December 1, 2009, Corvalis, OR — Fruit growers' profits have traditionally been
limited by the seasons, particularly in colder climates where growing seasons
can be short.
December 1, 2009, Corvalis, OR — Fruit growers' profits have traditionally been
limited by the seasons, particularly in colder climates where growing seasons
can be short. Thanks to researchers and fruit breeders, newly developed
varieties are being introduced that offer growers the ability to produce fruit
during the offseason—resulting in economic bonuses for both producers and
consumers. Fresh examples are the new varieties of blackberry called
"primocane-fruiting", which bear fruit on current-season canes, or
primocanes. Primocanes can offer distinct advantages over traditional
floricane-fruiting varieties, which must be overwintered and produce fruit the
second year. These unique blackberries could greatly impact production efforts
by extending the harvest into the fall and winter months in milder climates.
Researchers have established that harvesting of
primocane-fruiting raspberry can easily be delayed in production systems that
include techniques such as summer pruning, tipping, and tunnel protection. To
determine the effect of management techniques on yield and fruiting season of
blackberry, Ellen Thompson and Bernadine C. Strik from the Department of
Horticulture at Oregon State University recently experimented with a
primocane-fruiting variety called 'Prime-Jan'®. The team evaluated the effect
of fruiting season on the chemistry of fruit ripened on plants grown in tunnel
and open-field production systems. The results were published in a recent
edition of the journal HortScience.
Plantings were established at the OSU–North Willamette
Research and Extension Center (Aurora, Oregon) in May 2005; half under a high
tunnel and the remainder planted in an adjacent open field. In 2006-07
primocanes were subjected to four treatments to promote branching and/or delay
harvest: all primocanes were cut to the ground when averaging 0.25 m tall, then
later emerging canes soft-tipped when reaching 0.5 m tall; all primocanes
within the plot were cut to the ground when averaging 0.5 m tall, then later
emerging canes soft-tipped when reaching 0.5 m; primocanes double-tipped (all
primocanes within the plot were soft-tipped when averaging 0.5 m tall with
subsequent lateral branches then soft-tipped when reaching 0.5 m long); and
primocanes were soft-tipped when averaging 0.5 m tall.
Fruit harvest began in mid-September in the open field and
tunnel, but lasted up to 3 weeks longer in the tunnel. Primocanes that were
double-tipped had nearly twice the flowers and fruit than canes that were
soft-tipped only once. In the tunnel, cumulative yield of double-tipped
primocanes averaged a 267% (2006) and 159% (2007) increase compared with the
control. Strik noted that "on average, cumulative yield for all treatments
was less in the open field than in the tunnel". The report noted that
harvest date affected fruit pH in 2006, but not in 2007. In 2006, fruit pH was
highest in the early season. All other differences in fruit chemistry were not
significant.
Another significant finding: primocanes that were
double-tipped produced an average of 33% heavier fruit than other treatments.
The research showed that the pruning and tipping systems used in the experiment
resulted in increased yield and offered options for extending growing seasons,
giving blackberry growers valuable new information that could lead to increased
profits.
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