How to Fertilize and Water-In With Rain

adding fertilizer to garden
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Fertilize your lawn properly, and you’ll be on your way to a healthy, dense stand of turf that maintains a deep green color and gives weeds a run for their money. First, choose a fertilizer that gives your grass what it needs, based on a soil test, and is suitable for your climate and the time of year when you are applying it. Next, choose a method for applying the fertilizer; the most common options are discussed here. The final step is watering-in the fertilizer to make sure it feeds the grass plants and doesn't get washed away. This can be done with rain or irrigation.

Using a Broadcast or Rotary Spreader

A broadcast or rotary spreader works well when you’re fertilizing larger lawn areas. Apply fertilizer around the edge of the lawn first, and then start to move back and forth across in an orderly pattern. Overlap application strips slightly to ensure that you cover the whole lawn evenly with fertilizer.

Using a Drop Spreader

Choose a drop spreader for controlled fertilizer distribution. Overlap slightly on each pass to ensure you have adequate coverage. You’ll usually pay more for a drop spreader, but if you’re tending a typical suburban-size lawn, it’s worth the investment.

Using a Handheld Broadcast Spreader

A handheld broadcast spreader works well for fertilizing small lawn areas. Walk evenly and slowly, and be sure to overlap distribution patterns slightly with each pass. A small spreader like this also works really well when you have shady areas in your lawn that require a different fertilizer rate than the sunny sections.


Grasscycling refers to letting grass clippings lie on the lawn after cutting. These clippings can provide up to 25 percent of your lawn’s fertilizer needs, saving you time and money. One hundred pounds of lawn clippings can yield up to three to four pounds of nitrogen, an important component of lawn fertilizers.

You don’t need a specialized mulching mower to grasscycle, although you might want to replace your current mower blade with a mulching blade, which cuts grass into smaller pieces that decompose more quickly. Most new mowers these days are designed for mulching grass clippings.

Watering-In the Fertilizer

All fertilizers should be watered in. This ensures that the product will be washed into the soil and become available to the plant through the roots. It is important to water-in with enough water but not too much. Also, while standard fertilizers can be applied to dry or wet grass and can be watered in immediately, fertilizers with weed killer typically should not be watered in for 24 hours after application.

The best way to water-in is to do it naturally, with rain. Try to time the application of fertilizers to just before an expected rainfall of at least 1/4 inch. Rainfall typically provides good, even coverage over the entire lawn area (except under full trees), which can be difficult to achieve with lawn sprinklers.

However, you should plan to water-in with rain only when the rainfall is expected to be steady and not heavy or intense. Heavy or hard rain can easily flood the grass and wash the fertilizer off of the lawn and into the storm sewer system. From there, it typically gets washed into local waterways and contributes to water pollution.

If rain is not expected, you can certainly water-in fertilizer with an irrigation system or even individual sprinklers. Take care to provide even coverage over the entire lawn, making sure you reach all areas. Fertilizer left on dry grass can burn the leaves (blades).

Watering-In With Weed Killer Fertilizer

"Weed and feed" fertilizers that contain weed killer must stay on the grass longer than standard fertilizers to allow time for the herbicide to be absorbed by the weeds. Typically, you should water the grass just before applying these fertilizers, or apply them in the morning when the grass is still wet with dew. The moisture helps the fertilizer granules stick to the weed leaves.

Do not apply weed killer fertilizer when rain is expected within 24 hours. Rain, or watering-in too early, is ok for the grass, but it washes the product off of 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.