Fertilizing Tomatoes: How And When To Fertilize Your Tomato Plants

  • Date: June 22, 2022
  • Time to read: 13 min.

Growing tomatoes is a very rewarding experience. After a long season of caring for your crops, you get to enjoy some juicy and sweet fruits! What could be better than that?

Fertilizing Tomatoes: How And When To Fertilize Your Tomato Plants
Fertilizing Tomatoes: How And When To Fertilize Your Tomato Plants

However, growing tomatoes can be quite an intimidating process, especially when it comes to fertilization.

There is an overwhelming amount of information out there regarding when and how to fertilize, and what you should be fertilizing with. 

That’s why we are here to help. To learn how to fertilize your tomatoes during each stage of their growth cycle, take a look at the information below. 

We also include lots of handy information on fertilization, in general, to ensure that you are equipped with all of the necessary knowledge.

And, there’s a handy FAQ section at the end so that all of your questions are answered! 

When To Fertilize Your Tomato Plants

Fertilizing Tomatoes How And When To Fertilize Your Tomato Plants
Fertilizing Tomatoes: How And When To Fertilize Your Tomato Plants

Now that we’ve covered the basics, let’s get into the good stuff! When it comes to tomato plants, when to fertilize, and what to fertilize with, depends completely on where the plant is in its life cycle.

Below, we’ve listed the prime fertilizing times in a tomato plant’s life.

We’ve also recommended certain formulas depending on what your tomato plant needs during the specific growth stage. Check it out. 

Fertilizing Seedlings

If you start your tomato plants off by growing the seeds indoors, we recommend fertilizing them lightly right from the very beginning.

Doing this will give your seedlines a really great chance to grow into strong and robust plants. 

If you decide to do this, we recommend opting for a slow-release organic fertilizer. Combine the fertilizer with your seed-starting before you plant your seeds. Make sure that you water them well once planted. 

Fertilizing During Planting 

When you are transferring your seedlings into the soil in your garden, they could benefit from a little boost.

As such, we recommend packing the planting holes full of quality nutrients so that your seedlings are able to grow well. 

You could use good-quality compost, ¼ of worm castings, or another organic slow-release fertilizer.  These will ensure that your seedlings are receiving nutrients over a long period of time.

Fertilizing During Flowering Period 

When your tomato plants begin to flower, they need plenty of nutrients. Specifically, they require lots of potassium.

This essential nutrient works to ensure strong, robust, and healthy growth, and a considerable amount of flowering. 

At this stage, whatever fertilizer you are using should have a potassium content of at least two times the nitrogen content. We recommend opting for a fertilizer with an N-P-K value of either 8-32-16 or 6-24-24. 

Fertilizing During Fruit Growth 

Now you have to keep a close eye on how your tomato plants are doing. There is no strict rule regarding fertilizing your plants at this stage of their growth, so you need to keep an eye out for any signs that they may be lacking in certain nutrients. 

The nitrogen that you provided by composting is likely to still be supplying your plants with enough nitrogen, so you generally don’t need to worry about this nutrient.

Instead, you should be vigilant for signs of a phosphorus or potassium deficiency. 

For example, if the fruits aren’t developing as they should be, it is likely that you will need to add some fertilizer to the soil.

We recommend that you opt for one with an N-P-K value of something like 8-32-16.

Fertilizing At The End Of The Growing Season 

You likely won’t need to fertilize very much in between fruit development and harvesting stages.

You can lightly fertilize your plants every few weeks to ensure a good yield, but it is especially important that you don’t over fertilize during this time. 

Phosphorus remains to play a vital role during this stage, so we recommend opting for a phosphorus heavy fertilizer if you do choose to use one.

Indeterminate tomato plants may need fertilizing more frequently during this stage because they fruit over a longer period. 

How To Fertilize Tomato Plants

How To Fertilize Tomato Plants
Fertilizing Tomatoes: How And When To Fertilize Your Tomato Plants

Now that you know when to fertilize your tomato plants, let’s discuss the best fertilizing methods to ensure that your garden receives all of the nutrients it needs to thrive. Check out our general fertilizing method below. 

Each Plant Is Different 

But first – we need to mention that all plants are different.

The right way to fertilize your tomato plant will depend significantly on the variety of the plant, the type of soil, where you are planting your plants, and the specific fertilizer that you are using. 

For example, plants that are planted in sandy soil require more fertilizing than those planted in clay-like soils because sandy soils struggle to hold onto nutrients.

Similarly, if you plant your tomatoes in containers, they will use up nutrients more quickly than those in the ground. 

As such, it is very important that you learn as much as you can about your soil, your plants, and the fertilizer that you are using.

We recommend that you follow the instructions on your chosen fertilizer carefully. 

Fertilizing Rules

There is a right way to fertilize your tomato plants. If you fertilize your plants improperly you could cause far more damage than good. To ensure that you are getting the best results, take a look at our fertilizing rules below. 

First Add Organic Matter

Before you plant your tomatoes, we always recommend adding a few inches of compost or manure to the soil.

If you don’t plan on using inorganic fertilizers as your tomatoes grow, this step is especially important. The organic matter will provide the plants with vital nutrients.

Be Careful Where You Fertilize 

It is never safe to apply your fertilizer all over the plant. In fact, fertilizing too close to the plant could cause it to burn.

When fertilizing, make sure that you do not get any fertilizer on the leaves or stem, because this can cause a huge amount of damage. 

Combine The Fertilizer With The Soil 

It is very important that you always mix your fertilizer with the soil. We recommend digging a small trench about 6 inches away from the plant.

Then, sprinkle your fertilizer into the trench, and cover it with soil when you’re done. 

Water Appropriately 

Finally, it is very important that you are watering your tomato plants correctly. If you aren’t, it is unlikely that they will receive the benefits of fertilizing.

This is because the water enables them to absorb the nutrients. 

Tomato plants can be quite thirsty. They require deep and thorough watering at the base of the plant. We recommend doing this at cooler times in the day, such as the morning or evening. 

The soil should never be allowed to dry out completely. As such, we recommend watering your tomato plants every few days.

However, if you live in a particularly hot climate, you may need to water them more frequently. 

We also recommend watering your plants before they have been fertilized, rather than after.

However, if your specific fertilizer instructs you to do it the other way around, then you should follow those instructions. 

Best Fertilizers For Tomatoes 

Now that you are equipped with all of the tools to ensure that your tomato crops truly thrive this growing season, there is just one more thing you need – the fertilizer!

Check out our favorite fertilizers for tomato plants below. 

Dr. Earth Home Grown Fertilizer

[amazon fields=”B079TC6H83″ value=”thumb” image_size=”large” image_align=”center” ]

If you are concerned about the effects of GMOs on your crops, the Dr. Earth Home Grown FErtilizer is an excellent option. In fact, it is the only non-GMO verified fertilizer in the whole of the USA. 

This organic fertilizer has an N-P-K ratio of 4-6-3. As such, this is a great fertilizer to use during the flowering stage of your tomatoes’ life cycle.

It is enriched with multi-minerals, proteins, carbs, humic acids, and trace elements that promote the healthiest soil possible. 

Jobe’s Tomato Fertilizer Spikes

[amazon fields=”B001REDIZ2″ value=”thumb” image_size=”large” image_align=”center” ]

Jobe’s has a great reputation for producing high-quality fertilizers, and this one is no exception. It is very affordable and particularly effective.

And, these fertilizer spikes make fertilizing your tomato plants incredibly easy and stress-free!

It has an N-P-K value of 6-18-6. As such, this is a great fertilizer to ensure that the flowering and fruiting processes go off without a hitch. It will also ensure that the root system grows robustly.

The spikes feed plants for 8 weeks, so this is a very hassle-free fertilizer!

Greenway Biotech Tomato Fertilizer

[amazon fields=”B012E72PTK” value=”thumb” image_size=”large” image_align=”center” ]

This fertilizer is quite a bit more expensive than the others on this list. However, it is definitely worth the extra money. Due to the fact that it is water-soluble, a little goes a very long way! And, it has an impressive formula that is bursting with useful minerals and nutrients. 

It has an N-P-K ratio of 4-18-38 and boasts ingredients including potassium, boron, copper, iron EDTA, manganese EDTA, zinc EDTA, and molybdenum. It is also free of heavy metals and harmful minerals, making it a truly excellent choice. 

Espoma Tomato-Tone Organic Fertilizer 

[amazon fields=”B0011UEKKE” value=”thumb” image_size=”large” image_align=”center” ]

This affordable fertilizer has a great reputation when it comes to producing delicious and large yields.

It consists of a rich blend of the finest natural and organic ingredients. It has also been enhanced with an exclusive 3-4-6- formula that works to prevent disease. 

This is a great option for anyone who wants to keep their garden as organic as possible.

It is a registered Organic Input Material, which means that it meets all of the stringent requirements for organic production. 

JR Peter’s 51324 Jack’s Classic Tomato Feed 

[amazon fields=”B01C9WRH0M” value=”thumb” image_size=”large” image_align=”center” ]

Finally, we had to mention the great JR Peter’s 51324 Jack’s Classic Tomato Feed. It is a water-soluble plant food that is packed with micronutrients that your tomato plants (and others) will love! 

The higher potassium content ensures that you receive a good quality and large yield at the end of the growing season.

In fact, after using this fertilizer, you can expect strong vines, bright foliage, and a lot of fruit. 

What Nutrients Do Tomato Plants Need?

It’s important to understand exactly what nutrients tomato plants need.

It may vary slightly depending on the type of tomato plant you have, but generally speaking, tomatoes tend to be heavy feeders.

If your tomato plants aren’t fed enough or don’t have access to one type of necessary nutrient, it is likely that the overall health of your plant will suffer.

In turn, your harvest is likely to be rather disappointing. 

To avoid this unpleasant scenario, take a look below at the vital nutrients that tomato plants need to grow.

Each one plays a vital role in the development of tomato plants, from the growth of their leaves to the plumpness of their fruits. 

Nitrogen (N)

Nitrogen is one of three primary nutrients that most plants require. It is vital for ensuring that the leaves and stems of tomato plants grow appropriately and robustly.

As such, nitrogen-heavy fertilizers tend to be used when tomato plants are young. 

However, there is a downside to this nutrient.

If you overwhelm your plants with nitrogen, or you give them nitrogen when they should be expending energy on producing flowers and fruits, it’s likely that you will be left with a partially bushy plant with a very small yield. 

Phosphorus (P)

Phosphorus is the second of the three primary nutrients. Most plants need phosphorus to help their roots grow and develop resiliently.

Additionally, phosphorus is also responsible for the growth of good fruits. 

As such, phosphorus differs from nitrogen in one vital way: it is appropriate to feed a tomato plant phosphorus during both the early and late stages of its life cycle.

This will ensure a good root system and a high yield.

Potassium (K)

Potassium is the third of the primary nutrients, and it is essential during the flowering stage of a tomato plant’s life cycle. 

Whilst potassium does aid in the formation of flowers, it is also a vital part of the photosynthesis process and aids in disease prevention.  


In addition to the three primary nutrients, there are other elements that tomatoes require to grow well.

Specifically, calcium is required to ensure that the roots of the tomato plant grow deeply and robustly. It also aids leaf growth and the production of firm fruits. 


Magnesium is another vital ingredient in a tomato plant’s growth cycle.

In fact, without the right amount of magnesium, your plant won’t be able to remain green. It may turn yellow or wilt. Magnesium also helps to boost the quality of the fruit produced.

Zinc & Boron

Finally, you will notice that many fertilizers and foods mention that they include zinc and boron.

These elements aren’t quite as vital as the others listed here, but they do help to ensure that the flowering and ripening processes occur smoothly. 

Understanding Fertilizers

Fertilizers can be confusing – whether you’re a total beginner or a green-fingered gardening enthusiast.

But, it is essential to understand them if you are to make the most out of your garden. 

Before we dive into the details regarding how and when to fertilize your tomato plant, check out the information on fertilizers below. We cover everything you need to know to have a thriving garden!

N-P-K Ratio

The most important thing to understand when it comes to fertilizers is the N-P-K ratio.

This ratio describes the amount of nitrogen (N), phosphorus (P), and potassium (K) that is a certain fertilizer’s formula. 

For instance, if a fertilizer states that it has an N-P-K formula of 10-10-10, this means that it is formed of 10% nitrogen, 10% phosphorus, and 10% potassium. In this formula, there is an equal amount of each primary nutrient. 

However, some formulas are targeted toward certain problems. For example, a formula may have a higher nitrogen content in order to encourage foliage growth.

Or, a formula may be higher in phosphorus to aid with root establishment. 

Types Of Fertilizer

Fertilizers can be categorized into two broad groups: inorganic and organic. Generally speaking, the use of either comes down to personal preference.

To learn more about the difference between organic and inorganic fertilizers, take a look at the information below. 


Inorganic fertilizers are man-made. They can consist of naturally occurring minerals and/or synthetic plant nutrients.

Inorganic formulas usually work faster and tend to be specifically tailored to help prevent or solve a particular problem. 


Organic fertilizers are those that have been made using plant or animal sources. They contain plant nutrients in their organic form.

These are usually slower to act than their inorganic counterparts, however, they are preferred by many because they are more natural. 

Frequently Asked Questions 

If you still have some fertilizer-related questions, don’t worry! We know just how confusing this topic can be.

Take a look at our answers to some of the most frequently asked questions below. You’ll be an expert on tomatoes and fertilizers in no time!

How Can I Tell If I’ve Fertilized My Tomatoes Too Much? 

Unfortunately, it can be quite easy to over fertilize your tomato plants, and this can lead to some dangerous consequences.

In fact, many people may stay away from fertilizer because overfertilization can cause much more damage than a lack of nutrients. 

However, overfertilization can be fixed if you spot it early enough. Below, we’ve listed the most common signs of overfertilization. We’ve also listed some handy tips to help you fix the situation. Check it out. 

Signs Of Overfertilization

  1. Yellow Leaves
  2. Bushy Leaves
  3. Delayed Flowering Stage
  4. Sediment Build-Up 
  5. Sudden Leaf Loss
  6. Wilting Of Lower Leaves 

How To Fix Overfertilization 

Fortunately, you can generally fix the problem of overfertilization, as long as too much damage hasn’t been done already! Follow the steps below to get your tomatoes back on track. 

Step One: Mulch 

First, you should add an organic mulch around your tomato plants. The mulch has to be organic so that it decays over time.

For the best results, you can also mix sawdust into the ground. This will speed the process up. 

Step Two: Remove Sediment 

If you have noticed white sediment on the top of your soil, you should scrape it off. This is a sign that you’ve added too much fertilizer. Removing it will help to restore your soil back to its original state. 

Step Three: Soak 

Finally, if you are growing your plants in containers, soaking the soil can help to solve the problem.

If you grow your plants in the ground, we recommend soaking the soil multiple times. This will flush out the excess fertilizer.

Can You Water Tomatoes During The Day? 

Yes. However, you shouldn’t water them when it’s too hot, because much of the water will be lost. Instead, we recommend watering your tomato plants in the early morning, when the warmth from the sun is still minimal. 

Some people chose to water at night. However, this can cause problems. For instance, it can increase your plants’ vulnerability to fungus, blossom end rot, and root loss.

As such, keep an eye out for these problems if you plan on watering your plants in the evening. 

Should You Cut The Bottom Leaves Off Tomato Plants?

Generally speaking, yes. Regular pruning, particularly at the bottom of the plant, will be beneficial for your tomato plants. In fact, this could help to increase the size of your yield at the end of the growing season.

Rather than letting leaves grow around the base of your tomato plant, we recommend that you cut them using a sterilized pair of gardening scissors when they are small.

This will ensure that the plant’s resources are directed toward flowering. 

Can You Use Epsom Salt On Tomato Plants? 

Yes! Using a spray made from Epsom salt and water towards the end of the growing season may work to increase your yield!

It also helps to keep your plants looking green and healthy. You can also use it earlier in the season to help with important processes such as root development and photosynthesis. 


The process of fertilizing your tomato plants can be quite intimidating, especially if you’re new to the wonderful world of gardening.

We hope that this article has given you the tools you need to have a thriving crop this growing season!

Why Are The Leaves On My Tomato Plants Turning Brown?s

Previous Post

Why Are The Leaves On My Tomato Plants Turning Brown?

Next Post

Hydroponic Tomatoes: How To Easily Grow Tomatoes Hydroponically

Hydroponic Tomatoes: How to Easily Grow Tomatoes Hydroponically