The Best Tomato Plant Fertilizer

Tomatoes give you a healthy dose of vitamin C.

Growing tomatoes is an easy, low-cost way to enjoy a homegrown harvest. The most popular plants in the summer garden, these warm-weather vegetables require full sun, frequent watering and nutrient-rich soil to thrive. Tomato plants also are heavy feeders, needing steady doses of fertilizer during the growing season.

At Planting Time

When you prepare the soil for your tomatoes, the best fertilizer to incorporate is a slow-release, complete formula such as an 8-32-16 or 6-24-24. Once the young plants are in the soil, water them with a starter solution. These solutions are widely available at garden centers and nurseries, or you can make your own by mixing 1 lb. of 8-8-8 fertilizer into 10 gallons of water, or 3 tbsp. per gallon. Use 1 cup of the solution for each tomato plant.

Mid-Season

After the plants have set their fruit, and every week or two thereafter, sidedress with 2 tbsp. per plant of an 8-8-8 or 10-10-10 fertilizer. Tomatoes grown in clay soil will need to be fertilized less often than those grown in sandy soil. The Texas A&M University Extension warns that if you are using a fertilizer high in nitrogen, such as ammonium nitrate or sulfate, reduce the rate to 1 tbsp. per plant.

Additions

If your tomatoes suffer from blossom-end rot, a soft decaying spot on the bottom of the fruits, add a calcium source such as agricultural gypsum or limestone when the flowers first open. If a soil test shows a deficiency in magnesium, sprinkle a handful of Epsom salts around each plant, then water thoroughly. When choosing a fertilizer for your tomato, look for a formula low in nitrogen, high in phosphorous and medium to high in potassium, according to the University of Missouri extension. If your formula is high in nitrogen, it will cause the plants to produce more foliage and branches than fruit.

How to Apply

When sidedressing tomatoes, keep the fertilizer at least 4 inches from the plants' stems. Work it well into the soil to avoid fertilizer burn. Liquid fertilizers can be applied through a drip system, while foliar applications are sprayed or poured directly onto plants' leaves. Liquid and foliar formulas will need to be applied more frequently than slow-release formulas.

References

• University of Missouri Extension: Growing Home Garden Tomatoes; David H. Trinklein; April 2010
• North Carolina State University: Growing Tomatoes for Home Use; Larry Bass; December 1991
• Cornell University: Diagnosing Tomato Problems; Helene Dillard, et al.
• Texas A&M Aggie Horticulture: Tomato, Part I