Flower buds are produced on the end of a shoot's growth. The flower buds are plump and rounded, leaf buds are small and pointed. Each flower bud may produce a cluster of five to eight berries. If all flower buds are left on, too many berries will be produced and many will be small and worthless. Also, short thin shoots will grow, resulting in poor fruiting wood for the following year's crop. Bushes need little pruning during the first two or three years after planting; only short, weak twiggy growth need be removed.
After two summers in the field, all the plants should be ready to prune for a small crop (1/2 to 1 pint per bush). Remove the thin, twiggy growth and concentrate the potential crop on a small number of stout, fruiting shoots. By limiting the cropping to only the strong shoots, the bush will continue to grow rapidly. A heavy crop at this time dwarfs the bush.
Pruning Mature Bushes
After the fourth summer in the field, some canes may show a weakening due to heavy bearing. From this time on, the first step in pruning is to remove canes which have only small weak, fruiting twigs. They may be cut to the ground or to a strong side shoot near the ground. This will stimulate the sprouting of new canes from the base, which keeps a plant relatively "young." It also allows adequate sunlight to penetrate the bush and promote the setting of fruit buds.
With enough sunlight, the new canes will start producing fruiting laterals in the second year at a relatively low level in the bush and will be able to develop a large zone of fruiting wood in the third and fourth years. In a dense, crowded bush, a new cane will take three or four years to produce nothing more than a tuft of fruiting twigs at the very top of the bush.
The number of old canes to be removed depends on the rate of growth over the past several years and varies considerably over six years old, it may be necessary to remove two canes annually, due to changing growth rates.
After removing the older canes, the small twiggy growth is eliminated in favor of the stronger shoots. A limited amount of twiggy growth may be left in the lower portion of the bush. At this level shading is not a factor, and the fruit production from these twigs will add to the total crop.
Pruning Weakened Bushes
Blueberry bushes are often weakened by:
- overbearing due to improper pruning
- poor soil drainage
- insufficient fertilizer
- drought injury
- scale injury
- grubs feeding on the roots
After the undesirable conditions have been corrected, it is possible to rejuvenate the plants by removing 1/3 to 1/2 of the old bush. This is accomplished by making large cuts at ground level. The remaining portion of the plant is allowed to bear heavily. The remaining old canes are removed the following spring.