How to Fertilize a Tomato Plant


Tomatoes are prolific producers in most home gardens. One way to ensure a healthy and abundant tomato harvest is to properly fertilize throughout the growing season. Fertilization replenishes the nutrients that the tomato plants require to thrive. Underfertilized plants may wilt, yellow or fail to produce as well as better-fed plants. Both garden and container tomatoes require fertilization, though the amounts and delivery methods differ.

Garden Tomatoes

Step 1

Apply a commercial starter fertilizer to the tomato seedlings immediately after planting to the garden bed. Follow label instructions for application method and rates. Use a starter fertilizer formulated for tomatoes or vegetable gardens.

Step 2

Fertilize a second time when the tomatoes on the plant are 1 to 2 inches in diameter, or when the tomatoes first start forming on cherry and small-fruited varieties. Apply 1 lb. of ammonium nitrate fertilizer or 3 lbs. of 10-10-10 analysis fertilizer per 100-foot row. Work the fertilizer into the soil 6 inches from the plant's base.

Step 3

Water the bed immediately after fertilizing. Watering encourages the fertilizer to leech into the soil and rinses any excess off the tomato plants, preventing fertilizer burn.

Step 4

Fertilize with ammonium nitrate or 10-10-10 analysis fertilizer again three weeks after the last application, using the same method and amount. Fertilize a final time after an additional three weeks.

Container Tomatoes

Step 1

Mix fertilizer in with the soil before planting the tomatoes in the container. Add ½ tbsp. of 10-10-10 analysis slow-release fertilizer per every gallon of soil in the container.

Step 2

Mix a 10-10-10 or 20-20-20 analysis water-soluble fertilizer with water at half the strength recommended on the label. Apply this to the tomatoes when they first begin setting fruit.

Step 3

Fertilize with the soluble fertilizer every two weeks throughout the remainder of the gardening season. Fertilizer leeches out of containers more quickly than in beds, so it must be replenished often.

Tips and Warnings

  • Avoid overfertilizing the tomatoes. More fertilizer is not better, it just leads to root burn and wilting of the plants. If too much nitrogen fertilizer is supplied, tomatoes may produce lush foliage and few to no fruits.

Things You'll Need

  • Starter fertilizer
  • Ammonium nitrate
  • 10-10-10 fertilizer
  • Soluble fertilizer


  • University of Illinois Extension: Tomato
  • Ohio State University: Container Vegetable Gardening
Keywords: fertilizing tomatoes, container tomato care, feeding tomato plants

About this Author

Jenny Harrington has been a freelance writer since 2006. Her published articles have appeared in various print and online publications, including the "Dollar Stretcher." Previously, she owned her own business, selling handmade items online, wholesale and at crafts fairs. Harrington's specialties include small business information, crafting, decorating and gardening.