Ultimate Guide: The 5 Secrets to Increasing Fruit Size in Tomatoes

Growing the biggest tomatoes you possibly can is traditionally a rite of passage, something that fledgling gardeners learn over the course of years of gardening.

Year after year, they improve the soil.

Carefully tend their plants.

They miss a major pest or disease issue, or fail to fertilize correctly.

They have smaller harvests some years.

They have total crop failures other years.

Eventually, these gardeners gain the experience and touch that they need to grow the biggest, juiciest, finest tomatoes in town; and they become the new standard, rather than an occasional victory.

If you’ve been trying your hand in the tomato garden and are still struggling with growing the biggest tomatoes you’ve ever seen, then give this post a go; and don’t forget to share it with other struggling gardeners!

How Do You Increase Fruit Size In Tomatoes?

If you want to increase your overall fruit size among your tomato plants, you have to provide them with plenty of space both above and below ground, plenty of water (consistently), lots of sunshine, and plenty of the correct nutrients.

You will also need to keep your plants pruned and clean in order to maximize fruit size, which may require quite a bit of time as the summer continues. It may all sound fairly standard, but you might be surprised at what you missed in previous seasons!

1: Amending Soil and Transplanting Tomato Plants Correctly

If you’ve not yet transplanted your tomato plants into the garden, you must start here.

Tomatoes enjoy a slightly acidic soil, roughly 6.0 to 6.8 pH. They also enjoy a loamy soil over clay, so you need a bed that will allow their roots to grow freely. For those of us who grow tomatoes in clay, it’s just a bit more difficult to get them to grow the biggest tomatoes- definitely not impossible, though!

For the best tomatoes, you’re going to require a soil test. You need to know what your soil is deficient in and what it has plenty of; a balance of nutrients is vital for prime tomato production. If nitrogen is plentiful and you add too much excess, your plants will grow to be bushy and beautiful, but at the expense of a decent fruit harvest; if calcium is low, it may cause blossom end rot. Other nutrients in excess can inhibit uptake of vital nutrients, causing other major issues with deficiencies.

Thus, you’re going to need to know what’s in your soil before you add to your soil.


Once the soil is amended, prepare a large planting hole with loosened soil, and bury the tomato plant 2/3 of the way. This will leave little above the soil line, but that’s what you want!

The length of the main stem will root once planted, giving your plant a strong root system that’ll prevent the plant from toppling over. The loose soil will allow the roots to grow and expand freely and rapidly. This allows for rapid uptake of water, nutrients, and minerals from the soil, which is important as the plant becomes large. A struggling root system results in a struggling plant.

Providing Support

As your plants grow larger, they will need support. I don’t recommend tomato cages for MANY reasons, so I recommend stronger supports. As the plants grow and widen, these supports will be vital for keeping your fruits off of the ground and preventing fungal diseases. They’re also important for air circulation.

2: Providing Plenty of Water for Improved Tomato Size

Tomatoes are very juicy fruits; they require lots of water as they grow and ripen. When a tomato plant is quite large and growing dozens of fruits at a single time, you’d be surprised at how much water it requires.

During the heat of summer, the rate of transpiration will be high. If your tomato plant is losing more water than it can absorb from the soil, the plant will go into stress. Fruits will be smaller, flowering may stall, and overall growth may slow or stop.

When water stress is prolonged, blossom end rot is a common issue. If you experience BER in your tomatoes, begin watering them on a more consistent schedule. Thereafter, blossom end rot should not appear on new fruits; if it does, you’re dealing with a calcium deficiency.

Many believe Epsom Salt prevents blossom end rot, but it doesn’t. However, Epsom Salt has an incredible benefit for tomato plants that isn’t widely discussed, so it’s still beneficial! Just know that, even with Epsom Salt, you may still experience BER.

Be sure that the soil around the plant is moist, not dry. You don’t want water logged soil- just soil that is moist. If you’re in the middle of summer, you may have to water your plants every evening; container grown tomatoes may require water twice daily. You’d be surprised that simply watering plants consistently will help you increase fruit size in tomatoes!

3: Full Sunlight Is Vital for Tomato Growth

If you plant your tomato seedlings in an area that is partially shaded, they will not grow to their full potential; neither with the fruits that those plants yield.

With full sunlight, tomato plants can yield all the energy that they require from the light, preventing them from depriving their fruits of energy and nutrition.

Be sure that plants are spaced and thinned properly too, or they may heavily compete with one another for light as the season progresses. Tomato plants can and will shade each other out, as they can reach over 12′ in length.

4: Keep Your Tomato Plants Pruned Often

Indeterminate plants will produce hundreds of suckers throughout the growing season. Keep your plants sucker-free for as long as you can through the summer, as eventually, it will become nearly impossible to remove all of the suckers.

When a tomato plant develops several suckers, the root system will have to work harder to provide enough nutrients to each fruiting branch. The fewer fruiting stems the plant has, the larger the fruit will be. Removing suckers maximizes yields in small spaces, and allows the existing and future fruits to grow larger and ripen faster.

Prune the lower branches that are below the lowest green fruits, too. Any branches that are below existing fruit can be removed, as long as they are not leading to a fruiting cluster (main stem, or sucker.) These leaves can be removed safely, and are likely shaded far too much to be considered productive for the plant. Some may already be yellowed and dying, so removal is beneficial. By removing them, you preserve the plants resources (energy and water), you promote airflow around the plant, and you reduce the risk of fungal infections due to water splashing during rain showers.

5: Feed Tomatoes the Correct Fertilizer as Needed

If you’re starting out, a lot of companies have made fertilizing easy; there are tomato-specific fertilizers available in nearly any home improvement, department, or gardening store. Each container will have detailed instructions on use, telling you how to apply it, how to mix it, and how often to use it for optimal results.

Most have the same NPK values or are very close; they’re designed to promote tomato plant growth and high fruit yield. They also help you to increase fruit size in tomatoes as they supply most of the nutrients that the plant needs directly to the roots- eliminating the need for roots to go in search of those nutrients deeper in the soil.

However, you may shell out unnecessary cash for these fertilizers, and you may also have a hard time finding organic or natural tomato fertilizers.

If you don’t want to spend extra money on “specialty” fertilizer, opt for a 5-10-5, which provides extra phosphorus for the tomato plant. Be sure to add a little compost or compost tea throughout the season, as they are an excellent, natural way to boost your soil’s fertility and health. Worm castings are excellent, too!