Demystifying Fertilizer – What Is The Secret?

June 3, 2020
What Is Fertilizer?

The fertilizer department of a garden centre can be a mystifying and overwhelming foray into an unknown world. Well hopefully this blog will ease your frustration and take some of the mystery out of the world of fertilizer!

What Is Fertilizer?

Most plants need nutrients in order to grow and bloom properly.  Three main nutrients are required by plants:  NPK

1. Nitrogen (N) – The first number on a bag or box of fertilizer.  It is essential for leaf development and the green leaf color.  A bag of lawn fertilizer in the spring will have a high first number to encourage new leaf growth and green up your lawn.

2. Phosphorous (P) – The second number.  Primarily known for aiding in root formation but is also responsible for helping plants do the job of flowering and fruiting.

3. Potassium (K)  – The third number.  Also known as potash.  Potassium helps with disease resistance and root and stem development.

Plants also require micronutrients such as boron, magnesium, iron and zinc just to name a few!

As mentioned, there are three numbers on a bag or box of fertilizer.  The numbers represent the percentage of each of the three nutrients in the container.  

For example:  A 50 lb. bag of 10-10-10 fertilizer contains 10% Nitrogen, 10%  Phosphorous and 10% Potassium.  This translates to 5 lb. of each nutrient in the 50 lb. bag.  The rest of the bag is “filler” which can be clay or lime particles.  This filler is necessary as it helps to evenly distribute the fertilizer.  

There are two types or categories of fertilizer; synthetic and organic

Plants cannot distinguish between organic and synthetic nutrients.  But that is where the two types part ways.  

Synthetic Fertilizers

Photo: millionplants.com

Synthetic fertilizers are man-made formulations. They come in various types; granular, liquid and slow-release.   They are usually water soluble and quickly provide plants with nutrients.  Synthetics are convenient and easy to apply but usually require multiple applications per season.  Any nutrients not used by the plants are leached into the water supply and can adversely affect the environment.  Synthetic fertilizers do nothing to enhance the value of the soil but if used properly are beneficial used in hanging baskets, window boxes and container plantings.  These plantings use up nutrients quickly and frequent watering washes any extra nutrient away.  Slow-release fertilizers (osmocote) are tiny pelleted prills .  They can be sulphur-coated which feed for 8 weeks or polymer-coated which feed for 12 weeks.  Slow-release fertilizers are activated by heat and moisture.  Again, I use them in above-ground containers- one application at planting time and you are done for the season!

A note about over- fertilization!  We’ve all been there.  MORE IS NOT BETTER!  It can actually have the opposite desired effect.  Read the label and mix as directed.

Organic Fertilizers

Photo: wonderopolis


Organics are basically soil conditioners and are widely used.  Organic alternatives include blood meal (P), kelp (N), fish emulsion, well- aged manures such as cow, sheep, mushroom and best of all- compost.  Of all the soil amendments compost leads the way in soil improvement and providing plant nutrition.  

This process takes time but if you amend your soil each year with organics and top-dress with compost the gardening rewards are many. 

Photo: Proven Winners

A few suggestions to make life easier shopping for fertilizers.  

Most top quality soils sold have three months worth of plant food mixed in already.  This is also true of tropical plant soils.

Keep fertilizer dry and it will last more than one season.  Do not freeze.

Do not apply fertilizers late in the growing season.  By late, I mean anything past mid August .  This also applies to houseplants.

Mix soil amendments together in a wheel barrow before adding to the garden.  Your back will thank you. 

Tomatoes and roses  in the ground and large containers are heavy feeders.  They use up soil nutrients quickly. 

Visit the manufacturer’s website before shopping.  Our online shopping fertilizer choices will provide you with the lines we carry at Floral Acres.