Pruning-Blueberrries-25JAN14.pdf

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Pruning Blueberries
Bill Cline, Plant Pathology Department, NCSU
Revised 25 Jan 2014
Cultivated blueberries are upright, deciduous, woody perennials, forming multi-stemmed
bushes with maximum unpruned heights varying from 6-8 feet (highbush, southern highbush)
to 10-15 feet (rabbiteye). All cultivated species require annual pruning to manage bush height
and shape. Pruning also prevents over-cropping, increases berry size, and removes dead,
diseased or insect-infested wood.
Pruning is second only to hand harvest in terms of annual labor expense. So how is pruning
accomplished quickly and economically, and what is the easiest way to explain pruning goals to
a crew of workers entering the field for the first time? The following teachable steps, in order,
can be used at each bush to rapidly eliminate undesirable growth, selecting for flexible, upright,
and productive canes.
Tools and Techniques
Most blueberry pruning is done during the dormant (winter) season after the leaves have
fallen. Mature canes can be up to two inches in diameter, so long-handled loppers capable of
cutting large stems are essential. Smaller one-handed pruners are used for finish work and for
shaping young bushes. Make flush cuts to avoid leaving stubs. Pruning cuts are not treated,
though some authorities recommend timing standard fungicide sprays to occur immediately
after pruning, especially when late spring and summer cuts are made on actively-growing
bushes.
Steps in Winter Pruning (November – March)
STEP ONE:
Define the crown. Pruning starts at the ground, not at the top of the bush. Visualize
a circle 12 to 18 inches in diameter around the crown of the bush, and remove ALL shoots of
any age that have emerged from the ground outside the circle. This narrows the base of the
bush to facilitate machine harvest, but is also a good general step for hand-harvested fields as
well.
STEP TWO:
Remove low-angled canes and crossovers. Low-angled canes that are too close to
the ground are undesirable because the fruit is more likely to contact the ground, or to be
contaminated by rain-splashed soil. Remove these low-lying branches, and also any canes that
angle through the bush (crossovers). What remains is a narrower bush consisting of the most
upright canes.
STEP THREE:
Open the
center. If needed, remove
one to three large canes from
the center of the bush to
reduce crowding, improve air
circulation and phase out
older canes. Old canes to
target for removal are larger
and grayer in color, and are
more likely to be covered
with a fuzzy growth of foliose
lichens. The goal should be to
move through the field
rapidly by making large cuts
close to the ground.
STEP FOUR:
Thinning and heading back. As a blueberry cane ages, it branches repeatedly,
resulting in smaller and smaller diameter lateral twigs in successive years. If left unpruned, this
results in excessive numbers of unproductive, matchstick-sized shoots, each with a few tiny
berries. To avoid reaching this stage, thin canes by making cuts to selectively remove clumps of
twiggy, brushy-looking, matchstick-sized laterals. At this time also cut (head back) any long
whips or canes that are too tall.
About Flower buds
Yield reduction via flower bud removal always occurs when winter pruning is done properly.
This is often a sore subject with growers who are trying to maximize yields. Flower buds are
readily visible during winter pruning, and it is tempting to leave too many. This is a mistake!
Expect to remove at least a third of the flower buds during pruning. Why? Because overloading
the bush with fruit in one year will stress the plant and cause reduced yields in following years,
and will eventually require even more severe pruning to bring the bush back into production.
Conclusion
These basic hand-pruning steps can be used with any blueberry bush. Every cultivar has a
slightly different growth habit, and only experience will tell you how to manage each. Some
cultivars produce too many new shoots from the ground and require a lot of thinning, while
others are less prone to sprouting. Your goal should be to have a multi-trunked bush with
strong canes of all different ages emerging from the ground, so that as each older cane is
removed, a younger cane is already there to replace it.
Pruning Young Blueberry Plants
Young blueberry bushes are usually planted in late winter while fully dormant and leafless. In
North Carolina, this translates to February or early March. During the first year, flower buds are
removed by pruning, or by stripping off flowers by hand after the blooms emerge. In
subsequent years, flower buds must be thinned to prevent overcropping and to promote the
vegetative growth so vital to the establishment of a full-sized bush.
The diagrams below show growth of a single blueberry bush for the first three years, with
"before" and "after" pruning comparisons each February.
Prune at
time of
planting
Growth
st
during 1
year
February
nd
of 2 year
Growth
nd
during 2
year
February
rd
of 3 year

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