HORT 413 Tree Fruit Production

Orchard systems

• cultivar
• rootstock/interstock
• tree spacing
• training system
• tree support system
• pruning
• tree arrangement
• environment
• soil

Aim: To optimize productivity and efficiency by matching all the components of the orchard system

Productivity - closely related to light interception. Tree spacing and shape important. Management of young trees to fill their space quickly. Higher density plantings

Efficiency - harvest index strongly influenced by rootstock. More dwarfing rootstocks generally partition more carbohydrate to the fruit at the expense of wood.

Characteristics of a good planting system

• fills allotted space quickly

• precocious

• high light interception

• minimize proportion of tree canopy with <30% full sunlight

• good balance between vegetative growth and fruiting

• allow access for orchard operations

• allow good penetration of pesticide applications

• efficient management

Branch angles

Upright - vegetative

Horizontal - fruitful

Branch angle also has major implications for light penetration and strength of branch attachment.

Light

Require good light penetration to fruiting sites for:

• · fruit bud initiation

• fruit set

• fruit size

• fruit color

• fruit quality

Ensure good light distribution throughout tree canopy by

• large surface area/volume

• light textured canopy

How much light is required?

Photosynthesis saturated at about 800 umol.m-2.s-1

About 30% of full sunlight.

Reasons for pruning

• to remove broken, diseased or insect-infested branches

• to control tree size, height and branch spread, alleviate crowding, and facilitate orchard operations

• to improve light exposure of bearing surface to maintain fruitfulness and improve fruit quality

• to stimulate vegetative growth in trees, or parts of trees, that are low in vigor

• to remove weak bearing wood that is only marginally productive and that produces fruit of poor quality

• to remove excessively vigorous, unproductive wood that creates shade

• to renew structural units of declining fruitfulness

• to improve insect and disease control by ensuring effective penetration of plant protective sprays

Trees planted too close - overcrowding, low productivity poor fruit quality, management problems

Trees too widely spaced - reduced light interception and lower productivity potential.

Pruning physiology

Concept of shoot:root ratio. Following normal dormant pruning, root growth slows or ceased, while rapid shoot growth to re-establish equilibrium.

Shoot growth response is localized.

Pruning young trees delays cropping - minimize pruning until year 3-4.

Root pruning - reduce root mass followed by reduced vegetative growth.

Vegetative/fruiting balance - enough vigor for fruiting wood renewal, but not excessive.

Pruning is a dwarfing practice - the pruned tree will be smaller than the unpruned tree. Growth response is insufficient to compensate for wood removed.

Time of pruning will affect the response

Dormant

• usual time for pruning fruit trees - Feb, March, later for peaches.

• cold injury may be increased

• localized growth response

• least dwarfing of all pruning times

Summer pruning

• more dwarfing effect
• after terminal bud set
• usually to enhance fruit color
• only on mature trees
• may reduce fruit size

Root pruning

• carried out at full bloom
• reduces vigor
• increased fruit firmness, soluble solids concentration
• reduced pre-harvest drop
• reduced fruit size

Types of pruning cut

Heading cut - localized growth response

Thinning cut - more general growth response

Renewal pruning - remove older wood leaving younger fruiting wood:

• stronger spurs leading to larger fruit
• tends to be in a better light environment
• higher fruit quality
• 'recycle' ends of branches

Remove "droppers"

Mostly thinning cuts, keeping heading cuts to a minimum.

Concentrate on overall tree structure - make a few large cuts, rather than lots of snipping (different growth responses).

Growth habit

Before pruning, the fruiting/bearing habit of the crop must be understood. Applies to different crops and even different cultivars.

Apple growth habits can be divided into 4 types

1. Strongly basitonic, spur type. Limbs have strong apical dominance, short lateral shoots (spurs) on wood 2 years and older. Narrow limb angles. U-shaped tree form eg, spur 'Red Delicious'

2. Somewhat basitonic - limited side branching, strong apical dominance. Slightly wider limb angles eg, standard 'Red Delicious', 'McIntosh'

3. Somewhat acrotonic - fruit on spurs and terminal buds. Good branching without pruning eg, Gala, Golden Delicious, Jonagold

4. Strongly acrotonic - Upright growth, tip bearers, branching and fruiting near terminal ends of branches. Often have blind wood. Weeping or umbrella tree form. eg, Rome, Granny Smith, Fuji

The particular growth habit must be taken into account prior to pruning.

Apples, pears, cherries - generally fruit on wood 2 years old and older

Peaches - fruit on one year-old wood

Fruit tree training systems

• Center leader types &endash; French axis, slender spindle, slender pyramid, hytec
• Palmette
• Tatura trellis, V and Y trellis
• Lincoln canopy
• open center (vase)

Tree supports, using a trellis system or individual tree stakes - may result in more rapid canopy establishment, but high cost.

Developing a center leader tree (apples, pears, cherries)

Planting

Plant a good quality tree - preferably branched

Head back to 30-36 inches

Remove lateral branches below 24 inches

Head back lateral branches if they are strong

1st season

Select new leader in summer and eliminate competing shoots

Spread lateral branches to improve crotch angles using clothespins, toothpicks, spreaders, ties, or weights. Narrow crotch angle are weak and may break out

Select 4-6 lateral branches for permanent first tier and remove other competing shoots - the earlier the better

The only summer pruning should be the pinching out of unwanted branches

2nd season

Maintain leader dominance by removing competing shoots

Head back leader if required

Select and position first tier scaffold branches - spaced out along the trunk 6-8" apart, and at 30-45° above the horizontal plane

Head selected scaffold branches if their growth has been excessive, or if the cultivar normally bears few side branches

3rd season

Maintain leader dominance

Develop secondary fruiting branches at least 2 feet above bottom scaffolds

Spread secondary branches if they are upright and/or growing strongly

Emphasize training rather than pruning

4th season and later

Maintain conical shape (like a Christmas tree) and open framework by:

• keeping lower scaffolds larger and wider than the top of the tree
• keep top of tree slender - remove branches in the top half of the tree before they get too strong and create too much shade
• using thinning pruning cuts to space branches out along the trunk
• create space between branches by eliminating droppers