Tomatoes: Fruit Splitting And Cracking / RHS Gardening

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Tomatoes: fruit splitting and cracking RHS Advice Guide Although easy to grow, tomato fruits can suffer from splitting and cracking in late summer. This is difficult to prevent, as it is caused by fluctuating temperatures and water supply - which are often out of the control of the gardener.

By The RHS Advice Team

• Quick facts
• What is the problem?
• Symptoms and causes
• Biology
• Control

Quick facts

Plants affected - Tomatoes.

1

Main causes - Variation in temperature and soil moisture can lead to split, cracked fruits.

2

Timing - Summer.

3

What is the problem?

This is an example of a physiological disorder – a problem caused by the growing conditions rather than by a pest or disease agent. Inappropriate levels of water, light, temperature and nutrients To grow well, plants need a wide range of nutrients in various amounts, depending on the individual plant and its stage of growth. The three key nutrients usually taken up from the soil are nitrogen, phosphorus and potassium. Plants also need carbon, oxygen and hydrogen to make carbohydrates — their main energy source. Carbon and oxygen come from the air as carbon dioxide, while hydrogen is drawn from water absorbed by the roots. Other important soil nutrients include magnesium, calcium and sulphur. Most garden soils contain enough of these nutrients to support healthy plant growth. can all cause a variety of physiological disorders in tomatoes. The fruits are especially vulnerable as they are at the growing tips and have to compete with the new shoots for water and nutrients.

Symptoms and causes

• Split, cracked or heavily russeted fruit: This is usually caused by variable water supply and/or fluctuating temperatures.
• Corky scars and irregular concavities in the fruit, known as ‘catfacing’: This is usually caused by variable temperatures.

Biology

• The ‘catfacing’ symptom is due to temperatures fluctuating too widely early in the season as the fruit is setting. It tends to occur early in summer, declining as the nights become warmer in late summer.
• Russeting (a rough skin surface) and superficial marks are caused by variable temperatures, whereas cracking and splitting are due to fluctuations in soil moisture.
• Water supply can be especially variable in growing bags and pots, and this requires regular monitoring both in the greenhouse and outside. Outdoors, variations in rainfall may cause damage. Although watering in dry spells will help, in periods of heavy rain there is no remedy for the damaging effects of flooding, which often leads to fruit splitting and cracking. Prompt harvesting of fruits may reduce losses.
• ‘Stop and start’ growing caused by insufficient warmth and fluctuating temperatures or moisture levels can harm the fruits.
• Tomato fruits need warmth and moisture to swell and ripen. At the end of the growing season The period of time when an individual plant is in active growth. This will depend on the local climate and light levels, and can vary between different plants, although it is broadly from spring to autumn. ripening will slow down and fruits are best picked and ripened indoors in a warm dark place. At this time of year the nights are cool and day length is short with the sun lower in the sky. It is difficult to avoid conditions that lead to uneven ripening and fruit splitting or cracking.
• The increasing humidity The concentration of water vapour in the atmosphere. This affects the rate at which plants transpire (lose water from their leaf pores), which in turn affects how much water their roots absorb from the soil. If air humidity is low, plants transpire quickly and become at risk of wilting if water is lost from the leaves faster than it can be absorbed by the roots. Different plants require different levels of humidity to thrive. Many tropical houseplants need high humidity and are best grown in a steamy bathroom, misted regularly or placed on a saucer of damp pebbles. In a greenhouse, humidity can be raised in hot weather by damping down (wetting) the floor or overhead misting. as autumn approaches may also promote fungal moulds, especially grey mould (Botrytis cinerea). Splits and cracks will allow such fungi to enter and infect the tomato fruits.

Links

Grey mould

Control

Non-chemical control

• In the greenhouse or conservatory, control temperature and sunlight levels carefully to avoid extremes, using combinations of heating, ventilation The introduction of outdoor air into a space, for example, a greenhouse. This airflow can reduce temperature, replenish the gases absorbed by plants and keep down fungal diseases like grey moulds. and white greenhouse paint as appropriate. A good maximum-minimum temperature thermometer is essential. Poor quality greenhouses often lack adequate ventilation arrangements and temporary removal of glass panes during summer can help remedy this lack. Polythene tunnels have few options for decreasing the temperature except using extra shading or installing wind-up sides to increase ventilation.
• Managing temperature is almost impossible for tomatoes grown outdoors.
• Feed regularly to maintain high soil fertility. Special tomato fertilisers have high levels of potassium to encourage good fruit development.
• Water to maintain a constant level of soil moisture. This is especially important when growing in growing bags, pots or other containers. Outdoors, water to maintain as constant a level of soil moisture as possible. Plants grown in border soil, indoors or out, usually have a more extensive root system which helps protect them from fluctuations in water supply.

Chemical control

As fruit splitting and cracking is a physiological rather than a pest or disease problem, there is no point in using pesticides Pesticides are substances designed to kill or control the growth and behaviour of living organisms. They are also known as plant protection products and include insecticides, fungicides, herbicides and molluscicides. The RHS doesn’t support the use of pesticides and recommends that gardeners use non-chemical control options whenever needed. to treat the problem. There are no chemical controls.

Image: © GWI/Martin Hughes-Jones. Available in high resolution at www.gardenworldimages.com

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