Why tomatoes crack as they ripen and how to prevent it

One of the more frustrating things about growing tomatoes is watching a tomato ripen on the vine, slowly growing and changing from green, to pink, to red…. and then looking one morning and seeing that that tomato you’ve been waiting for has cracked.

What is cracking?

Cracking is the splitting of the epidermis around the calyx or stem scar. There are two types of fruit cracking in tomatoes.

1.  Concentric cracking, which is a splitting of the epidermis in circular patterns around the stem scar.
2. Radial cracking which is a splitting of the epidermis from the stem scar towards the blossom end.

When Does racking occur?

Cracking occurs as the tomato nears maturity. More susceptible varieties crack in the mature green stage and more tolerant varieties at later stages. The earlier the cracking then the deeper and longer the crack becomes. The problem is usually more severe on the lower trusses. Circular cracking often occurs on ripe tomatoes that are on the vine too long.

What Causes Tomatoes to Split?

Side splitting and cracking up are terms you want to hear in reference to a joke you just made, not about your tomatoes. Heavy rain, especially when preceded by dry weather, is the leading cause of fruit cracking and splitting in tomatoes. This type of damage is most likely to occur as tomatoes begin to ripen and you are anxiously anticipating harvest, though green fruit can be effected as well.

Cracking and splitting occur when rapid changes in soil moisture levels cause fruits to expand quicker than the tomato skin can grow. There are two different patterns this damage may take. Vertical splits along the sides of fruits are known as radial cracking and are the most serious. This pattern of splitting commonly occurs during hot, humid weather. Cracking that occurs in a circular pattern at the top of tomato fruits, ringing the stem end, is known as concentric cracking. When cracking of either type occurs in green tomatoes, fruits are likely to rot before they fully ripen if left on the vine.

Tomatoes with radial cracks will rot quickly if left on the vine.

With both radial and concentric cracking, your best option is to harvest fruits immediately, before they begin to rot. These fruits are edible and can be allowed to finish ripening indoors, though any fruit that develops a sour smell or begins to ooze should go straight to the compost pile. Fruits that ripen off the vine, as well as those that ripen on the vine during cloudy, rainy weather will be less flavorful than those that mature fully on the plant during sunny weather.

How to Prevent Tomatoes from Splitting

The most important thing you can do to minimize fruit cracking in tomatoes is to maintain even soil moisture levels by watering during drought. Most vegetables require around one inch of water per week to remain productive. Soaker hose and drip irrigation systems are the best way to provide this water to vegetable and ornamental plants because these systems apply water directly to the soil. This reduces water loss through evaporation and keeps plant leaves dry, which helps limit the spread of leaf diseases. Mulching your vegetable garden will also help keep the soil evenly moist and minimize moisture related problems.

Cracking tomatoes are just one of those things that every vegetable garden seems to deal with at one time or another. The good news is that cracked tomatoes are still edible, so feel free to harvest and eat them. They won’t store long, so be sure to eat or cook with them right away.

Now that you know how to protect your tomatoes from cracking, here’s hoping you have a beautiful, bountiful harvest.