One of the most critical activities a gardener can perform when growing tomatoes is applying fertilizer. This will give gardeners the tastiest fruit and the most significant volume of tomatoes. However, not everyone knows the proper way to fertilize their tomato plants.
Tomatoes transition through four growing stages: seedling, vegetative, flowering, and fruiting. Depending on your tomato plant’s growth stage, you will apply fertilizer differently.
After years and years of growing thousands of tomatoes in my garden, I’m confident my How-To-Guide will help you. I’ve also compiled a list of the best fertilizers for your tomatoes that have helped me improve all aspects of growing tomatoes. And don’t skip my expert tips!
Seedling Stage Fertilization
Understanding your soil composition is vital before applying fertilizer during the seedling growth stage. A soil test will give you a comprehensive understanding of the nutrients unique to the soil your tomatoes will grow in. After receiving your soil results and understanding the nutrients you need, you can apply a nitrogen-rich fertilizer with a 20-10-10 npk ratio to your tomatoes during the seedling stage.
Instructions
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Mix potting soil with a slow-release organic fertilizer that is rich in nitrogen
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Plant your tomato a gardening container. Fill in the rest of the hole with your potting mix. Water for 15 – 30 seconds
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Sprinkle a small amount of granular slow-release fertilizer 3-4 inches around the base of the plant (avoid fertilizing the stem or leaves of the plant). Water for 15 – 30 seconds after. Repeat 2 – 3 weeks after.
Vegetative Stage Fertilization
As your tomato plants grow, you must transplant them indoors or in a gardening container into your garden. At this point, you will need to fertilize your tomatoes differently, with a 10-20-20 NPK ratio. Throughout this process, you must continue to test your garden soil to ensure it is between a pH of 6.0 and 7.0. This will help prevent over-fertilization that leads to excess vegetation at the expense of fruit formation.
Instructions
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Mix garden soil with a slow-release organic fertilizer that is rich in nitrogen
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Transplant your tomato. Fill the rest of the hole with your garden soil mix. Water for 15 – 30 seconds.
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Apply a liquid fertilizer or water-soluble mix rich in phosphorous around the base of the plant 2 weeks before your tomato plant begins to flower. Water for 15 – 30 seconds after.
Flower Stage Fertilization
As your tomato plants grow and develop flowers, you will need to continue to provide fertilizer with phosphorous, just not at the same ratio as during the vegetative stage. Typically, gardeners will shift to a balanced 10-10-10 NPK ratio fertilizer. Too much or too little fertilizer will prevent flowers from forming fruit.
Instructions
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Apply a quick-release liquid fertilizer or water-soluble mix that contains phosophorous around the base of the plant 2 weeks after your tomato plant begins to flower. Water for 15 – 30 seconds after.
Fruit Fertilization
Once fruit begins to form on their plants, most beginner gardeners make the common mistake of stopping their fertilization process. Applying fertilizer with a 5-10-10 NPK ratio is critical to having the healthiest fruit that can remain on the tomato plant for the longest period.
Instructions
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Apply a liquid fertilizer mix with a higher ratio of phosphorous and potassium around the base of the plant two to three weeks after your tomato plant begins to grow fruit. Water for 15 – 30 seconds after.
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Once fruit begin to grow larger, reduce the liquid fertilizer application to once a month. If leaves are yellow or fruit remain small, apply fertilizer every week until growth improves.
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At the end of the growing season, reduce the liquid fertilizer mix to every 6 weeks if healthy tomatoes remain on the plant. If the plant is not healthy, leaves are wilting, or end of the season rot begins to form on tomatoes then apply the liquid fertilizer mix weekly until you pull the tomato plants out of the ground.
Expert Tips
Several complementary gardening techniques can be applied during fertilization, increasing the likelihood of having a large yield of delicious tomatoes.
Gardeners can apply 1/2 inch of organic mulch around tomato plants when planting/transplanting. This will help conserve moisture, regulate soil temperature, and contribute to the nutrient content of the soil as it breaks down, potentially reducing the need for additional fertilization application.
Another great fertilization technique is to add a 1/2 cup of worm castings around the tomato plant base monthly. This will provide an additional slow-release source of power that will help deliver solid and productive tomato plants.
Not only that but according to the University of California, “worm castings contain rich microbiological colonies that help fight soil-borne plant diseases and repel insects.” It should be noted that this is an excellent complement to fertilizing because it will not lead to excess nutrients that typically hinder flower and fruit formation.
Frequently Asked Questions
No. The above instructions will work on all varieties of tomato plants and cordon and bush tomatoes.
It will depend on the specific fertilizer type you use during fertilization. Always read the instructions on the back of the label. Other factors include plant size, soil type, and growth stage. Too much fertilizer can damage or potentially kill your plant.
It is recommended to fertilize tomato plants in the morning while dew or moisture is still on the ground and top of the soil. This will prevent your plants from scorching by the sun or heat and allow nutrients to penetrate the soil during the day.
Learn More About Tomates
While understanding how to fertilize tomato plants is critical to the success of growing tomatoes, you can check out my other articles about important tomato fertilizer information to help increase the likelihood of success:
- Best Tomato Fertilizers
- Best NPK Ratio for Tomatoes
- 7 Nutrients Tomatoes Need
And you can’t fertilize tomato plants without first learning How to Grow Tomatoes from Seed!
Take Away
Understanding how to fertilize tomatoes during each plant’s growth stage is critical to the plant’s overall health and ability to produce fruit. The tomato plant will grow strong and healthy by applying the correct fertilizing technique during each stage. Expect an abundance of flowers, fruit, and delicious meals ahead.
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