Training and pruning
Training is carried out during the first three to five years of growth (Figure 1). The common forms for conventional orchards are central leader, open center or modified leader systems, and for intensive planting systems, Y type, dwarf pyramid, pillar, espalier, and spindle have been tested with success in China.
Pruning methods are determined by patterns of fruiting. Pruning can be done in both the dormant and growing seasons. Dormant pruning is done mainly to remove shoots that are incapable of producing fruit of suitable size and quality such as weak, diseased, pest-damaged and crowded shoots.
Summer pruning includes removing useless or crowded sprouted buds and new shoots and damaged and diseased shoots. Summer pruning has been shown to be very effective on young and adult trees.
The tree can be trained to a certain shape with or without a central leader by training permanent branches. In general, about six to eight primary branches are kept within a height of 3 to 5 metres and well spaced in all directions. Trees need to be pruned annually to enable the tree to bear a full crop.
In the first season after planting a grafted tree carry out first training pruning during the dormant season:
- Cut the dominant central leader shoot at about 50cm.
- Cut the next three top side shoots back to 1 to 2 buds long.
- Bend down horizontally any side shoots that are too upright.
- Cut other side shoots back to five or six buds. Only cut to length, never trim any of the lateral shoots coming off the side shoot.
Repeat this pruning strategy each year until the tree is about 3m high. Side shoots need to be monitored during the growing season and pulled down to horizontal if growing too upright. Side shoots that get too long need to be trimmed back as soon as possible to the preferred length. To slow upward growth, the top central leader should be cut at the preferred height during the growing season while the shoot is thin.
If the central leader stem gets too thick before cutting, it will likely reshoot with a new vigorous shoot. When side shoots (fruiting arms) get too thick and old, they will start to develop new strong shoots near to the main central leader, when this occurs it is a sign that the fruiting arm needs replacing. Cut the old fruiting arm back close to the main central leader, but at a point where a suitable new horizontal shoot has grown, this new shoot will become the replacement fruiting arm.
Until recently Chinese jujube was propagated primarily by root suckers in China. More farmers in China now graft or bud onto seedling rootstocks.
Tissue culture has successfully been used for propagation but commercial production by this technique is still under development due to the requirements on high skill and expensive facilities.
In WA trees are mainly propagated by budding or grafting. For more information see the page Propagating jujubes.