Pruning concepts and practices for tropical fruit crops in the home landscape Jonathan H. Crane,...

Pruning concepts and practices for tropical fruit crops in the

home landscape

Jonathan H. Crane, Tropical Fruit Crop Specialist

University of Florida, IFASTropical Research and

Education Center, Homestead

Pruning outline

• Tree morphology and branch anatomy

• When to prune• Tree training• Tree size control• Rejuvenation of large trees

Tree morphology

• Morphology – the branch of biology that deals with the form and structure of animals and plants.

• Woody trees:– growth habit– branching patterns and models– branch anatomy

Growth habit classification

• Vigorous vs non-vigorous– Guava (vigorous) vs mamey sapote

(nonvigorous)– ‘Mauritius’ lychee (vigorous) vs ‘Kaimana’ lychee

(nonvigorous)

• Upright vs spreading– ‘Lula’ avocado (upright) vs ‘Booth 8’ avocado

(spreading)– ‘Tommy Atkins’ mango (upright) vs ‘Keitt’

mango (spreading)– ‘Arkin’ carambola (upright) vs ‘Kary’ carambola

(spreading)

Growth habit classification

upright spreading

Fruiting patterns and new vegetative growth

• Some fruit trees produce their fruit at the ends of the branches. New vegetative growth occurs from lateral buds.

• Examples: mango, lychee, longan

terminalflowering+ fruiting

lateral meristems

Fruiting patterns and new vegetative

growth

lateral flowering + fruiting

•Other fruit crops bear their fruit along the branches. New vegetative growth occursfrom the ends ofbranches (apical) and laterallyalong branches.•Examples include avocadoand sapodilla.

Fruiting patterns and new vegetative

growth•Still others may produce fruit terminally and along laterals (e.g., carambola) and on large branches (jackfruit). New vegetative growth may be from the terminal or along lateral branches.•Examples include carambola,jackfruit, and guava.

Branch anatomy

• Branch collars – branch collars are rings of wood with living cells about the bases of branches. This ring of living tissue provides the best wound response to a pruning cut and will callus and heal relatively quickly.

Bark ridges• The branch bark ridge is usually identified by

its rough ridge between two branches or a branch and the trunk. It indicates how strong the branches or branch and trunk are attached to each other. If the attachment is weak, the ridge is sunken like a valley between two mountain ranges; if the attachment is strong, the ridge sticks upward like the peaks of a mountain range. The attachment that is sunken is termed “included” – this means the bark interrupts the wood attachment between the two branches or trunk. A branch with an included (bark interruption) attachment is weak and subject to breakage much more than a branch with a complete (sound) wood attachment.

Bark ridges

Included bark,incomplete woodattachment

Complete woodattachment, strong

bark

wood

Bark ridges and included bark

Included bark,incomplete woodattachment, weak

Complete woodattachment, strong

woodbark

bark ridge

When to prune• In general we recommend pruning tropical/subtropical fruit

trees as soon after harvest as possible. This enables regrowth (1-2 vegetative flushes) to occur and mature before winter dormancy. A period of dormancy is needed in order for many tropical fruit crops to flower (e.g., mango, lychee, longan).

• Some varieties of avocado bear fruit late fall and winter making when to prune more difficult. In those cases, pruning every 2nd or 3rd year or only ½ the canopy any one year is recommended.

• Guava may have spring and fall fruit (some fruit all year) and carambola may have fruit during fall and winter. We recommend periodically pruning part of their canopy during spring or summer to allow for some regrowth before cool temperatures set in during the fall/winter months.

Types of pruning• Tree training refers generally to young trees

and is designed to guide young tree growth to form a strong tree framework for future heavy fruit production and good fruit quality.

• Tree size control refers to limiting tree size and generally refers to mature trees and may be accomplished by mechanical and/or hand-pruning methods.

• Rejuvenation refers to re-establishing and/or re-invigorating large to very large nonproductive and/or no-longer vigorous trees.

Tree training• Is usually

accomplished during the first 3 years after planting.

• Is used to produce a strong tree frame (structure) that can withstand heavy fruit loads and strong winds.

• Is designed to form a tree which may produce large crops of high quality fruit.

• Is also used to form a tree canopy with optimum light penetration into the canopy, and form a tree that is easier to care for, i.e., better penetration of needed foliar sprays and easier to harvest.

• Is generally done at or soon after planting; planting is best during the growing season when danger of freezing temperatures is minimum.

Tree training

• There are numerous types of tree designs trees may be trained to.

• Two of the most common include open center (vase) and modified central leader.

• Examples of open center – annona, carambola, mango.

• Examples of modified central leader – avocado, mango, mamey sapote, canistel.

• For some tree species, training trees to conform to a particular form may not be necessary nor necessarily desirable e.g., lychee, longan, lime.

• For these trees removal of poorly formed crotch angled limbs, poorly placed limbs, and stimulation of multiple branching is desirable.

Open-center3-4 ft

At planting, cut to 2 ½ to 3 ft ht and then select to 3-4 well spaced limbs with wide crotch angles around the trunk

3-4 ft

Aerial viewafter regrowth

Side view after regrowth

1-2 ft before first limb

Usually 4-8 inches between limbs 40o- 80o

Modified central leader3-4 ft

If at planting there are no lateral shoots, then cutback 6-12 inches to stimulate later branching

3-4 ft

3-4 ft 3-4 ft

If at planting there are lateral shoots, then select those spaced around the trunk and with a wide crotch angle, remove all others; remove central leader

Too narrow,remove

1-2 ft before first limb

Modified central leader

3-4 ft Remove central leader to nearest wide-angledlateral shoot

Remove limb with narrow crotch angle

3-4 ft The idea is to select 4-7 well spaced majorscaffold limbs with wide crotch angles Side view

Aerial view

1-3 years later

Pruning cuts• Heading back – a pruning cut

that only removes a small portion of a shoot. This is commonly used to force later bud break (branching).

• Thinning out cuts – complete removal of a limb (or shoot) to their point of origin– Reduces crowding– Results in less vegetative

regrowth than heading back

– Helps to limit tree size

• Cutting back – pruning back terminal lateral shoots to existing lateral shoots or branches– Reduces

crowding– Redirects

growth– Stiffens existing

shoots and branches

Maintenance pruning• After 2-3 years the

main training to obtain a particular form should be complete.

• However, depending upon the species periodic or annual pruning will be necessary

• For all species it will be necessary to periodically remove unwanted limbs and shoots (e.g., crossed, poorly placed, water sprouts).

• On mature trees, it may be desirable to periodically remove selected limbs (called thinning-out cuts) in order to – maintain light and air

movement on the inside of the tree canopy

– to reduce canopy wind resistance and

– to limit tree size.

• Best done during the growing season, usually after harvest, or early spring for late season bearing trees, or periodically as needed.

Tree size control• Is used to

– maintain trees to a desirable height

– maintain the lower canopy and lower canopy fruit production

– reduce shading of adjacent trees

– reduce toppling or uprooting during high winds

– improve light and air movement, thus improving fruit quality and reducing pest problems

• May be accomplished by hand pruning using thinning out and cutting back pruning.

• May be accomplished with only 1-5 pruning cuts per year or periodically.

• Best done during the growing season, usually after harvest, or early spring for late season bearing trees, or periodically as needed.

Tree size control• Prior to performing any

major pruning on large trees in the landscape, contact the local government for information on any ordinances specifying what may or may not be done to large trees. Some counties prohibit severe pruning of any large trees without a permit.

• May be labor intensive when done by hand.

• May be difficult on very large trees.

• May be accomplished by hand pruning or use of power pole saws and chain saws.

• Should be planned carefully and conducted judiciously as saws and power equipment may be dangerous if not used properly or one becomes tired.

• May best be done by a professional – be sure whoever you hire is a professional and has proof of insurance.

Why do you need tree size control

Lost productive canopy

Shade and lost branches

Possible danger

I can’t reachthe fruit!

Crash!!

fruit

Rejuvenation Possible purposes –• To re-establish fruit producing canopy

nearer the ground where it is easier to care for and harvest.

• To reduce the potential for toppling or uprooting or breaking apart during high winds and storms.

• To reduce the potential for causing harm to structures and people.

• To top-work to a new cultivar.

Rejuvenation - considerations• Safety – many times it

is dangerous for inexperienced people to attempt to drastically prune very large old trees. A professional arborist should be consulted or hired to do the job safely. Be sure he/she has insurance and you get everything in writing!

• Your purpose – are your fruit trees for fruit or primarily as shade?

• If for shade then tree size reduction does not need to be as drastic as for re-establishing the tree canopy for fruit production.

• Recommend doing this during early spring (after danger of freezing weather) but before hot summer and cool-cold fall/winter.

Rejuvenation• Scenario –

– 40 ft tall mango tree– Wanted for fruit

production• Recommendation –

– Selectively remove limbs to bring the tree height down by 1/3 to 1/2, open canopy to light and reduce wind resistance

– or hat-rack or stump to 10-15 ft (make sure this is legal in your area) and after regrowth use selective pruning to maintain new canopy at or below 20 ft

• Scenario – – 40 ft tall mango tree– Wanted primarily for

shade, but some limbs are hanging over the home

• Recommendation – – Selectively remove

limbs to bring the tree down some, open canopy to light and reduce wind resistance

– or hat-rack to 15 to 20 ft (make sure this is legal in your area) and after regrowth, selectively prune to maintain new canopy at or below 30 ft

Rejuvenation - steps• Decide purpose of

tree.• Recommend doing this

during early spring (after danger of freezing weather) but before hot summer and cool-cold fall/winter.

• White-wash bark of the tree to the height at which it will be stumped or hatracked. Mix white latex paint 50/50 with water.

• Carefully remove limbs starting from the top down until desired height is reached.

• Do not water the tree until you see new growth commence; then apply small, frequent amounts of fertilizer during the growing season.

Rejuvenation - steps

• As new shoots emerge from the trunk and remaining major scaffold limbs, select 2 or 4 well oriented (and spaced) limbs, and remove all others – this may have to be repeated.

• During the first year, as these selected limbs reach 3 ft or so in length, head them back to encourage branching; repeat to build a bushy, more compact tree.

• Then maintain the size of the tree with periodic maintenance pruning; described previously.

Aerial viewSide view

An example of the structure of a rejuvenated avocado tree.

hatracked

Regrowth from hatracking

Topworking – changing the scion (top) to a new variety

• White wash and stump tree as described before.

• As new shoots emerge from the trunk and remaining major scaffold limbs, select 2 or 4 well oriented (and spaced) limbs, and remove all others – this may have to be repeated.

• Veneer graft new variety to new shoots from the trunk when ½-1 inch in diameter. After new shoot begins to grow, gradually remove rootstock vegetative growth. When new shoot is growing well carefully remove rootstock shoot down to new scion.

Topworking - steps

New shoots which have emerged from theold trunk

Topworking - steps

Close up of one of the newshoots selected for veneergrafting with a new variety

Topworking and veneer grafting

side view front view

•On the rootstock make a thin vertical cut, 2-3” long, with a second horizontal cut at a 45o angle at the bottom of the first cut

Veneer graftingscion withterminal bud(s)

scion withonly axillary buds

• Select a scion of the new variety with 2-3 buds and of similar diameter as the rootstock

Veneer grafting

•On the scion make a slanting cut on 1 side, equal in length to that on the root stock. Make a small angled cut at the base to match the notch on the rootstock

side view back view

Veneer grafting

• Set the scion in place on the RS making sure to line up the cambial layers on a least 1 side

rootstock

scion

Veneer grafting

•Wrap the graft in an upward spiral, starting below the graft to just above the graft; tie-off the tape

Top working and veneer grafting

Newly emerged growthof new variety

Top working and veneer grafting

Newly emerged growthof new variety. New growth wellhealed and vigorous; begin toremove top of the shoot veneer grafted on to by cutting it back.Cut here

Top working and veneer graftingNewly emerged growthof new variety is wellhealed and vigorous; remove top of the shoot veneer grafted on to by cutting justabove the veneer graft.Cut here

Old shoot

For more information

• UF-IFAS publications web site: http://edis.ifas.ufl.edu

• UF-TREC FruitScapes web site: http://fruitscapes.ifas.ufl.edu or www.fruitscapes.info

• UF-TREC: http://trec.ifas.ufl.edu• Fla. State Hort. Soc.:

www.fshs.org

Credits

• Author – Dr. Jonathan H. Crane, Tropical Fruit Crops Specialist

• Drawings – Jonathan H. Crane• This presentation is copyrighted,

2005 University of Florida, Institute of Food and Agricultural Sciences