Pruning & trellising of tomato plants to optimise greenhouse production

Shaping tomato plants can be done by pruning and trellising plants with indeterminate growth habit. This will enhance air circulation and ventilation, optimize space and sunlight, improve growth balance between roots, leaves and fruit, and optimize the working space.

Advantages of shaping the tomato plant

1. Reduces the incidence of physiological disorders e.g. fruit cracking and the uneven ripening of fruit due to exposure to high solar radiation and high temperature 2. Reduces the incidence of fruit rot and soil-borne diseases 3. Maximizes the efficiency of photosynthesis 4. The upright plants have fewer disease problems with leaf spots and fruit rots because their leaves stay drier and are not in contact with pathogen laden soil.

Disadvantages of shaping the tomato plant

1. Requires expertise (good management and skilled workers) 2. Trellising and pruning need to be done regularly – labour intensive 3. Plants can be damaged during training and harvesting. Pruning is simply the removal of the side shoots or suckers which develop between the main stem and the leaf. It helps to maintain a balance between vegetative and reproductive growth. Generally, if you do not prune or prune few side shoots, your plant will show excessive vegetative growth which may result in smaller fruit size. Care should be taken not to prune the growing point of the main stem otherwise your plant will stop growing and bearing fruit. Suckers can be removed with thumb Sucker/ side-shoot and forefinger by pulling outwards. They are removed while they are young and succulent (2 to 5 cm long) when they heal faster. Large suckers are not easily removed and can create a larger wound, which takes time to heal and can be an entry point for pathogens. there is a high reduction in 10

Experimental evidence has shown that

Growing-point

Side-shoots

Prun ing & tr ell ising of t omat o plants 9

yield when side shoots are allowed to develop 15-20 cm in length because they use nutrients which should go into fruit development. When working with big-suckers, it is important to remove the growing point of the sucker, causing less shock to the plant. Removing big suckers may necessitate using a knife, shears or scissors. It is important to disinfect the instrument after cutting to prevent diseases being spread from one plant to another. Pruning of suckers is known to increase the size of the fruit and promotes early harvesting. Determinate cultivars are not supposed to be pruned, but the leaves below the first truss can be removed to enhance air circulation. Pruning does not affect the fruit size or the vegetative growth of determinate cultivars if pruning is done below the first truss. Pruning of Removal of the older leaves results in trusses facing towards the walkway, which makes suckers above the first truss will result harvesting easier. in lower yield. When the plant matures, especially the other hand. It is important not to Removing the growing points of a when the first two trusses have been remove the green leaves since they plant will stop growth and enhance harvested, lower leaves function as a source of fruit ripening. With approaching low turn yellow. Generally, Water should be food supply to the fruits. temperatures (frost), it is important remove yellow leaves chemically analysed in The figure below shows to prune the growing points of all below the ripening fruit clusters. These yellow leaves should be snapped off with fingers and order to determine the levels of the different nutrients in solution. how a plant should look after removing the old leaves. Old leaves should be removed far the plants. This is because tomato is sensitive to low temperatures, so by removing the growing points will stop fruit bearing and ripening of fruits will removed as they are not In low rainfall areas, from the production be enhanced. actively photosynthesizing. In addition, this will enhance air circulation around the base of the plant, and will help to reduce fungal and bacterial disease build-up. This can be done by holding the main stem with one hand and snapping off the leaf where it is attached to the main stem using area and destroyed to prevent the spreading or build up of diseases. Indeterminate cultivars grow very tall, and with time the yield and fruit size become progressively smaller. high levels of salts are usually present. Trellising Trellising is done by tying twine from the bag to the stay wire above the plant. The stem is then twisted around the twine to give support. Trellising should be done two weeks after transplanting. If transplants are not trellised at early stage, they become crooked and trellising then will result in breaking or damaging the plant. Normally a tomato plant may grow approximately 5 – 6 m in a 6 month growing season. It is therefore important that the stay wires are strong enough to carry the mass of a whole row of plants with fruit. The total mass of the plants and fruit in a 45 m row is more than 1 ton. Therefore, considerable damage to plants will result if the stay wire breaks at the height of the production season. Source: ARC Vegetable and Ornamental Plant campus.