Article from Specialty Crop Industry
by Fumiomi Takeda
Growing Primocane-Fruiting Blackberries in Florida
 | | This
primocane-fruiting blackberry plant, Prime-Ark® Traveler, has some
primocanes bent on a training wire and three primocanes remaining
upright. Note that upright primocanes have not produced laterals. |
The introduction of primocane-fruiting (PF) blackberries by the
University of Arkansas is considered a major innovation in the
blackberry industry. Anytime a variety or new way of growing a crop can
extend the production and marketing season, the crop becomes more
important for growers and consumers.
In addition to extending
the season, this advance has expanded the commercial production of
blackberries in Central America, California and other areas with mild
winter conditions or in high-latitude regions with low winter
temperatures. In blackberry production, winter injury is a huge
concern. New cultivars and practices in PF blackberry production have
enabled growers and packers to ship high-quality fresh blackberries to
distant markets almost year-round in North America and to produce
blackberries in areas where floricane-fruiting (FF) production has not
been profitable due to winter injury. Some of these growing methods
should be evaluated for growing blackberries in Florida.
Blackberry
production in Florida is currently low. This has been attributed to
lack of inadequate winter chill hours for production in Central Florida
and areas further south. Lack of winter chill hours can cause poor and
erratic budbreak in deciduous fruit crops, including blackberries.
For
example, a blackberry farm near Haines City, Florida, planted recently
released FF blackberries Natchez and Ouachita developed by the
University of Arkansas in 5-gallon containers. These varieties produce
fruit on floricanes that go through a dormant or rest period in winter
and bloom and fruit the following year. The primocane development was
low, and fruit production on the floricanes was less than satisfactory.
The
low yield of FF blackberries grown in Central Florida is a result of
low budbreak (less than 20% compared to about 60 to 70% in U.S.
Department of Agriculture Plant Hardiness Zones 7 and 6) and low berry
numbers per shoot (about five per shoot compared to more than eight in
more northern states). In South Georgia, the same varieties have
produced 15 or more fruit clusters on 6-foot tall primocanes, with each
cluster producing eight or more large berries. The same FF varieties
grown near Mayo in North Florida are growing vigorously and are
producing ample amounts of tall primocanes with potential to produce
sufficient flowering shoots and good yields.
Primocane Manipulation
Recently
released PF blackberries produce fruit on current year canes and are
adaptable to different production systems designed to increase their
yields and produce fruit out-of-season. Their primocanes can be
manipulated to produce berries in early spring or in the fall. After
harvest is over, the canes can simply be cut off or mown down at ground
level. This growth characteristic in PF blackberries offers growers an
opportunity to produce blackberries even during winter months in areas
like Florida.
To increase yields in PF blackberries, primocanes
are typically tipped or topped after they reach about 3 feet in height
in late spring to encourage formation of one or two branch canes from
lateral buds just below the cut. If vigorously growing primocanes are
not tipped then they will continue to grow upward and produce fruit
only at their tips.
One study showed that in PF Prime-AArk®
Traveler, the early emerged primocanes were more productive than those
that emerged later in the season. Additional cane manipulation
techniques, such as bending them to force subsequent growth to occur
horizontally instead of growing vertically and removing leaves on the
primocanes, promoted flower production and produced more fruit compared
to those grown using the tipping method.
The primocanes that
emerged in April produced 64% more flower shoots than those that
emerged after May. The late primocanes that emerged in June were not as
productive as those that emerged in April, when they were bent and
leaves removed produced fruit until November when remaining berries
were damaged by frost.
PF blackberries can also produce fruit
with less than 100 chill hours. In Prime-Ark® Freedom blackberry,
research has shown that fruiting lateral numbers can be increased by
bending the developing primocanes and training the primocanes to
continue their extension growth horizontally. Also, these findings
indicated the alternative primocane management practices of bending to
orient primocanes to grow horizontally and removing the leaves
increased budbreak and flower shoot emergence. Flowers begin to emerge
at their tips four weeks after bud break along the entire length of
bent primocanes.
Remaining Challenges
Research
on PF blackberries has contributed to a better understanding of
primocane emergence time and orientation, flowering relationships and
how these factors improve cropping performance. Now the challenge is to
force low-chilled PF blackberries to produce sufficient numbers of
fruiting laterals and obtain high-quality fruit during winter at the
time when strawberries are being harvested in Florida.
Other
challenges for commercial blackberry production are to receive high
prices for fresh fruit and to have a system to produce blackberries
before or after summer months when Florida fruit is not competing with
blackberries coming from Mexico.
Selecting the right PF
blackberry variety and using a novel production method is another route
to consider for producing blackberries in Florida.
Fumiomi Takeda (fumi.takeda@usda.gov,
304-620-5694) is a research horticulturist with the U.S. Department of
Agriculture Agricultural Research Service at the Appalachian Fruit
Research Station in Kearneysville, WV.
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