When to fertilize in Spring

What fertilizer numbers to use in spring?

a good ratio is 4:0:2:0.5S (Nitrogen, Phosphorus, Potassium, Sulfur) ex. 20-0-10-2.5S

Can you use fall fertilizer in the spring?

Yes, fertilizer is fertilizer, all that matters is the analysis (NPK). Products are marketed for seasons in box stores to sell products.

Does spring fertilizer need to be watered?

All fertilizer should be watered in when possible but isn't a huge issue in cool wet springs. Uncoated urea is the most important fertilizer to water in, especially as temperatures rise.

Spring fertilizer or grass seed first?

Either or is fine. Just avoid high doses of soluble fertilizer to newly emerged seedlings. Stay below 0.75 lb per 1000sq. ft. per application.

Fertilizing your lawn in the spring is an essential part of maintaining healthy and vibrant turf. Proper fertilization provides your lawn with essential nutrients to support lush growth. Spring fertilizer will also help to prevent disease, weeds, and summer drought stress.
Timing is crucial when it comes to fertilizing your lawn, applying fertilizer at the wrong time can lead to poor results and even damage to your turf. Application rates are just as important as timing, too much and you’ll need to mow a lot more. In some cases, excessive fertilizer will encourage disease and insect damage or burn a healthy lawn. It is better to err on the side of caution when fertilizing, better to under-apply than over-apply.
when to fertilize in spring

Spring fertilizer numbers

NPK is an abbreviation that refers to the three primary macronutrients that plants need to grow: nitrogen (N), phosphorus (P), and potassium (K). These nutrients are often included in fertilizers, as they are essential for plant growth and health. Understanding NPK is important for gardeners, farmers, and homeowners as it helps them choose the right fertilizer for their plants
Just because these are primary nutrients does not mean you need to add them all the time or in the same quantities as each other. The NPK ratio on a fertilizer label provides information about the relative amounts of each of these nutrients in the fertilizer. For example, a fertilizer with an NPK ratio of 10-10-10 contains equal amounts of nitrogen, phosphorus, and potassium.

Spring fertilizer types

Soluble fertilizers dissolve easily in water and are quickly absorbed by plants, while insoluble fertilizers do not dissolve easily in water and are released slowly over time. Both types of fertilizers can be either organic or synthetic. In general, synthetic fertilizers are soluble, and organic are insoluble. This may change if synthetic fertilizers are formulated to be slow-release.
When reading the label of fertilizer, anything with an N value greater than 11 will contain synthetic ingredients. The one exception is soluble amino acids which can have an analysis of 18-0-0

First Spring fertilizer application (Late April-May)

The timing of the first fertilizer application in the spring depends on soil temperature. The first application should be made when soil temperatures reach around 10°C to 12°C, typically around late April to early May in Ontario. This is when your lawn starts to actively grow, fertilizing during active growth will benefit your lawn the most.
When selecting a spring fertilizer, it’s beneficial to consider the nitrogen-to-potassium ratio. The nitrogen-to-potassium ratio recommended is a label ratio of 2:1. For the first application, a good start is to apply 0.5 lbs of nitrogen per 1000 square feet and thus, 0.25 lbs of potassium (as K2O). An example of this is 20-0-10.
Added potassium is more beneficial in the spring because soils are cool and potassium is less available. Turf growth is high and so is their need for potassium. Potassium is quickly redistributed into the soil via clippings and microbes will also help to make this nutrient available in warmer soil conditions.

Second Spring fertilizer application (May)

The second fertilizer application should be applied 3 weeks after the first application. This timing allows for the initial fertilizer to be used by the turf, while also allowing a third application before summer. For the second application, a slightly higher nitrogen rate of 0.75 lb per 1000 square feet is recommended.

Third Spring fertilizer application (June)

It’s important to apply smaller applications of fertilizer more frequently instead of all at once. This is why we recommend 3 applications of spring fertilizer. The third application of spring fertilizer should be 0.5-0.75 lbs per 1000 square feet.

Quick and easy lawn fertilization

If you are willing to sacrifice quality for time, you can get away with one spring fertilizer application per year. If you wish to do so, it’s recommended that you apply 0.75-1 lb of slow-release fertilizers from a mix of compost, corn gluten, or biosolids. Supplement this with 0.5-0.75 lb of soluble fertilizer at the same time.
The best time for a single application is mid-May.

Tips for fertilizing a lawn

nice lawn
Use a Rotary Spreader: The best way to apply fertilizer to your lawn is by using a rotary spreader. It allows for even distribution and ensures that the fertilizer is spread uniformly across the lawn. Set the spreader to half output rate and go over your lawn twice in a criss-cross pattern for best results.
Do Not Apply More Than 1 lb of soluble Nitrogen at Once
It is crucial not to over-fertilize your lawn, as it can damage the grass beyond repair. Read the label on your fertilizer to determine the amount of nitrogen it contains, and adjust accordingly.
Do Not Fertilize a Dormant Lawn
A dormant lawn is a lawn that has turned brown or straw-colored due to a lack of water or cold weather. Applying fertilizer to a dormant lawn is a waste of resources since the grass cannot use the nutrients. Wait until the lawn starts growing again before fertilizing.
Cut Fertilizer Amount in Half for Shaded Lawns
Shaded lawns do not need as much fertilizer as lawns in direct sunlight. This is because shaded lawns grow slower than sunny lawns do.
Bagging clippings
By now, most homeowners are aware of the benefits mulching your clippings provide. If you must bag lawn clippings, you should consider increasing your fertilizer applications by 25% to make up for the lost nutrients.
Use this fertilizer calculator.


Knowing the NPK (nitrogen, phosphorus, and potassium) values of fertilizers is important as it helps determine the right fertilizer for your lawn. Applying spring lawn fertilizer at the right time can help promote healthy growth and prevent weed growth. It is better to fertilize in 3 small applications rather than 1 large application as it allows for more even nutrient uptake by the grass and reduces the risk of nutrient runoff or leaching.

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