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

What fertilizer is best for tomatoes? Always use a liquid fertilizer or a granular fertilizer that dissolves in water to become a liquid and a fertilizer made for tomatoes/vegetables. Liquids are taken up by the plant almost immediately… As the roots take up water, the roots also take up the fertilizer and immediately deliver to the top.

Do I need to fertilize? The answer is YES. Tomato plants are heavy feeders of fertilizer.

How often do I fertilize tomatoes? Read and follow the directions on your fertilizer package.

There are always lots and lots of questions about fertilizing tomatoes…

Dry type fertilizers that you sprinkle in the soil around the base of the tomato plants must first rot and decompose before the plants can take the nutrients up through their root systems.… this takes time … like weeks and sometimes months for the dry fertilizer to rot and decompose. Your tomato season may be over before the fertilizer decomposes to a point the plants can take it up the nutrients.

Questions I often hear are “My plants don’t seem to be doing that well … some yellow leaves, light green foliage … not growing that well … what do I do?” Answer—it may mean you need to fertilize. And many people email back that fertilizing did the trick.

A plant short on fertilizer 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. In a forest sometimes you see trees with dead branches nearest the ground … a similar thing is happening, the plant is moving nutrients to where the tree needs them most — the growing tips.

We have talked about potting soil and which to use. ome potting soils says it contains fertilizer and feeds your tomato for up to like 6 months … it’s not enough! Some people use great organic potting soils that contains no fertilizers at all. Tomato plants are heavy feeders of fertilizer. Even if you have great potting soil that says it fertilizes plants for up to 6 months … you need to fertilize your tomatoes and begin within the first couple weeks of planting.

What fertilizer should I use? Let’s review. 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. The fertilizer package, box or bottle MUST say it’s for TOMATOES and/or VEGETABLES and HERBS. Don’t be using a lawn fertilizer, etc.

The fertilizer will come in a straight liquid form in a bottle. Or it will come in a package where you add water and the granules dissolve and it becomes liquid (Dissolves in the water like Kool-Aid). Why use a liquid fertilizer or a bag of granular fertilizer that dissolves in water? In short, your tomato plant absorbs liquid nutrients through its roots immediately.

How to choose a fertilizer for tomatoes? You will choose either an organic fertilizer—generally made by nature, or you will choose a regular man-made fertilizer. The man-made fertilizer tends to act more quickly … as in immediately/instantly.

The liquid organic fertilizer in the picture above is from Kellogg’s. It’s called “Organic Plus” with a label says it’s for fruits and vegetables. The label says that the bottle contains 2-2-2 (2% nitrogen, 2% phosphorus / phosphate, 2% potassium / potash). That leaves 94% of the liquid in the bottle as filler. All this adds up to 100% of what’s in the bottle.

Follow directions how often to use. You will make up about a gallon each time—1 tomato plant gets the full gallon each time … it’s as simple as that …don’t be stingy.

miracle gro plant food bag

The non-organic fertilizer in the above picture is Miracle-Gro water soluble plant food for Vegetables and Herbs. It is granular and dissolves in water just like Kool-Aid. Label says 18-18-21 (18% nitrogen, 18% phosphorus/ phosphate, 21% potash/potassium). This means 18% of the bag is nitrogen, 18% of the bag is phosphorus/phosphate and 21% is potassium/potash. That leaves 43% as filler. All adds up to 100% of what’s in the package.

Follow directions how often to use. You will make up about a gallon each time—1 tomato plant gets the full gallon each time.

Fertilizers used for tomatoes and vegetables should contain about equal parts of the following:

  • Nitrogen, for leafy top growth
  • Phosphorus/phosphate, for root and fruit production.
  • Potassium/potash, for disease resistance and general durability.

If you use a fertilizer too rich in nitrogen—the nitrogen number is much higher than the other numbers, the 3 numbers not fairly equal or evenly balanced numbers—you will get too much leafy growth and not enough fruit. When you first plant your tomato plants you can use fertilizer higher in nitrogen a time or 2 in the beginning to get your tomato plant going but then switch to the proper vegetable garden/tomato plant fertilizer.

You are welcome to share this information with others—family, friends and clubs, etc.

Sharing tips helps us be better growers.

Dave Freed / 🍅 the Tomato Guy