from the soil.

When to Water After Liquid Fertilizer Application

Liquid fertilizer is taken up by the leaf of your turfgrass and needs to remain on the leaves for at least a few hours to be adequately taken up by the plant. Generally, waiting 12-24 hours before watering is perfectly fine and will ensure the nutrients are taken up completely. However, you should resume normal watering no more than 24 hours after the application.

How Much and How Long to Water After Fertilizer

Watering to the appropriate levels after a fertilizer application is important. Too much and you can have run-off and diluted products. Too little and the fertilizer will just sit on the very surface of the ground and will not provide ideal conditions for the grass to take up the nutrients.

Assuming your watering schedule and amounts are set correctly for your lawn, simply resume your normal watering schedule after fertilizing. To understand how much and for how long you should be watering your lawn, check out our article on how to water your lawn.

If you have heavy clay soils or steep slopes it will be easy to accidentally create run-off water during watering cycles.

Water Run-off Consequences

If you are having a lot of excess water running off into the streets, drives, or sidewalks it is important to try and reduce this. When water is running across the surface, it can displace the fertilizer and create areas of low and high fertility. Both of which are not ideal.

Additionally, if the fertilizer has iron in it and it runs onto a hard surface, the iron will actually cause rust stains which can be very difficult to remove.

Rust on driveway caused by iron fertilizer
Rust from iron fertilizer after it got wet. To prevent, always blow fertilizer off pavement and do not over-water causing run-off.

Sprinkler System or Hose and Sprinkler

Are you using an underground installed sprinkler system or are you watering by hand? It’s important to note that underground systems are far more efficient at evenly applying water to your lawn. if you’re using a hose and sprinkler you will want to pay close attention to how much water is going down to avoid run-off.

Watering After Herbicide Weed Treatments

For information on watering after an herbicide treatment, check out our separate article here.

What Time of Day to Water After Fertilizing

You can water in your fertilizer at any time. Generally speaking, watering in the early morning just as the sun comes up is ideal. This ensures the lawn is irrigated well prior to the heat of the day, but allows the grass canopy to dry out during the day which reduces the likelihood of disease.


Generally speaking, just keep watering your lawn like you normally do! If you don’t know whether you received granular, liquid, fertilizer, or herbicides, just waiting 24 hours is an easy way to be safe no matter what you received. Happy watering!

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