Fertilizing your tomatoes — What to use and when to use it

Always lots and lots of questions about fertilizing tomatoes…

Do I need to fertilize? What do I use and how often do I fertilize?

The answer is YES. You need to fertilize … Tomato plants are heavy feeders of fertilizer.

Use a liquid fertilizer or a granular fertilizer that dissolves in water to become a liquid and a fertilizer made for tomatoes/vegetables.  

Regarding dry fertilizers that rot and decompose … this takes time … like weeks and sometimes months.  Your tomato season is over before the fertilizer decomposes. Liquids are taken up right away by the plant … like within a day or two.

Kellogg’s Organic Plus Liquid 
miracle gro plant food bag
Miracle-Gro….for vegetables & herbs   

Dissolves in water to become a liquid         

Questions I hear are “My plants don’t seem to be doing that well … they have some yellow leaves, light green foliage … not growing that well … what do I do?”  

Answer—This may mean you need to fertilize. And many people email back that fertilizing did the trick. 

A plant short on fertilizer is not dark green as it should be—it’s generally a lighter green in color with some yellowing of leaves. A plant short on fertilizer in the soil, may draw the fertilizer it needs from its lower leaves on the plant and moving this fertilizer from the lower leaves to the growing tips.This turns the lower leaves yellow. We’re not talking about old plants having produced their tomatoes and now in the process of dying. We’re talking about plants on their way to producing a load of tomatoes.

Many people are using great potting soil that contains fertilizer and says it feeds your tomato for up to like 6 months … but, it’s not enough! Tomato plants are heavy feeders of fertilizer. What to do?  Even if you have great potting soil that says it fertilizes plants for up to 6 months … you need to fertilize your tomatoes.

What kind of fertilizer should I use? Whether you are an organic person or a “who cares” person, “I just want some great tomatoes,” use a liquid fertilizer or a granular fertilizer that dissolves in water to become a liquid. It will come in a straight liquid form in a bottle or in a package where you add water and the granules dissolve and it becomes liquid. The fertilizer package, box or bottle MUST say it’s for TOMATOES and/or VEGETABLES. Don’t be using a lawn fertilizer, etc.

Why use a liquid fertilizer or a bag of granular fertilizer that dissolves in water??  

In short–Your tomato plant absorbs liquid through it roots immediately. 

Dry fertilizers that rot and decompose … this takes weeks and sometimes months … and you need warm soil that activates the microscopic organisms to rot and decompose the soil … with tomatoes and most vegetable gardens, you don’t have that amount of time … they are growing quickly … so use a liquid fertilizer or granules that dissolve in water becoming liquid … your plants will take up the fertilizer right away … within a day or two.  

Generally speaking–a general rule of thumb follows:

The fertilizer used for your tomatoes and vegetable garden should have about equal parts of the following. 

Nitrogen—which is for leafy top growth.

Phosphorus/phosphate–which is for root and fruit production.   

Potassium/Potash–which is for disease resistance and general durability.

Example No. 1: a liquid organic bottle of fertilizer such as Kellogg’s that says 2-2-2, means the bottle contains 2% nitrogen, 2% phosphorus/phosphate and 2% potassium/potash, leaving 94% of the liquid in the bottle as filler.

This is OK and just follow the directions for use. It may say use a couple times a week … follow directions and use a couple times per week.

Example No. 2: a non-organic bag of granular fertilizer that dissolves in water says 18-18-21….it means 18% of the bag is nitrogen, 18% of the bag is phosphorus/phosphate and 21% is potassium/potash leaving 43% as filler.

Again, this is fine. Follow directions on the package. It may say use every 7-14 days. follow directions. 

You will choose either an organic fertilizer—generally made by nature, or a regular man-made fertilizer.

Generally speaking, the man-made fertilizer acts more quickly … as in immediately/instantly.

Below are examples of an organic and of a man-made type fertilizer for tomatoes. 

The liquid organic fertilizer used in the example is from Kellogg. It’s called “Organic Plus” with a label says it’s for fruits and vegetables. The label says 2-2-2 (2% nitrogen, 2% phosphorus/phosphate, 2% potassium/potash).  

Directions say mix 2 tablespoons of the liquid fertilizer with a gallon of water and apply once or twice each week.  

1 tomato plant gets the full gallon each time … it’s as simple as that … just follow the directions.

The next example is a regular fertilizer. “Miracle-Gro water soluble TOMATO plant food.” Label says 18-18-21 (18% nitrogen, 18% phosphorus/ phosphate, 21% potash/potassium). Label says IT’S FOR TOMATOES. 

Reading further it says it’s good for all vegetables. Directions say to mix and dissolve 1½ tablespoons of the fertilizer granules with 1½ gallons of water and apply every 7-14 days. 1 tomato plant gets the full 1½ gallons each time.

Remember: Use a LIQUID fertilizer or like the above Miracle Grow Tomato Food that dissolves in water and becomes liquid. With a liquid or one that dissolves in water, you will see more immediate/instant results as it is almost immediately taken up by the roots … like within 2-3 days your plant will become more dark green and will begin to look a lot healthier. Those with Self-Watering Containers—mix your fertilizer in water and you can pour the mixture on top the soil around the base of the plant or use a funnel and pour down the water fill pipe. Either way works. Sometimes I put 1½ tablespoons of granules or 2 tablespoons of Kellogg’s liquid Organic Plus down each Self-Watering fill pipe then fill with water down the same fill pipe dissolving the granules and/or spreading out the Kellogg’s. As the roots take up water, they will also take up the fertilizer.  

You are welcome to share this information with others—clubs—perhaps share this with your general membership to include those that could not attend the lecture, family, friends, etc. 


Dave Freed “The Tomato Guy”