For the healthiest plants, you'll want to find a fertilizer that has nitrogen, phosphorous, and potassium, expert gardeners say.
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If you like to grow your own fruits and vegetables, tomatoes are a delicious and versatile choice that can thrive in both huge gardens or on small balconies. Despite the fruit's popularity, tomatoes can be challenging to grow as the heavy feeders require constant nutrition and regular fertilization to produce well. "Like many herbaceous plants, tomatoes need nitrogen, phosphorus, potassium, potash, calcium, and magnesium, along with other trace minerals to grow and fruit successfully," says gardener and tomato growing expert Emma Biggs. To get those necessary nutrients, tomato plants need to be fertilized consistently during their growing season. Ahead, exactly when and how to administer tomato fertilizer, as well as guidance on which type will produce the best harvest.

Key Properties of Tomato Fertilizer 

Tomato plants need three main nutrients from fertilizer—nitrogen, phosphorus, and potassium—as well as some other trace elements. Most fertilizers are a combination of those three components; the packaging will indicate the percentage of each. For example, if there's an equal ratio of nitrogen, phosphorus, and potassium, the fertilizer may be labeled as 10-10-10; if more nitrogen is present, it may appear as 15-10-10. To know how much of each nutrient your plant needs, Michelle Hawks, the lead horticulturist at Reynolda Gardens, recommends having your soil tested. This will gauge the levels of each element in your soil, as well as its pH, which Hawks says should be around six to seven for a tomato plant. Knowing which nutrients your soil needs more or less of will inform you on the specific number series to look for when purchasing plant food. 

ripe tomatoes growing on vine
Credit: Jed Share/Kaoru Share / Getty Images

Types of Tomato Fertilizer 

According to Biggs, the variety of fertilizer you use is a personal choice. "I've tried lots of different fertilizers myself over the years," she says. "That has led me to believe that no single product is best for everyone, and the best way to find out what works for you is to experiment." With that being said, there are a few common types of formulas that you'll come across during your tomato journey. Foliar spray is a type of fertilizer that's diluted in water and sprayed directly onto your plant's leaves. Biggs says it's best to apply this type in the morning. There's also liquid, or dissolvable, iterations. This variety should be mixed with water following the instructions on the packaging and poured at the base of the tomato plant. "Try not to get the lower leaves wet or let the water splash up onto the lower leaves to help prevent diseases from spreading," Bigg says.

If you're using granular or pelletized fertilizer, be sure to sprinkle it around the base of the plant as directed. Organic soil amendments, such as compost, manure, and alfalfa meal, should be mixed into the soil before planting your tomatoes. To help guide your choice, consider which application method is easiest for you, and think about if you want to use an organic or non-organic product. "I use both," Hawks notes. "Organic fertilizers improve the soil year-round and inorganic pumps up the volume on the producing."

Make Your Own Tomato Fertilizer 

There are plenty of different recipes you can follow when making your own tomato fertilizer, but Hawks recommends using a combination of mixed wood ashes, chicken or horse manure, and compost, like shredded leaves and grass clippings. Add the mixture to a five-gallon bucket and put it around the base of the plant, she notes. You can also include bone meal—a mixture of finely and coarsely ground animal bones—in your homemade fertilizer. The phosphorus-rich ingredient will give your fertilizer a nutrient boost. 

How and When to Fertilize Tomatoes

The method by which you feed your tomatoes depends on the type of fertilizer you're working with. Foliage spray, for example, needs to be applied directly to the leaves, while granular fertilizer should be sprinkled over the soil. Make sure you follow the manufacturer's label for step-by-step instructions—not doing so is why many people make the mistake of fertilizing their plants too much or too little, according to Hawks.

In terms of frequency, Hawks says she fertilizes the containers and beds of her tomato plants every two weeks. "When I see the plant start producing big tomatoes, that's when I gear back a little from fertilizing," she explains. If you're growing this variety in containers, Biggs says it's important to stay vigilant with your fertilizing; these types don't have access to nutrients in the same capacity as those growing in the ground would. "If you miss a week, it's not the end of the word," she says, "but staying on top of fertilizing will help to keep your plants healthy and thriving."

Our Top Tomato Fertilizer Picks

Tomato fertilizers aren't one size fits all, and which is why Biggs says it's best to choose a product that you think will fit your needs and use it as instructed. As for tomato fertilizers we like? Tomato-Tone Organic Fertilizer ($10.67, amazon.com) is an all-natural and organic option that's enhanced with thousands of microbes. The blend is jam-packed with 15 different nutrients and is specially formulated to produce tomatoes free of end rot. Another great option is Miracle Grow Tomato Plant Food ($12.49, amazon.com). The dissolvable formula starts working instantly when mixed with water and poured at the base of the plant. You can also consider an organic offering from Dr. Earth ($12.48, amazon.com). Beyond tomatoes, this fertilizer can be used for other vegetables, as well. The non-GMO feed contains 100 percent organic and natural ingredients, as well as probiotics, and seven champion strains of soil microbes. 

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