Growing healthy tomato plants requires fertile, healthy soil full of available nutrients. Tomatoes grow rapidly, requiring a wide range of elemental nutrients to thrive. Depending on your location, the natural ground soil can be imperfect, requiring a boost from fertilizer.
Fertilizers come in a variety of formats, each having an intended use. Since tomato plants are so popular, there are several fertilizer products designed specifically for them.
First, I’d like to go over the importance of keeping soil healthy and alive. This is often enough to feed a garden throughout the season with no fertilizer at all! Then, I will go through several of the best fertilizers for tomato plants and where to buy them.
In this article (skip ahead):
- Building healthy soil
- About fertilizer grades (NPK)
- Best growth-stage fertilizers
- Best fruiting stage fertilizers
Soil is where all of the magic happens to keep your plants growing strong and healthy. In nature, soil is never sterile, but is instead full of beneficial bacteria and fungus that work symbiotically with plant roots.
This diverse environment full of microorganisms is known as the root microbiome or rhizosphere (see more). If you are planting in a raised bed or a flat garden plot, your focus should be on nurturing this ecosystem!
Not only will it improve the nutrient content of your soil, it will also help the tomato plants absorb them more efficiently. Living soil can also improve moisture retention which is crucial for getting healthy tomato harvests.
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How To Create Living Soil For Tomatoes
There are a number of methods that home gardeners use to keep the soil active and alive. Even compacted, dead soil can be brought back to a healthy state, so don’t be discouraged!
Here are several tactics that I recommend adopting to improve your soil’s health:
- Add compost or compost tea. The quickest method for nurturing soil back to life is by adding organic compost each year before planting. Composting is easy, and it can dramatically improve your harvests and soil health in as little as 1 year! If you have the space, you can easily compost at home. Otherwise, there are several sources for high-quality compost either online or from a local landscaping business.
- Stop tilling. Tilling disturbs the rhizosphere, causing the important ecosystem to become fractured and damaged. Instead of turning over the soil every year, I recommend using a garden fork to gently aerate the soil. This practice is much gentler, keeping the soil’s structure intact while also loosening the soil for planting.
- Add organic matter. Compost is one form of organic matter, but there are several others that can help as well. Some other options are decomposed chicken or cow manure, fermented alfalfa pellets, and sawdust. Amend the soil with organic matter at in early spring or late fall to allow the microorganisms to recover and colonize.
- Keep the land covered. Protecting the soil during summer is key. Having large, open patches of uncovered soil can lead to dehydration and soil erosion. Plant your tomatoes and other plants at an appropriate spacing to keep the soil shaded. You can also plant ground cover crops to keep the soil active.
- Avoid drought. The goal here is similar to keeping the land covered. Allowing your garden soil to dry out completely can kill off beneficial bacteria, as they need water to survive. Water your tomatoes evenly to keep the soil healthy (and to also avoid cracked tomatoes).
- Always have something planted. When the season is coming to an end, your garden may be left bare. Instead of this, plant a cheap cover crop to keep living root systems in the soil. This keeps the rhizosphere active and happy, and also generates nutrients for the following season!
In essence, your tomato plant’s roots are responsible for absorbing nutrients and water to fuel the growth above ground. If the soil is ‘dead,’ the plants will struggle to absorb nutrients, even if they are present.
If you start focusing on soil health now, amending it each year, your tomato plants with grow effortlessly. Better yet, you may not need to apply nearly as much fertilizer for your tomatoes!
Major Nutrients and Plant Stages
First, I’d like to provide a basic understanding of fertilizer grades and how to know what to look for. NPK refers to the 3 major nutrients required for plant growth. They refer to the following:
Nitrogen (N). Nitrogen is required to produce healthy leafy growth. High nitrogen fertilizers help tomatoes build strong branches and produce lots of foliage.
Phosphorus (P). Phosphorus is required for healthy blooms and fruits. This becomes more important during the flowering and fruiting stages of tomato growth.
Potassium (K). Potassium helps plants move water around the plant and encourages healthy immune response.
Fertilizers are always labeled with 3 numbers that refer to these nutrients. The numbers indicate the percentage concentration of each nutrient in the fertilizer. For example, you may see 5-5-5 printed on the packaging of a fertilizer.
Organic fertilizers will typically have lower numbers, while chemical fertilizers can be highly concentrated. We prefer organic, natural sources of nutrition for better tasting and healthier produce.
Tomatoes have two major growth stages. First, the plants grow vigorously to a mature size, focusing on branches and leafy growth. Then, the plants switch to fruiting mode, producing flowers and fruits.
Each stage requires different concentrations of the 3 major plant nutrients. For the growth stage, tomatoes need plenty of nitrogen. For this reason, early stage fertilizers should have a higher N number, for example 10-5-5.
For flowering stages, tomatoes will require less nitrogen and more phosphorus and calcium. These two nutrients help form lots of healthy flower buds and fruits. Calcium is particularly important for avoiding blossom end rot.
Growth Stage Tomato Fertilizers
For young tomato plants through to the beginning of flowering, tomatoes need plenty of nitrogen. Here are some recommended early-stage fertilizers for tomato plants.
Miracle-Gro Performance Organics
- Water soluble
- Includes secondary nutrients
- Use for: Growth & fruiting stages
- Buy here
You know this one works because it has a picture of a tomato on the front, right? While Miracle-Gro is better known for chemical fertilizers, their consumer product line now includes organic options.
I have used both the All Purpose and the Edibles versions of Performance Organics with success. The major benefit is that this option includes all necessary nutrients in one easy to apply format.
The fertilizer is high in nitrogen, but also has significant potassium, calcium and other important secondary nutrients. Potassium is great for keeping the plants healthy and free from disease, while calcium helps form healthy fruits.
I also like that this fertilizer is water soluble. I recommend putting it in an empty watering can, adding a bit of water, and then swishing it to dissolve. Then, fill the watering can up the rest of the way and water your tomatoes.
This tomato fertilizer is great for early stage growth, but may have too much nitrogen for the flowering/fruiting stage. If you wanted to use this all season, you should reduce the strength by half once the tomato flowers begin to bloom in mid-summer.
Bat guano is an all natural fertilizer that is high in nitrogen. This is a great option for early stage tomato growth, especially in outdoor beds.
Bat guano fertilizer can be applied in several ways. You can top-dress your garden beds, mix into the soil before transplanting, or steep and apply in a liquid form.
The drawback of bat guano is the lack of calcium, magnesium and other secondary nutrients that tomatoes require. To supplement, you can combine with another fertilizer or add bone meal or seabird guano (for calcium) and epsom salt (for magnesium) during soil amendment.
However, the benefits are that bat guano is 100% all natural. These forms of fertilizer lead to better tasting fruits and healthier plant growth.
Fox Farm Grow Big
Fox Farm is known for their high-quality bagged soil blends. They also sell various fertilizers for both soil and hydroponic gardening. I have used Fox Farm’s main trio of fertilizers for growing tomatoes and peppers with great success.
Grow Big is used the first stage of tomato growth. It has a 6% nitrogen solution and is intended for weekly application. This keeps the plants happy and producing tons of healthy, green foliage.
Tip: Grow Big is a great option to prevent chlorosis – if you have yellow tomato leaves, try an application of this fertilizer.
Espoma Organic Tomato-tone
- High calcium
- Not water soluble (soil amendment)
- Use for: Growth & fruiting stages
- Buy here
Another tomato-specific fertilizer, Tomato-tone is organic and well suited for all growth stages. The gentle 3-4-6 formula is different from the previous fertilizers as it is meant to be used as a pre-planting amendment.
In other words, this fertilizer should be blended into potting mix or raked into the first 3-4″ of your garden beds before transplanting. The grains are not water-soluble, so it can’t be applied via watering.
You can also apply additional Tomato-tone during the grow season by sprinkling the recommended amount around the base of your plants. The nutrients will then be slow-released over the following weeks during irrigation.
This fertilizer also contains high levels of calcium to help prevent blossom end rot. This condition is extremely common on tomatoes, and is caused entirely by a calcium deficiency.
Note: Tomato-tone is a great year round fertilizer option. Nitrogen is not too high for the fruiting stage, with plenty of calcium and phosphorus.
Fruiting Stage Tomato Fertilizers
Once your tomato plants begin to produce flowers and fruits, you must change your feeding regimen. The plants will still require some nitrogen, but much less. These fertilizers provide more phosphorus and calcium for healthy fruits.
Seabird guano is an all-natural source of high phosphorus and calcium. This particular blend has 11% phosphorus and 20% calcium. These levels are perfect for fruit formation and preventing blossom end rot.
Just like bat guano, seabird guano can be applied by mixing into soil, or by steeping in water. It can also be applied as a foliar spray during a shaded period of the day.
When tomatoes are full-grown and begin to fruit, nitrogen becomes less important. The plants will likely have all they need in the soil from previous applications. If you do see any yellowing leaves, you can apply a reduced-strength nitrogen fertilizer in addition to the seabird guano.
Fox Farm Tiger Bloom
Although I prefer all organic options, I must admit that this stuff works. Tiger Bloom is the flowering stage fertilizer in Fox Farm’s trio of fertilizers.
The liquid form makes this a simple option that can be prepared quickly and easily. The high phosphorus makes this long-lasting.
The feeding schedule from Fox Farm makes it easy to remember exactly when and how much to feed, (usually weekly).
The only drawback of Tiger Bloom is a lack of calcium. You may may need to look into supplementing calcium with bone meal or seabird guano if you notice a deficiency.
Dr. Earth Organic
This is one option that could be used throughout the entire grow season. Dr. Earth’s Organic fertilizer contains enough nitrogen for healthy leafy growth, plus enough phosphorus and calcium for fruiting.
This formula also comes packed full of beneficial bacteria and mycorrhizae. These are great for forming a healthy living soil from day 1.
It is here under the ‘fruiting stage’ because it is not super-high in nitrogen, but focuses more on the bloom nutrients.
Since it is not water soluble, this fertilizer should be sprinkled around the base of plants before watering. It can also be worked into soil before transplanting in the early spring.
I hope this article helps you decide on a suitable fertilizer for your tomato plants. Whether you are growing in containers or in the ground, fertilizer make a world of different in your harvests. Let me know what you would recommend in the comments below!