(subtitled) - universal principles of pruning and training fruit trees
NZ Tree Crops Association annual conference, Unitec, 15 April 2007
Reg Lewthwaite, Lecturer in Horticultural Science, School of Natural Sciences, Unitec
Reg Lewthwaite — Pruning Olives & Feijoa - Room 1, Sunday 9:30am
Reg is a lecturer at Unitec and has always been at the forefront of the horticulture industry. Now Reg has turned his attention to commercial olive and feijoa orchards. Reg believes that there is substantial room for production increases with a better pruning regime and was to explain how. Did he succeed? Damned if I know. Sure made us think, or confused. It's all about understanding the tree's needs and your needs, pruning for light, crop access and orchard servicing with minimum retardation of tree growth - as already emphasised by the great Dr. Don McKenzie and others. So why are so many text books and teachers still promulgating so much unnecessary tree and crop damage?
First – select a suitable site for the selected plant:
The soil must have
- Aeration = drainage + open soil
- Water = irrigation
- Food = nutrients
A Unitec feijoa trial in 2006/7 gave a fruit weight increase of
- High irrigation 22%
- High fertiliser 24%
- Combined increase 51%
Process
- Learn the botany of the tree — tree shape - olive is positive, feijoa is negative
- Pruning to produce the most economic crop
- Production – maximise production/ha
Botany
A tree has 3 bits -
- Shell canopy of a leaves/flowers/fruit
» about 20 - 30 cm deep in feijoa
» 60 - 90 cm in olive - Branches
- Trunk
1st principle
Light must penetrate through the tree
- The top catches most light = apical dominance
- Shaded branches go blind
2nd principle
Pyramid tree shape with
- One leader (or up to 4 vertical structural leaders)
- Picking bays = access, light, spray
- Pyramid shape captures light, down to lower tree
- Vase (an upside down pyramid) with open centre
» shades the lower part of the tree
» fruit can't be reached at harvest
3rd principle
Renewal pruning
- Euthanase old wood & let the light in
- Rejuvenate with moderate new branches
- Young wood has better quality fruit
- Uncut branches fruit earlier and heavier
- Never ever
(except for plants that flower on current wood)
» cut the ends off anything
» twig (spur) prune
4th principle
- Manage tree height
- Don’t worry about strong apical growth at the top of the tree
- Relax — panicking only makes it worse
- Periodically cut back into mature wood
Pruning
- Cutting slows overall growth — especially young trees
- The tree responds with apparent vigorous growth
- This new wood is non fruiting — it creates height and shade
- More and more wasteful cutting is needed
Production theory
Get canopy cover over the site ASAP
- The more leaves the better – only leaves catch the light, and make food for the crop
- Light on the orchard floor = wasted light = lighter crops
Lewthwaite, Reg Lecturer in Horticultural Science, GROWSAFE Trainer, School of Natural Sciences, UNITEC New Zealand
Email for contact details
Reg assisted Dr Don Merton and helped develop the high productive single leader apple tree form for the apple industry. Reg has looked at unkempt olive trees (19th Century, Logan Campbell olives at One Tree Hill) and found that most naturally grew in a single leader form.
Applying the same rational as apples of keeping most of the productive growth low and open (easy to harvest) Reg postulated that the Olive industry is under performing with the current pruning styles.