Training and pruning of fruit trees
Why and how fruit trees are trained and pruned, heading and thinning cuts, central leader and open centre systems, bearing habits, and a crop-load sum.
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Left alone, most fruit trees grow tall and dense, shade their own inner branches, bear heavily one year and lightly the next, and become hard to spray and harvest. Training shapes a young tree into a strong, open framework; pruning removes parts of the tree to maintain that shape, balance growth with fruiting and renew bearing wood. Together they decide how much light reaches the leaves and fruit, which in turn decides yield, fruit size and colour, and the cost of every operation in the orchard.
Training systems, pruning principles and the bearing habits of fruit crops are standard exam topics in pomology.
Training versus pruning
- Training directs the growth of a young tree, usually in its first three to five years, to build a strong framework of well-spaced scaffold branches with wide angles. It uses pruning, but also bending, tying, spreading and support systems.
- Pruning is the removal of shoots, branches, roots, buds, flowers or fruits throughout the tree's life to regulate growth, fruiting and health.
Objectives
- Build a strong framework that carries heavy crops without breaking.
- Let light into the canopy: fruit buds form, and fruits colour and size well, only in adequately lit parts of the tree.
- Balance vegetative growth with fruiting, and reduce alternate bearing.
- Remove dead, diseased, damaged and crossing branches, improving air movement and spray coverage.
- Keep trees at a size that suits the orchard system and machinery.
How trees respond to cuts
- Heading cuts remove part of a shoot, cutting back to a bud or a stub. They release the buds below from apical dominance and produce several vigorous shoots near the cut, making the tree denser.
- Thinning cuts remove a whole shoot or branch back to its point of origin. They open the canopy without stimulating much regrowth.
- Dormant (winter) pruning of deciduous trees stimulates vigorous growth in spring; summer pruning removes leaf area and slows growth, and improves light to fruit.
- Heavy pruning delays bearing in young trees; light, careful training brings them into bearing earlier.
- Horizontal or bent branches grow less vigorously and flower more than upright ones; this is why spreading branches with weights, ties or spacers is part of training.
Training systems
- Central leader: one dominant, upright leader with tiers of scaffold branches, giving a pyramidal tree that lets light into the lower branches. Traditional for apple and pear; modern spindle and tall spindle systems are slim central-leader trees on dwarfing rootstocks planted at 1,000 to 3,000 or more trees per hectare.
- Open centre (vase): the leader is removed early and three or four main scaffolds form a bowl with a sunny centre. Used for peach, nectarine, plum, apricot and many mango and guava orchards, especially in sunny climates.
- Modified leader: the leader is kept for a few years to build scaffolds, then cut back; a compromise between strength and light.
- Trellised and planar systems: espaliers, palmettes, V- and Tatura trellises, and fruiting walls, which make thin, two-dimensional canopies that are easy to light, spray and harvest, and suit mechanisation.
Vines have their own systems. Grapes are trained to bower (pergola), head, cordon and trellis systems, and pruned to spurs (short, two- to three-bud stubs) or canes (longer one-year shoots), depending on where fruitful buds sit in each variety.
Bearing habit decides how to prune
Pruning must keep the kind of wood on which the crop is borne:
| Crop | Where fruit is borne | Pruning implication |
|---|---|---|
| Apple, pear | mainly on spurs on two-year and older wood, also some terminal buds | keep and renew spurs; avoid heading all shoots |
| Peach, nectarine | on one-year-old shoots | renew fruiting wood every year by fairly heavy pruning |
| Plum, cherry, apricot | on spurs and one-year shoots | moderate pruning, renew older spurs |
| Grape | on current season's shoots arising from one-year canes | prune canes or spurs to a set number of buds each year |
| Citrus | on current growth flushes, terminal and axillary | light pruning: remove dead wood, water shoots, crowding |
| Mango | on terminal shoots of mature flushes | light pruning after harvest; tip pruning to time flowering in some regions |
| Guava, ber | on current season's growth | annual pruning promotes new fruiting shoots |
| Fig | on current growth and one-year wood | depends on the crop type |
Other forms of pruning
- Pinching (removing soft shoot tips), disbudding and deshooting.
- Thinning of flowers and fruits: reduces crop load to improve fruit size and quality, and lessens alternate bearing.
- Root pruning: cutting roots to slow vegetative growth and encourage flowering.
- Rejuvenation pruning: heavy cutting of old, unproductive trees, such as senile mango orchards, to regrow a productive canopy over two to three years.
Good practice
- Use sharp, clean tools; disinfect them between trees when diseases such as fire blight or cankers are present.
- Make cuts just outside the branch collar and avoid leaving long stubs, so wounds close properly.
- Prune in dry weather to reduce infection; burn or remove diseased prunings.
- Prune lightly and regularly rather than heavily at long intervals.
Setting crop load by trunk size
Apple growers often set crop load as fruits per square centimetre of trunk cross-sectional area (TCSA), measured 20 to 30 cm above the graft union. A common target for many varieties is about 6 fruits per cm2.
A young tree has a trunk circumference of 20 cm.
- Radius = 20 ÷ (2 × 3.1416) ≈ 3.18 cm.
- TCSA = 3.1416 × 3.182 ≈ 31.8 cm2.
- Target crop = 6 × 31.8 ≈ 190 fruits.
If the tree has set 450 fruitlets, about 260 must be removed by hand or chemical thinning. At 1,500 trees per hectare and an average fruit of 200 g, 190 fruits per tree give about 1,500 × 190 × 0.2 = 57,000 kg, or 57 t/ha.
Key points
- Training builds the framework of young trees; pruning maintains shape, light, balance and health.
- Heading cuts stimulate dense regrowth; thinning cuts open the canopy.
- Dormant pruning invigorates; summer pruning slows growth; bent branches flower more.
- Systems: central leader (apple, pear, spindles), open centre (peach, plum, mango), modified leader, trellises; grapes pruned to spurs or canes.
- Pruning must keep the fruiting wood: spurs in apple, one-year shoots in peach, current shoots in grape, terminals in mango.
What the exams ask
- School-leaving and entrance papers: definitions and objectives of training and pruning, and examples of training systems.
- Degree and research-fellowship entrances: heading and thinning cuts, apical dominance, bearing habits of fruit crops, training systems and their suitability, rejuvenation of old orchards, and crop regulation.
- Professional examinations: pruning programmes for specific crops, high-density systems, and crop load management.
Described in general terms: the kind of examination, not a past paper. Laisha never reproduces exam questions.
Questions people ask
Why does heavy winter pruning make a tree grow more?
The roots and their stored reserves stay the same while the number of buds falls, so each remaining bud receives more resources and grows vigorously. Excessive vigour reduces flowering.
When should I prune mango?
Usually right after harvest, removing dead, diseased and crowded branches and opening the centre. Heavy pruning before flowering removes the terminal shoots that would bear the next crop.
Should pruning wounds be painted?
Large wounds on some species benefit from protection where diseases are a problem, but on most trees a correct cut outside the branch collar heals well without paint.
Sources
- Westwood, M. N. Temperate-Zone Pomology: Physiology and Culture, 3rd edition. Timber Press, 1993.
- Ferree, D. C. and Warrington, I. J. (eds) Apples: Botany, Production and Uses. CABI, 2003.
- Tromp, J., Webster, A. D. and Wertheim, S. J. (eds) Fundamentals of Temperate Zone Tree Fruit Production. Backhuys Publishers, 2005.
- Jackson, J. E. The Biology of Apples and Pears. Cambridge University Press, 2003.
- Chadha, K. L. (ed.) Handbook of Horticulture. Indian Council of Agricultural Research, latest edition.
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