Fertilizer Buying Guide

How do you choose the right fertilizer? There are so many available, like lawn fertilizer, plant fertilizer, as well as weed and feed, it can get confusing. Learn which nutrients and ingredients to look for and what alternatives to consider for a perfect lawn and garden.

Perfect Lawn
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Time To Get Really Green?

Your dream garden and lawn are easy once you know how to feed them properly. After reviewing this Fertilizer Buying Guide, take the first steps to being the envy of your neighbourhood.

Fertilizer Components Three of the elements necessary for lawn and plant growth are oxygen, hydrogen, and carbon. They are available from the environment. Plants also need nutrients that are not as readily available. Nutrients don't stay long in the soil and have to be replenished regularly. Each nutrient plays an important role in plant survival and health. Fertilizer is the means of supplying these micronutrients to satisfy the plants’ needs.

Reading a Fertilizer Label

The three numbers (often called NPK) on a fertilizer package tell you the percentage of the primary nutrients' makeup by weight. These percentages in fertilizer compounds are formulated for everything from asparagus to zinnias. The three main components are:

  • Nitrogen (symbol N) for leaf development and vivid green colour. 
  • Phosphorous (symbol P) for root growth. 
  • Potassium (symbol K) sometimes called potash, for root development and disease resistance. 

For example, a bag marked "16-4-8" contains 16% nitrogen, 4% phosphorous and 8% potassium. The other 72% is usually inert filler material, such as clay pellets or granular limestone. To know how much of each is in the bag, multiply the percentage by the size (weight) of the bag. (Example: a 50-lb. bag of 10-10-10 contains 5 pounds each of nitrogen, phosphorus and potassium). There may also be secondary or minor elements in the formula. Don't feel shortchanged by the presence of the so-called inert material in the fertilizer bag. Its purpose is to help distribute the fertilizer evenly and prevent chemical burn.

Fertilizer Types

Granular Fertilizers

Granular fertilizers are applied dry and must be watered in. Granular fertilizers are easier to control because you can actually see how much fertilizer you are using and where it is being dispersed. They are normally applied by hand or mechanical spreaders.

Liquid Fertilizers

Liquid fertilizers are fast-acting. Since they're quickly absorbed, they require application every 2-3 weeks. Most are concentrates, mixed with water prior to application by hose-end sprayer or watering can.


Quick Release Fertilizers

Quick-release fertilizer typically lasts for 3-4 weeks, depending on the temperature and the amount of rainfall. For general use, these water-soluble nitrogen fertilizers (WSN) are also known as commodity or field grade fertilizers.

Slow Release Fertilizers

There are two main types of slow-release fertilizers, known as water-insoluble nitrogen (WIN), available for specific applications: 

  • Sulfur coated, which lasts for about 8 weeks. 
  • Polymer coated, lasting about 12 weeks. 
Both time estimates may vary depending upon the amount of rainfall.

Plant Foods

Included in the fertilizer family are the general or all-purpose plant foods. In addition to granular or liquid form, they are also available as tablets or spikes.


Plant foods are usually in smaller, more manageable packages for use with houseplants. You will find specially formulated plant foods for indoor plants like African violets, cactus and flowering plants. Generally the formulas are higher in nitrogen for  foliage plants and higher in phosphorus for flowering plants.

Plant foods are also available for specific outdoor plants such as roses and acid-loving plants like rhododendrons. Spikes and tablets offer a clean, convenient way to feed, especially in containers where micronutrients are leached out by watering.

Lawn Fertilizers

Lawns have specific fertilizer requirements, depending on the season and the type of turf/grass you grow. Read the instructions on the package carefully before purchasing lawn food. Lawn fertilizers containing various percentages of nitrogen, phosphorus, and potassium are common lawn foods. Fertilizer combined with pesticides are also widely used to boost lawn colour and stimulate growth.

Weed and Feed

Weed and Feed is a common term which refers to fertilizer that contains weed killer for broadleaf weeds such as dandelions or grassy weeds like crabgrass. Look on the label for a list of weeds that can be treated with the product. The two types are:

 • Pre-emergents, such as those commonly used to prevent crabgrass, are weed killers which must be applied before the weeds germinate. They are ineffective if the weeds are already actively growing. Pre-emergent weed killers are often mixed with fertilizer and are applied early in the season. 

• Post-emergents are contact killers. They are effective only if the weeds are already actively growing. They will not kill weeds that have not yet germinated. 

The timing of application of pre-and post-emergents is critical for success. Applying these products too early or too late is essentially a waste of time. If sowing grass seed is also in your lawn schedule, make sure that there is the proper time interval between applying weed and feed and sowing. Read the package carefully before selecting to be sure which product fits your needs.  

Starter fertilizers and winterizers provide extra phosphorus for root growth. Starter fertilizers are applied to provide a boost to newly seeded lawns. Winterizers are used as a last fall feeding to promote off-season root growth.

Pro Tip

Check out our guide to learn how to get rid of crabgrass.

Organic Alternatives

Non-synthetic organic fertilizers, soil conditioners and soil additives are also widely used. Because they lack some added ingredients to slow the nutrient release, these products may have to be applied more frequently. As with synthetic products, apply properly and with caution. Some of the most commonly used are:

• Green sand — from sedimentary marine deposits. Contains potassium and iron. 

• Blood meal — a byproduct of the meat packing industry. Steamed and dried, it is high in phosphorous. 

• Compost — one of the best all around garden materials for soil improvement.

• Cottonseed meal — a byproduct from cotton processing. This is a good source of nitrogen. 

• Fish emulsion — a fish processing byproduct. Mild, nontoxic, and organic, fish emulsion is good for use with tender plants that may suffer fertilizer burn. Yes, it does smell like fish. 

• Super phosphate — rock phosphate combined with sulfuric acid to produce phosphorus in a form easy for plants to uptake. 

• Manure — for soil conditioning. "Hot" manures such as horse, pig and poultry are high in nitrogen and need composting to prevent burning plants. "Cold" manures like cow, sheep, or rabbit can be added directly to the soil. 

Maximizing Your Fertilizer Use

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