Tomato Feeding

Tomato feeding liquid fertilzer.
Feeding tomatoes a dilute 3-3-3 liquid fertilzer.

Tomatoes are heavy feeders. Keep them well fed over the season.

Simple Schedule for Feeding Tomatoes:

  • Seedlings. Give tomato seedlings a balanced fertilizer once a month while they are still in the greenhouse or hothouse. Use a dilute fish emulsion, 3-3-3, or a nitrogen-phosphorus-potassium formula that is similar.
  • Transplanting. When tomatoes are ready to go into the garden, dig a hole as deep as the length of the seedling. Place a layer of aged compost or well-rotted manure at the bottom. Add a handful of bone meal and 1 tablespoon of Epsom salt (which contains magnesium and sulfur to benefit roots). Next add an inch or half inch buffer layer of soil so that the plant’s tender roots do not set directly on the fertilizer. Set the seedling into the hole burying all but the top four branches or leaf sets.
  • Two weeks after transplanting. Side-dress plants: water with compost tea or dilute fish emulsion
  • After first flowers appear. Side-dress plants: water with compost tea or dilute fish emulsion
  • When fruit is the size of a golf ball. Side-dress plants: water with compost tea or dilute fish emulsion.
  • First ripe tomato. Side-dress plants: water with compost tea or dilute fish emulsion.

Best tips on How to Grow Tomatoes.

Fish emulsion you will find at the garden center. Compost tea is easily prepared: place a handful of compost in an old gym sock, tie off the sock, and place it in a container of water until the water turns the color of tea. Your compost tea is ready; it will contain all of the major and minor nutrients found in compost.

A complete organic fertilizer 5-10-10 or 10-10-10 is a good alternative to compost tea or fish emulsion. (A cupful of fertilizer–about a half pound should be enough for 10 plants.) Avoid high nitrogen fertilizers such as urea or ammonium sulfate which will produce tall green plants with little or no fruit.

Side-Dressing Tomatoes:

Side-dressing is easily accomplished: place the fertilizer in a one-inch-deep circular furrow around each plant. The furrow should be 3 or 4 inches away from the stem. Cover the fertilizer with 1 or 2 inches of soil and allow the rain or irrigation to carry the nutrients down into the root zone.

Phosphorus is the most important nutrient to tomatoes. Phosphorus supports root and fruit growth and contributes to good yields and early harvests.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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