Plant Manipulation On Tree Crops

Trellising and pruning are used to:

• Maximise the ability of the plant to produce a crop.
• Create a shape that is ideal for harvesting.
• Allow the plant to be directed in a manner that maximises light and encourages fruiting.
• Make it easier to control diseases and pests.
• To produce better quality plant and to extend the life of a plant.
• Allow plants to fruit earlier.

Pruning

Plants are pruned primarily to encourage growth of new flower bearing wood, to remove dead vegetation and to improve their appearance or to keep a tree at a manageable size, making harvesting more efficient. Pruning is only done on perennial scrubs and trees.

In a natural environment pruning occurs through the action of wind, or through breakage due to excessive fruit loads, and animal browsing. Such natural pruning frequently leaves stubs or slowly healing wounds that are susceptible to decay and disease.

Pruning in orchards prevents decay at broken areas and promotes quick healing of wounds.

The major pruning tools that are used in tree crops are pruning shears and a specialised saw called a lopper. In some cases, specialised motorised saws can also be used. Depending on the size of the trees a chain saw can also be used. The principals of pruning as described below are the same independent of the tools used.

It is important that the tools used are always kept clean and free of plant residues. They should also be sharpened regularly. This will ensure that the pruning cut is always clean and accurate.

Pruning is mostly done during the dormant period (winter) although summer pruning can also be done.

The basic rules for pruning are:

• Remove all dead wood.
• Remove damaged wood such as scales or sun scalded wood or wood covered in lesions.
• Remove branches that cross the centre of the plant, or those that rub against other branches.
• Remove suckers completely.
• Remove branches that make the bush look lopsided.
• Remove an old cane for each new cane that develops. This will renew the plant.
• The cane should be cut back to an outside but eye about the fourth bud eye or so from the base.
• The cuts should be clean and at a 45-degree angle to the stem. Ensure the pruning shears are sharp and clean before use.

Click here to view a video that explains how to prune trees

Click here to view a video that explains how to prune fruit trees the right way every time.

Training and Trellising

Training and trellising systems are not only used in vegetable crops, but also in some fruit tree crops. During the initial stages of plant development, the farmer is mainly concerned with the training of the tree. The aim is to develop a framework for the future that can carry heavy crops of good-quality fruit.

Click here to download a handout that explains training tree crops (Apple).

Click here to download a handout that explains training vegetable crops

Click here to view a video that explains Pruning a grapevine.

Click here to view a video that explains Pruning a grapevine.

Fruit Ripening

The process of fruit ripening can be encouraged using chemicals. A compound for examples such as Ethephon can be used to induce even ripening in tree crops. In crops such as macadamia and walnuts, the compound is used to ensure even nut drop, making the harvest easier.

In some crops such as blue berries and cherries, bud break will only occur after the crops have experienced significant cold spells. Should insufficient cold be experiences, the crop will not bud and low yields will be experienced. To this end chemicals such as HCN are used to induce bud break.

Pollination

Pollination is important for fruit set in all fruiting crops. In most cases bees are the preferred pollinators. Where natural bee populations are low, beekeepers are employed to supply hives to orchards. Where bees are important for pollination it must be ensured that spray programmes are developed to ensure the bees populations are not damaged through pesticide applications.

In the case of hydroponics crops, most pollination occurs through ventilation, insects or movement of workers through the glasshouses. In crops such as peppers, pollination is critical and manual pollination may be necessary. Vibrating the stay wires on the trellising shakes the plant which aids pollination.

Thinning

Thinning is a manipulation process by which a part of a too heavy crop is removed. This leads to improved fruit size and promotes regular cropping by alleviation of alternate bearing.

Thinning should be carried out early in the season, after the first natural fruit shed and as soon as it becomes obvious that the crop will be too heavy. After thinning make sure that mature fruit are not in contact with each other.

If fruit trees can produce a too heavy crop, the tree will produce a crop only every second year (alternate bearing). Thinning will ensure that the tree produces a crop every year.

Thinning can also be done during pruning by thinning out bearer shoots. In tomatoes and cucumbers grown under protection, thinning implies the removal of all lateral branches, leaving one bearing stem only.