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Blueberry Culture
Blueberries
are native to the eastern United States. Pacific Northwest
varieties are hybrids of these natives. They are self
fertile, but plant at least two different cultivars near one
another to ensure optimum fruit set and size. When honey
bees visit the blossoms in their search for nectar, the
plants yield the most fruit. An early, midseason, and late
variety can be planted to extend the harvest season.
Planting:
Heavily compacted soils, or those low in organic matter,
greatly benefit from the addition of compost, rotted manure
or sawdust. Amendments improve the soil texture and
increase the water holding capacity. Blueberries do not
like to sit in heavy clay that does not drain well during
the winter, but they do like their moisture during the
growing season. Blueberry plant roots are relatively fine
and shallow (14 to 18 inches), and prefer an open porous
soil. Add 4 to 6 inches of compost initially, and 1 inch
each year to maintain depth.
Blueberries do not demand as much soil dept for rooting as
cane berries and strawberries, but try to select a site with
at least 18 inches of free-draining soil. Install drain
tile in areas that may flood during winter months.
Grow blueberries in full sun for optimum fruit production
and quality. They will perform adequately, however, in a
location that receives partial sun. In areas of high summer
temperatures, partial shade prevents soil moisture loss and
keeps fruit from shriveling. Eliminate all weed growth
where you’re going to plant.
Fertilization:
Delay fertilizing young, newly transplanted blueberries with
chemical fertilizer to avoid burning root systems. Never
put fertilizer in the planting hole. Always use organic
fertilizer; blueberries love it! Fertilizing blueberries
during the first 3 to 4 years encourages development of a
number of well-spaced, stocky canes with many branches. Use
a balanced fertilizer, such as fertilizer for Rhododendrons,
Azaleas, and Evergreens, at leaf bud break and again during
late spring; then follow up with another application in June
if the leaf color is off. (If you’ve mulched with sawdust)
Watering:
Lack of supplemental watering from June to August severely
limits successful production of blueberries in the Pacific
Northwest. Shallow-rooted plants require close attention to
maintain a uniformly moist environment around their base.
They require 1 inch or possibly 2 inches of water each week,
in the absence of any rainfall. Be sure the entire root
zone is wet after irrigation. Drought symptoms include red
foliage, weak, thin shoots, and reduced fruit set. Maintain
a 2 – 5 inch mulch layer to preserve soil moisture. Keep
watering the plants through August to ensure good fruit bud
development for the following season’s crop.
Pruning:
Pruning is essential for both the production of high-quality
fruit and the maintenance of a healthy plant. During the
3-4 years, pruning consists of removing weak shoots, canes
that are not erect, and dead canes. Retain the longer,
heavier fruiting canes. During the first 2 years, fruit
buds should also be removed. (our blueberries in 2 gal. and
above are 2 years and older) Fruit buds are found at the
terminal 6-10 inches up the canes, and are fatter and
rounder than leaf buds, which are found farther down the
cane. When plants become 5-6 years old, begin to remove
some of the canes at ground level, retaining 1 to 3 year old
wood for best fruit production. On older bushes, production
often declines as canes age and produce fewer fruit buds.
To renovate the planting, remove canes with a basal diameter
of more than 1 inch at the ground line. This practice does
not affect subsequent yield but ensures strong return bloom
and larger fruit size. Prune during the fall, as opposed to
the winter and spring, tends to delay spring bloom and
reduces possible spring frost damage.
Diseases:
Mummy berry is the most serious fungal disease of
blueberries. It leaves affected fruit hard, and inedible.
During a prolonged, wet spring, the incidence of this
disease can be quite high. In late March mummified fruit on
the ground from the previous summer sprout minute, brown,
mushroom-like cups that release fungal spores. The spores
infect new flower clusters and leave them blackened and
withered. Spores produced on these blighted tissues infect
opening flower blossoms, which subsequently produce infected
fruit. Infected berries appear normal until the onset of
ripening. They then turn a tan to salmon color. Control
Mummy berry by raking the soil or mulch layer beneath the
plants as leaf buds swell in early March. Raking destroys
spore cups. Pick off and remove infected berries from the
patch before harvest. Pick up and throw away infected
berries that fall to the ground. A fungicide can be sprayed
on developing blossoms to protect them from the fungal
spores. An integrated program of spring raking, blighted
shoot removal, mummy removal, and use of protective fungal
sprays will contribute significantly to Mummy berry
control. If mummy berry has been a problem for you in the
past, a fungicide spray program may be necessary. An
effective fungicide spray program involves applying
fungicides regularly (every 7-10 days) throughout the period
when bushes are susceptible – from bud break (or when
mumyberry cups are first observed) through the end of
bloom, If frost occurs between sprays, re-apply fungicides
immediately after the frost event has been shown to improve
disease control. Copper is an effective fungicide. Copper
applied to the bushes at bud swell can reduce shoot
infection.
Botrytis blossom blight can also be a problem during a
prolonged, wet spring. Gray fungal spores distinguish
Botrytis infection from frost injury. If rains occur before
harvest, Botrytis fruit rot can infect maturing berries.
Reduce the incidence of gray mold by keeping the plants well
pruned. This improves air circulation. Do not let the
berries become over ripe on the bushes. |
