1. Pruning concepts and practices for tropical fruit crops in the home landscape Jonathan H. Crane, Tropical Fruit Crop Specialist University of Florida, IFAS Tropical Research and Education Center, Homestead

2. Pruning outline Tree morphology and branch anatomy When to prune Tree training Tree size control Rejuvenation of large trees

3. 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

4. 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)

5. Growth habit classification upright spreading

6. 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 terminal flowering + fruiting lateral meristems

7. Fruiting patterns and new vegetative growth lateral flowering + fruiting Other fruit crops bear their fruit along the branches. New vegetative growth occurs from the ends of branches (apical) and laterally along branches. Examples include avocado and sapodilla.

8. 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.

9. 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.

10. 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.

11. Bark ridges Included bark, incomplete wood attachment Complete wood attachment, strong bark wood

12. Bark ridges and included bark Included bark, incomplete wood attachment, weak Complete wood attachment, strong wood bark bark ridge

13. 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 2 nd or 3 rd 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.

14. 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.

15. 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.

16. 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.

17. Open-center 3-4 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 view after regrowth Side view after regrowth 1-2 ft before first limb Usually 4-8 inches between limbs 40 o - 80 o

18. Modified central leader 3-4 ft If at planting there are no lateral shoots, then cut back 6-12 inches to stimulate later branching 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

19. Modified central leader 3-4 ft Remove central leader to nearest wide-angled lateral shoot Remove limb with narrow crotch angle 3-4 ft The idea is to select 4-7 well spaced major scaffold limbs with wide crotch angles Side view Aerial view 1-3 years later

20. 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

21. 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.

22. 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.

23. 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.

24. Why do you need tree size control Lost productive canopy Shade and lost branches Possible danger I can’t reach the fruit! Crash!! fruit

25. 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.

26. 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.

27. 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

28. 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.

29. 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 view Side view

30. An example of the structure of a rejuvenated avocado tree. hatracked Regrowth from hatracking

31. 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.

32. Topworking - steps New shoots which have emerged from the old trunk

33. Topworking - steps Close up of one of the new shoots selected for veneer grafting with a new variety

34. 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 45 o angle at the bottom of the first cut

35. Veneer grafting scion with terminal bud(s) scion with only axillary buds Select a scion of the new variety with 2-3 buds and of similar diameter as the rootstock

36. 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

37. 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

38. Veneer grafting Wrap the graft in an upward spiral, starting below the graft to just above the graft; tie-off the tape

39. Top working and veneer grafting Newly emerged growth of new variety

40. Top working and veneer grafting Newly emerged growth of new variety. New growth well healed and vigorous; begin to remove top of the shoot veneer grafted on to by cutting it back. Cut here

41. Top working and veneer grafting Newly emerged growth of new variety is well healed and vigorous; remove top of the shoot veneer grafted on to by cutting just above the veneer graft. Cut here Old shoot

42. 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

43. 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