7 Reasons Your Tomatoes Are Splitting or Cracking on The Vine

It’s incredibly frustrating to put months of hard work into your tomato plants, only to discover cracked or split fruit when it’s time to harvest. While these tomatoes are usually still edible, they may look unappetizing or unattractive for your summer recipes.

Preventing tomato splitting is all about carefully managing your tomato crop with optimal irrigation, mineral amendments, site preparation, and harvest timing.

So, if you’ve seen splitting tomatoes this season, understand that you are not alone. This is a common problem for tomato gardeners, but can be prevented if you understand why it’s happening. Here’s everything you need to know about growing crack-free tomatoes that you can enjoy straight from the vine.

Why Do Tomatoes Split on The Vine?

The most common reason for tomatoes splitting on the vine is water fluctuation. If the soil regularly dries out and then gets flooded with a lot of water at once, tomato fruit size outpaces the growth of the skin and causes splitting.

This can happen when heavy rains come after a period of drought. Or, it can happen when you forget to water your tomatoes during the fruiting phase.

However, fixing your tomatoes’ watering regime doesn’t always solve fruit cracking problems. There are several other potential reasons for tomato splitting that we’ll cover below.

Types of Cracking

Tomatoes can split in two different ways: vertical (longitudinal) cracking and concentric cracking. Vertical splits typically extend from the top of the fruit to the bottom. Concentric cracks most often appear on the top stems of heirloom and beefsteak varieties.

Both forms of cracking can cause premature rotting, diseases, or access points for pests. Fortunately, concentric cracking isn’t usually as severe. It won’t typically harm the marketability of a tomato (for farmers) nor the flavor and culinary use (for gardeners).

It is generally considered safe to eat cracked tomatoes as long as they don’t appear to be rotting or infested with bugs. The main downside to cracking is that they don’t last as long in the kitchen and are less aesthetically pleasing.

7 Reasons For Cracking and Splitting

Solving your tomato cracking problems is all about getting down to the root cause. And… you guessed it! The root causes are most often in the root zone. The soil moisture, mineral levels, and texture can have major impacts on fruit quality. You may also be harvesting your tomatoes too late or choosing varieties that are notoriously prone to splitting.

Water Fluctuations

Uneven watering is the root cause of most all tomato cracking issues. As the plant tries to cope with differences in dry, drought periods and soggy, wet periods, as well as hot daytime temperatures and cool nighttime weather, fruit inevitably suffer.

Because tomato fruits are up to 95% water, they can easily crack when the plant is suddenly flushed with rain water or irrigation after a period of dryness. The skins of ripe fruit are especially prone to suddenly bursting and subjecting to unattractive cracking.

In order to fix the problem, you’ll want to maintain even and consistent soil moisture as possible. Don’t allow the root zone around tomatoes to dry out, nor get soggy.

You should regularly check the soil moisture with your finger or a moisture probe. You can also use irrigation timers, additional soil organic matter, or surface mulches to maintain adequate hydration

Overwatering Before Harvest

Similar to inconsistent watering, overwatering tomatoes is another common reason for splitting. If you don’t regularly check the soil moisture before irrigating, you may inadvertently flood your tomatoes with water that they don’t need. This can predispose them to more rotting and disease issues. It can also cause premature splitting in almost-ripe tomatoes.

After a big drench of rain or irrigation water, fruit membranes can swell and split through the skin. Overwatering can also cause less flavorful tomatoes and waterlogged soil that makes plants less productive.

In order to fix this issue, you’ll want to make sure you check the soil before watering to be sure it isn’t soggy. It is widely considered the best practice to reduce tomato irrigation just before harvesting.

If you harvest tomatoes every few days, avoid watering on the day of picking. It also helps to pick tomatoes in the morning or evening. This is when the ambient air is more humid and the sugars are more concentrated.

Calcium Deficiency

Calcium deficiencies are most commonly associated with blossom end rot. Blossom end rot causes black water-soaked or rotten lesions on the “butts” of tomatoes. Low calcium can also predispose tomatoes to cracking because it is so closely linked to water uptake and ripening.

Interestingly, this mineral is also closely linked to magnesium and potassium levels.

In order to fix this issue, a foliar spray of calcium solution can be applied 2-3 times per week for a “quick fix” to cracking and blossom end rot. However, a longer term solution involves amending the soil with slow-release organic calcium fertilizers such as eggshells or oyster shell. Amend these directly into the soil about 4-6” deep before planting tomatoes.

Poorly Drained Soil

Like most garden crops, tomatoes prefer well-drained loamy garden soil. When the soil is heavy, dense, and poorly drained, it can quickly become waterlogged and cause fruit splitting problems. This is because the tomato roots need to breathe just like we do.

The lack of aeration in the root zone leads to a suffocating effect that impedes water uptake and predisposes the plant to more disease issues. 

Once tomato plants are already rooted and growing, it will be difficult to improve the soil drainage. Your best bet is loosening around the base of the existing plant with a hoe. Then mulch with a quality compost.

In the future, be sure to thoroughly broadfork your garden soil. Then generously amend with rotted manure, peat moss, compost, or shredded leaf mulch. Don’t overwater your plants. Avoid tillage when possible (especially in clay soils), because this can cause further compaction and waterlogging.

Over-Ripening

Vine-ripened tomatoes are far more flavorful than their green-picked, artificially-ripened counterparts. However, if you leave tomatoes on the plant for too long, they can become more prone to cracking.

As tomatoes ripen, the inner fruit becomes more swollen as its sugars become more concentrated. In the event of heavy rain or prolonged irrigation, over-ripe fruit can spontaneously burst through the skin. It can create holes for pests or fungi to enter the fruit.

In order to fix this issue, picking fruits slightly under-ripe is the easiest way to combat tomato splitting. This is especially important before heavy rain. If you can harvest as many fruits as possible before a downpour, you will likely save your yields and enjoy more crack-free tomatoes.

When ripening tomatoes on your countertop, put them near a bunch of bananas to promote more ethylene production (the natural plant hormone that triggers ripening).

Varietal Selection

Certain varieties of tomatoes are more prone to cracking and splitting, while others are bred to be resistant. For example, heirloom varieties like ‘Beefsteak’ and ‘Cherokee Purple’ tend to have very large fruits that are prone to vertical cracking on the blossom end or concentric cracking on the tops.

The genetics, shape, and size of these tomatoes makes them notorious for splitting, especially in hot weather with lots of water in the soil. 

It’s always best to pick crack-resistant cultivars like ‘Jetstar’, ‘Roma’ and ‘Pruden’s Purple’  are bred to grow smooth, moderately sized tomatoes that are resilient to water fluctuations and splitting. Cherry tomatoes like ‘Black Cherry’, ‘Gold Nugget’, and ‘Sun Gold’ are other great cultivars that are less prone to cracking.

Exposed Fruit

Tomatoes are infamous for how much they love the warm summer sun. However, the fruits themselves prefer to be shaded by tomato leaves. If significant amounts of tomato foliage are pruned away or lost to other problems, the fruits can become more susceptible to a condition called sunscald.

This overexposure of tomatoes to harsh sun rays leads to discoloration and uneven ripening, which quickly cascades into cracking and rotting issues.  

To fix this issue you’ll want to maintain an adequate canopy cover to protect developing tomato fruits. Avoid over-pruning upper leaves to ensure that fruits are not left “naked” and exposed to the sunlight.

If you lose significant foliage to common tomato pests or diseases, consider harvesting the tomatoes early or using a temporary shade cloth to protect them.