Revised 11/98 -- Author Reviewed 11/98 HIL-201-B
Effect on Plant Size and Crop Yield
Pruning a plant reduces its ultimate adult size and the crop
yield in at least the following season. To compensate for this loss
of bearing area and yield, other factors, largely economic, must be
considered in planning a pruning program.
Effect on Fruit Size
By reducing the number of fruit buds (and hence clusters) on the
bush, pruning results in an increase in the size of the individual
berries. Up to a point, the more severe the pruning, the larger the
remaining berries are. Pruning for increased size is a compromise
between desired size and yield (numbers) of fruit.
Effect on Ripening Period
Moderate to heavy pruning tends to shift the ripening period
forward so that most of the remaining fruit ripens together and
early. Light pruning results in a longer season of ripening. It may
be more profitable in southeastern NC to prune fairly heavily, even
at the expense of some yield, to realize the earliest possible
maturity.
Effect on Plant Growth and Vigor
Pruning results in longer and more vigorous (thicker) shoot
growth in the next season. Heavy pruning causes thicker and more
leafy shoots than light pruning. The thicker and later-developing
shoots tend to produce fewer fruit buds than those which stop growing
earlier in the season. Fruit of the blueberry is borne on wood
produced in the previous season (one-year-old wood). By pruning, you
are regulating the fruiting potential of next season's crop. Pruning
should be severe enough to invigorate the plant so that sufficient
new wood is produced during the following season. You are actually
determining the fruiting potential of the crop of two seasons hence
by the number and type of cuts you make this winter.
Spacing the Crop on the Bush
By wise selection of canes and lateral shoots on those canes
which will bear the crop, the grower can prune to have his fruit
well-distributed on the plant. Well-distributed clusters should have
enough leaves around them to provide adequate foodstuffs, but not
enough to overshade the fruit, or to reduce spray or dust coverage,
or to make the clusters hard to reach during harvest.
Bush Life and Productive Life
Blueberry bushes tend to overbear, which shortens their lives. By
pruning to regulate crop load, the grower can lengthen the life of
his bushes and increase the number of commercial crops.
When to Prune
Blueberries should be pruned during the winter while the bushes
are dormant. In winter, flower buds are easily visible on
one-year-old wood and their numbers can be adjusted by pruning to
regulate the crop load for the coming year.
Tools Needed
Most blueberries are hand pruned using long-handled pruning
loppers capable of cutting branches 2 to 3 inches in diameter. Finer,
more detailed pruning such as thinning of flower buds on individual
fruiting twigs requires smaller, one-hand pruners. For larger
plantings, pneumatic pruners are available, but these tools require
an air compressor and are fairly expensive.
Training Young Plants (1 to 3 or 4 Years of Age)
If vigorous, well-rooted two-year-old plants are set, they do not
need cutting back the first year in the field except to remove fruit
buds shortly after planting. Pruning should be moderately heavy in
the second year in the field to stimulate strong new growth on
selected canes. Do not permit plants younger than three years of age
to bear more than a cluster or two of fruit, or the onset of the
commercially productive period will be delayed. A large bearing area
should be established in the shortest possible time.
Pruning Bearing Plants (over 3 to 4 years of age)
Renewal Pruning
When blueberries are about 8 to 10 years old, they are at their
productive peak, but renewal growth has reached a minimum, and
production will then decline markedly from year to year. Some
provision must be made to revitalize the plant to prolong its
productive period. Weak or badly diseased canes should be removed
entirely. These canes can be identified by generally poor vigor and
low fruit bud production. However, eastern NC many varieties do not
sprout new canes readily from the crown. It may be necessary to
either cut the cane back to a strong lateral which is properly
located, or to cut the cane severely ("dehorn") back to within 2 to 3
ft of the ground. By the latter method, it is hoped that new lateral
branches can be forced from below the cut.
Either method may result in a 1- to 3-year crop reduction, but the plants should then bear several more good crops. However, when rejuvenation becomes necessary, it is well to start considering newer and better varieties to which your acreage may be systematically replanted in the near future.
North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.