Why Are My Tomatoes So Small | 7 Common Causes And Solutions

Tomatoes are one of the most popular plants to grow at home. A true crowd pleaser, they are the main ingredient in so many dishes and sauces, and with some careful nurturing you should be rewarded with a fabulous glut of tomatoes by the late summer. 

But what happens if this year you get to that point only to find yourself asking the question ‘why are my tomatoes so small?’

There are 6 common reasons for tomatoes not reaching their full-size potential and they all relate back to the plant being stressed. Identifying the cause of the stress followed by a little TLC should allow you to resolve most cases. 

7 Common Causes Of Small Tomatoes

If a tomato is stressed it will stop sending its energy into fruit production and will choose to focus its energy on maintaining the roots. So even if your tomato plant is starting to wilt and is only producing tiny tomatoes chances are the root network will still be going strong! 

This does make many varieties of tomato quite hardy and therefore it is possible to turn some issues around if the roots have survived.

Small Tomatoes

Let’s explore the 6 main reasons a tomato plant may get stressed:

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1. Underwatering

Lack of water from drought or improper care is the number one reason tomatoes won’t grow. The soil should be kept consistently damp or the plants may show signs of stress such as wilting, leaf drop or just producing tomatoes that are too small. 

Always try to water early in the day and if a heat wave hits ensure you water twice daily. If your plant has not been left in a drought situation for too long, it is possible to revive it by getting back on top of your watering schedule and perhaps offering a feed too.

2. Lack of Sunlight

A lack of sunlight can impact the process of photosynthesis in plants, which leads to less available energy for growing fruit. Tomatoes ideally need 6 to 8 hours of sunlight per day

The best way to avoid this problem is to plant your tomatoes in a spot where there is plenty of sunlight throughout the growing season. Remember that a spot that looks sunny in early spring may be totally shaded by tree leaves later in the season. 

If your tomatoes are in pots or grow bags perhaps consider moving them to a sunnier spot to revive them. You need to provide enough space between plants so maybe consider thinning your crop out if they are too crowded and you have various plants.

3. High Temperatures

Tomatoes can only survive if the temperature consistently falls between 65 to 85 degrees Fahrenheit. Any temperature rising above or falling below this range can cause your plant to suffer water loss. This eventually leads to reduced photosynthesis, causing smaller-sized tomatoes or potentially no fruit at all.

If you live in an area that has a mixed summer climate and temperatures are known to drop, then a greenhouse is the best option to maintain some consistency. Likewise, if temperatures can get excessive it is important to go for a variety that is more tolerant to extreme warmth or perhaps plant them in pots so you can move them around. 

If you are faced with an unprecedented hot spell and you are not able to move your plants you may want to consider some temporary shade. You will also need to ensure they get sufficient water during the heat wave.

4. Damaged Roots Caused By Transplanting

The damage to roots during transplanting or inserting supports may affect fruit development.

Tomato plants have a very delicate root system and much of their effort goes into maintaining this – a good root system really will lead to a good crop of tomatoes and damaged roots will lead to stunted growth. 

Try and transplant your tomatoes while they are still seedlings.  Perhaps use a grow bag or pot to grow them in so you can minimize the amount of transplanting you need to do. Pop any canes or other supports in next to your plants whilst they are still small and then fasten the growing plant to it rather than inserting it at a later stage.

5. Over-fertilizing

Nitrogen is one of the vital nutrients required for the growth of tomato plants. However, excessive nitrogen application will lead to lush vegetive growth but smaller, tasteless tomatoes. So, it is always best to get a specific tomato feed.  These are readily available in most stores.

The effects of over fertilizing
The effects of over-fertilizing
Credit: Oregan State University CC by SA 2.0

6. Poor Pollination

Poor pollination can occur for a couple of reasons. One reason is extreme humidity levels.

Tomato plants are self-pollinating so to get fruit, the male part of the flower must release pollen onto the female part of the flower.

When humidity is too high, and the air is sticky the male part may have trouble releasing the pollen.  However, it is a fine balance, as when humidity is too low, the pollen will have trouble sticking to the female part of the flower as the air will not be sticky enough.

Another possible reason for poor pollination can be a lack of activity by pollinators. Extreme temperatures can impact their habitats, and food and make their survival hard thereby preventing them from doing their work. 

7. Incorrect Soil pH

Soil pH is a critical factor in growing any plant or vegetable, in that it has a direct effect on the plant’s ability to utilize the available nutrients within the soil. Tomato plants prefer a soil pH in the region of 5.8-7.0. This is the ideal range where the plant will be able to absorb all of the nutrients and minerals types around its roots. Leading to healthy and tasty crops.

Plants that yield small tomatoes or low crops are often disadvantaged by poor soil pH. No matter how much fertilizer you apply, the plant simply will not be able to make use of the resources. Furthermore, this overfertilization often leads to other problems including leaf scorch. Simply test the soil with a pH test kit prior to planting, and amend the soil using lime or sulfur.

You may also like to read Reasons for White Spots on Tomatoes

Other Reasons Your Tomato Plant Has Small Fruit

There are over 10,000 different varieties of tomato in the world ranging from the Giant Domingo Tomato to the tiny Micro Tomato, so it is perfectly possible you may have picked up a mislabelled product as the seeds and plugs all look so similar. It is also always wise to label your plants very clearly if you are growing multiple varieties as they will all produce different-sized fruit.

FAQ Why Are My Tomatoes So Small