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How to Fertilize Tomato Plants

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If you’re a tomato gardener, then you know that proper fertilization is key to getting the most out of your plants. But when and how should you fertilize tomatoes?

I will answer all of your questions! We’ll discuss what type of fertilizer to use, how much to apply, and when the best time to fertilize tomatoes is. So read on for all the details!

tomatoes growing on the vine

Why Tomatoes Need to be Fertilized

A favorite of the summer vegetable garden, tomatoes are a highly anticipated harvest each year. Tomatoes are also heavy feeders, which means they require a lot of nutrients to produce bountiful harvests.

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While most soil contains some level of nutrients, it’s often not enough to meet the needs of tomato plants. This is especially true if you’re growing tomatoes in containers. And while there are certainly things you can do to build up your garden soil which is incredibly important, feeding tomato plants is essential.

Tips for Planting Tomatoes

Before fertilizing, plant your tomatoes for a better chance at success. When it comes to planting tomatoes, there are a few things you should keep in mind. First, be sure to plant your tomatoes in an area that gets plenty of sunlight, 6+ hours.

marigolds and a tomato growing in a container
tomato and marigold growing in container

Tomatoes need at least six hours of direct sunlight each day in order to produce well. If you live in an area with long summers, then you can get away with planting tomatoes in an area that gets a little less sunlight.

Second, be sure to space your tomato plants accordingly. Depending on the variety of tomato you’re growing, they should be spaced anywhere from 24-36 inches apart.

And lastly, make sure you plant your tomatoes deep! This means burying them up to their first set of leaves. Doing this will encourage the plant to produce more roots, which means a stronger plant that’s better able to take up nutrients.

For more information on planting tomatoes, check out my other article Tips for Planting Tomatoes.

Now let’s move on to fertilizing!

The Best Type of Fertilizer for Tomatoes

Before applying fertilizer to any of your garden, I highly recommend having a soil test done. This will let you know exactly what type of fertilizer you’ll need to purchase (if any at all) so that you aren’t adding excess phosphorus or potassium to soil that may already be saturated. See my full post on How to Build Your Soil for all of the details.

I prefer using organic or natural fertilizers, so you’ll see most of my recommendations reflect this. Having your soil tested, and building up your soil with homemade compost is really one of the best ways to feed tomatoes. But if you’d like to fertilize, here are my recommendations.

When it comes to tomato fertilizer, you initially want to use something that’s high in nitrogen. Nitrogen is key for foliage growth, so it’s important to give your plants a good boost early on.

You can either use a balanced fertilizer with an N-P-K ratio of 10-10-10 if your soil can use more phosphorus and potassium, or one that’s high in nitrogen like blood meal which has a 12-0-0, fish emulsion 4-1-1, or Espoma’s Garden Tone 3-4-4. Just be sure to follow the package directions carefully!

As tomato plants begin to flower, you’ll want to shift to using a fertilizer that’s higher in phosphorus and/or potassium, such as

These nutrients are key for fruiting and flowering, so they’ll help your plants produce more tomatoes!

When and How Much to Fertilize Tomatoes

Now that we’ve discussed the best type of fertilizer for tomatoes, it’s time to talk about when and how much to apply.

If choosing to fertilize, then wait until the plant has its first true set of leaves, not the initial seedling leaves, but real tomato leaves. The seed coat of the tomato seed will give the seedling all it needs to grow and thrive, so hold off on fertilizing until the real leaves begin to establish.

Fertilizer being applied after the first real leaves appear

As far as when to fertilize for the season, a classic master gardener response to this and many gardening questions is, “it depends.” And this is true of questions regarding how much and how often to fertilize tomatoes. Follow package instructions for your specific fertilizer, and feel free to experiment.

Your observations will guide your fertilization schedule. If your tomatoes are producing well, then consider holding back on fertilizing anymore that season, or if you have lots of green foliage growth, then skip the high nitrogen fertilizer.

Did your soil report show that your soil was rich in minerals and phosphorus and potassium? Then keep an eye on your plants and only feed your tomatoes if you notice a failure to thrive. There’s a lot of trial and error in gardening, so you’ll want to find what works for you.

Applying fertilizer to tomato plants

No matter when you’re applying fertilizer, you’ll want to be sure not to get any on the leaves of the tomato plant as this can cause them to burn. Instead, focus on the root zone and either work it into the soil around the base of the plant or water it in well.

Also keep in mind that some more natural fertilizers may attract dogs and other pets. I know our pups love any fertilizer that has composted chicken manure in it, so just be aware.

I hope this article has helped clear up any confusion you had about when and how to fertilize tomatoes! If you have any questions, or if I missed anything, please feel free to leave a comment below. And be sure to check out my other articles on growing tomatoes:

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