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Please Feed the Grass!

Reasons To Fertilize Your Lawn


  To live, plants must carry on photosynthesis, a process that requires sunlight, oxygen, water, and some nutrients. Sunlight and oxygen are taken from the atmosphere. Water and nutrients must be taken in through the roots and transferred to the leaves to aid in the photosynthetic process.

  Without all of the building blocks that it needs—the grass will struggle to look like the lush green lawn of our dreams. Plants that are well-fed grow to be healthier and more beautiful, but they are also more productive and more resistant to poor weather conditions and disease.

  As elements in the soil become depleted when they are used up by the growing grass, they are not replenished naturally in an urban ecosystem—they need to be added back into the soil. 

  Fertilizers will supplement the Nitrogen, Phosphorus, and Potassium that the grass needs in large amounts to grow healthy. Plants that grow in unfertilized soil are often deficient in nutrients, they will often grow more slowly and smaller than plants that are getting their nutritional needs met.

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Fertilizer Basics

  In order to understand the nutrients in lawn fertilizer, you simply have to know that the 3 numbers you see standing out, each one separated by a dash, are the primary plant nutrients:


(N) Nitrogen – (P) Phosphorus – (K) Potassium

  They are usually the first ones to be lacking from the soil, and the ones needed the most by plants. Plants use large amounts of them for their growth and survival, but they can also leach from the soil naturally due to the weather, especially during rainy seasons or prolonged hot weather.
  As they are needed in large amounts for healthy plant growth, these three nutrients are called MACROnutrients. Macronutrients are the main elements that the plants consume daily in order to perform and maintain the process of photosynthesis.


Be careful not use too much!

Excessive amounts of nitrogen will burn the grass, damaging the plant tissue and leaving patches of dead grass on your lawn. Always read the packaging label of the products you’re using and follow the instructions carefully.

Nitrogen (N)—it’s what has your grass looking so green!
Nitrogen is a component of chlorophyll and crucial for photosynthesis. Without enough nitrogen plant growth is stunted and leaves become yellowed; a visible sign of nitrogen deficiency is when the grass loses its emerald-green colouring, becoming a lighter, almost yellow-green colour, with a slower growth rate.

More nitrogen = more foliage, which is exactly what a lush green lawn needs.

Phosphorus (P)—it is required for plant growth and can be found in every living plant cell.

It promotes root growth, developing large, deep root systems with better resistance to dry spells. If there is a phosphorus deficiency the grass will have insufficient root mass to reach water and nutrients with its weaker root system.

Potassium (K)—the symbol “K” comes from the Latin name for the element, “kalium”. This element is responsible for making the grass more resilient—able to withstand extreme cold and drought, and resistant to disease. Potassium not only helps the plant handle stress, but also to regulate processes that use available nitrogen. This means that it is needed by the plant to assist nitrogen in bringing about the “greenness” in the grass, which it does by helping with the photosynthetic process.

  The grass needs it throughout the entire growing season, but during the fall, the application of potassium to your lawn goes to help it survive the harsh winter weather conditions. Many fall fertilizers have an increased amount of potassium in the blend, and they are often labeled as “winterizers”.

  Higher levels of potassium will enhance the ability of the grass to tolerate a wide array of environmental stressors, which includes cold damage. These fertilizers will boost the potassium in the soil before winter sets in, which will be helping the grass to break down, absorb, and retain the nutrients that it needs, strengthening the cell walls and fortifying root systems.

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  It’s important to note that carbon (C), hydrogen (H), and oxygen (O) are also crucial elements that the plants need for survival, however, they can be found in abundance from the air and from water.

Additionally, there are 3 more essential nutrients, however, plants require them in much smaller amounts. These SECONDARY nutrients are:

•       Calcium (Ca), which helps bind organic and inorganic particles and improves soil structure. It is a key component in the growth and development of plant cell walls;

•       Magnesium (Mg) contributes to the green coloring of plants. This metallic element is found in chlorophyll and helps the plants to process sunlight—without it they cannot photosynthesize;

•       Sulphur (S) is a component to many proteins, and it contributes to the production of amino acids, enzymes, and vitamins. Plants need it for their growth and for the formation of seeds.

Elements that are needed in tiny amounts are called MICROnutrients, and they are: zinc (Zn), boron (B), manganese (Mn), iron (Fe), molybdenum (Mo), chlorine (Cl), copper (Cu).

These are also sometimes referred to as “trace elements”.

N-P-K ratio:
  The ratio that the macronutrients come in will vary between packages of fertilizer based on the time of year, on how you want your plants to grow, and on the type of plants to be fertilized—the sequence on the label will always be N-P-K, in that order.

Understanding the numbers:
  Due to being combined with inert materials, chemical fertilizers have their potency gauged by the % of their total weight.

  A fertilizer with the N-P-K ratio of 20-10-15 on the label means that it will contain 20% nitrogen, 10% phosphorus, and 15% potassium with the remaining amounts being made up of micronutrients and inert materials. These percentages of nitrogen, phosphorus, and potassium are for the elements in the forms of N, P2O5 and K2O, as they are in standard fertilizers.


The most important thing you can do when using any fertilizer is to carefully read and follow the directions on the product label!

Application rate.
“More” does not equal “better” with fertilizers.

Over-feeding the grass with too much fertilizer at once is a disservice to your lawn: the high concentration of nutrients will be too potent, resulting in damaged grass. For optimal results schedule the fertilizer application for your lawn once every 6-8 weeks starting in the spring, and this will also depend on your lawn’s requirements and how much time you are able dedicate to lawn maintenance. It is important to find the right balance for your lawn—too little fertilizer will not be enough for the grass to be healthy and vibrant; too much will damage your lawn.


Knowing how much fertilizer to use means finding the application rate. This rate is based on the amount of nitrogen (N) in pounds (lbs) recommended for every 1000 square feet of lawn. Nitrogen is not the only nutrient to consider, but generally the nutrient that fertilizer application is based around.

Because of the varying concentration of nitrogen in each fertilizer formula, every fertilizer will need a different application rate. It often takes a few applications to get used to the needs of your particular lawn, it’s OK if you don’t get it right the first time as long as you don’t burn the grass.


Most cool-season grasses require about 2-6 lbs of nitrogen per 1000 square feet of lawn annually for their optimal health. Fescue grasses will usually need less than bluegrass.

Separate the full amount of annual nitrogen into a few applications throughout the year for best results. The commonly suggested rate is 1 pound of nitrogen per 1000 square feet for every fertilizer application, but make sure you read the label of the product you are using as they will often have specific instructions, and make adjustments for your lawn as necessary when you begin to see how the grass is affected.



Please note: while buying in bulk saves you money, fertilizers will “go stale” during storage; they change their potency due to the fluctuating temperatures and humidity from nitrogen evaporation if the bag is left open or poorly sealed for a long time. They need to be stored in a cool, dry area.


Nitrogen is very important for cool-season grasses in the fall—it sets up the grass with the nutrients it needs to flourish in the spring. Some would even suggest that for cool-season grasses, up to 75% of the total annual nitrogen required should be applied during the fall.

Green Talks

Interestingly, there is a point at which the grass reaches its peak or the “maximum greenness” that it can get, so any extra nitrogen that it receives goes only to quicken its growth—which means having to mow it more often. You’ll know how often you need to fertilize if you pay attention to the grass.

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Pictured are nitrogen burns from dog urine on the lawn. Be careful when applying fertilizer to avoid your entire sod in patches like these.

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Schedule of Fertilizer Application:
For the best results with cool-season grasses, you should fertilize lightly in the spring and the heaviest in the fall. If fertilizing only once per year, it would be most beneficial to apply it late summer, or in the fall, ideally after the last mow of the year.


Fertilizing every 6-8 weeks will yield the healthiest and greenest grass, it will be better able to withstand extreme weather, recover more quickly from foot traffic, and it will be more resistant to disease.

Following the “every 6-8 weeks” schedule will have you fertilize approximately 5 times throughout the year:


Fertilizer dissolves with water, so it is best applied to moistened soil (watered a day or two ahead, and given enough time for the grass leaves to dry completely before applying fertilizer) so that the granules begin to dissolve right away and get absorbed quickly. Water the lawn again after application or apply the fertilizer just before a rainy day, but not such heavy rains that it causes the fertilizer to run off.

  When applying fertilizer in the early spring, check that the soil temperature is warm enough for the fertilizer to work.      You can check the soil temperature with a soil temperature tester (you can get it on Amazon) look for the soil to have reached at least 10°C before you fertilize your lawn, it would be wasteful to apply fertilizer before it can be absorbed adequately.

The morning or late afternoon are ideal times to apply fertilizer, and when weather conditions are mild. It shouldn’t be applied during the hottest time of the day, and don’t use it when there is a drought or extended hot weather spell as it might burn the grass.



If the soil in your lawn is very compacted and the water sits on the surface for a while before it drains away, use a liquid fertilizer to avoid burning the grass—fertilizer granules can become a concentrated solution when they dissolve in the standing water, which makes them too potent and causes damage to the grass tissues.

Fertilizer Forms
  Fertilizers are sold as dry granules or concentrate applied in liquid forms.

  The granules are easiest to use because you simply distribute them over the grass and water well. They are easily applied with a drop spreader that can be set at a certain rate that ensures you get even coverage. Plus, the wheel marks in the grass left by the previous pass of the spreader provides convenient guidelines. The granules don't start working until they gradually dissolve and enter the soil with water.


  Concentrates can be either liquid or water-soluble crystals that dissolve in water.Miracle Gro is a popular example of crystal that is applied with a special fixture that fits on the end of your garden hose. You fill its reservoir with crystals and water away. Liquid concentrates work the same way using similar proportioner devices you can buy at the garden center.

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  The problem with liquid concentrates is they are difficult to distribute evenly on the lawn. You can't tell where you've sprayed before, or how much you've sprayed. Lawns are real tattlers because they show light and dark color changes when fertilizers are applied unevenly.

Other things to be aware of when fertilizing:

•  The total amount of fertilizer you need to be calculated using ONLY the lawn area of your yard. DO NOT include areas that are covered by patios, walkways, driveways, sidewalks, garden beds, etc.
•  Fertilizer requirements for your grass will also depend on how much sunlight and water it is receiving, how much traffic it needs to repair from, not just what type of grass you have.

•  It’s possible for grass to grow too lush. If it gets too much nitrogen leading to excessive growth there is the potential for thatch (a dense layer of mixed roots and shoots near the soil surface, thatch is made up of old dead grass and live grass, and can block air and water), which can lead to a higher risk of diseases, among other problems.
•  Keep fertilizers off of areas where the rain might carry them away into storm drains or into rivers, lakes, or other water sources, as fertilizer can be a pollutant.
•  The best time for an annual application of fertilizer is in late summer or early fall if you are only feeding the grass once a year in a low-maintenance approach.

Lawn fertilizer basics.

Wet grass

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