High tunnels can be a part of a production system that
allows growers to produce berries year-round while improving fruit yields and
quality.
By David Kuack
High tunnels have different uses in different places,
said Marvin Pritts, professor and chair of the Horticulture Section of Cornell
University’s School of Integrative Plant Science in Ithaca, N.Y.
“In California, many growers use the tunnels for rain exclusion,”
Pritts said. “In other places, tunnels are used to help cut down on the wind
and to regulate temperatures. In the Northeast U.S. the tunnels work in
multiple levels. They offer protection from rain. They also offer some
temperature and wind control. Their only limitation in the Northeast is the
length of the seasons.”
Pritts said growers in the Northeast have been using high
tunnels for about 15 years.
“We have plenty of water, good soils and the population,”
he said. “It has been exciting for growers to see the response of the plants
grown in the high tunnels. Growers have been able to extend production by about
a month on either side of the growing season so that it is earlier or later.”
Pritts said growers of tomatoes, cucumbers and greens
have taken the most advantage of using the tunnels.
“Growers who produce tomatoes were the first ones who
really got into using the high tunnels in a major way,” he said. “That was
followed by cucumbers. These tunnels were used for summer vegetable production.
During the cooler season there are a lot of greens produced, including spinach,
arugula and some other greens that can almost be grown year-round in tunnels.
“Vegetable growers have been able to extend their
production season for a longer period than ever before. Also, growers have been
able to produce some crops, like blackberries and figs, that typically don’t
grow here in the Northeast. Tunnels allow growers to overwinter these crops.”
Supplying local
markets
Pritts said in the Northeast most of the crops are being
grown for local sales.
“The growers supply local grocery stores like Wegmans and
farmers markets,” he said. “Wegmans has its own farm where it is using high
tunnels to grow various crops for its own stores.”
Wegmans Organic Farm in Canadaigua, N.Y., uses high
tunnels to grow year-round at the 50-acre operation.
Pritts said he expects water restrictions in places like
California will cause more growers to look at incorporating high tunnels into
their production.
“At some point more of the production is going to have to
shift eastward,” he said. “Growers in the Northeast don’t have a long season,
but high tunnels offer some control. It makes sense to grow some of these crops
locally where the markets are, where there is enough water and it’s relatively
inexpensive to ship crops locally rather than shipping them across the country.”
Growing
raspberries year-round
Pritts said growers in the Northeast are using high
tunnels to harvest red raspberries earlier in the summer and to extend the
production into the fall. Because the use of tunnels for berry production is a
recent development, Pritts doesn’t really know which season the growers are
using the tunnels for more. He expects it’s both.
Most of the high tunnel research that Pritts has done has
been with primocane fall-bearing raspberries. These plants can be mowed down to
the ground in the spring and they grow up and flower and fruit in the fall.
Pritts said the canes can be pinched so that the plants flower and fruit later
into the fall.
“In October, raspberries aren’t available from
field-grown plants in the Northeast because the temperature is too cold,” he
said. “High tunnels allow raspberries to be picked in October when other
locally-grown berries aren’t available. Growers in southern states are already
done with their fall production. There also aren’t a lot of berries coming in
from other parts of the world at this time. For those countries in the southern
hemisphere, it would be too early to be harvesting berries. There is an
opportunity for local growers in the Northeast to take advantage of limited
market supplies. It’s a niche market.”
Pritts said growers also have the option of growing
summer raspberries producing fruit in late June and early July.
“Summer production requires more trellising because the
canes have to be maintained through the winter,” he said. “If a grower produces
summer raspberries, the high tunnels have to be kept up year-round. With fall
production, since the canes are cut back, the plastic covering on the tunnels
can be removed for the winter. Since the covering is going to be removed, the
tunnel structure doesn’t have to be as strong because snow loads aren’t an
issue.
Pritts said being able to take the plastic off of the
tunnels is a real advantage during the winter for the fall raspberries.
“Some of the salts in the soil can be leached out with
the normal snow and rain during the winter,” he said. “Then the plastic can be
put back on. If the raspberries are being grown in containers, then the growing
medium can be flushed to leach out excess salts.”
Pritts said if a grower is producing summer raspberries
or blackberries, the plants have to be brought through the winter in a tunnel.
“During a typical year, raspberries and blackberries make
it through the winter in a tunnel just fine, although these past two winters
were exceptions,” he said. “But the high tunnel has to be able to support the
snow loads in order to protect the plants. During heavy snow storms, especially
if the snow is wet, the snow needs to be removed from the high tunnel to
prevent it from collapsing. These structures don’t usually handle more than a
foot of snow.”
Pritts said it should be easier for growers to produce
fall-fruiting raspberries.
“Fall raspberry varieties can produce a summer crop, but
typically these varieties are grown solely as a fall crop,” he said. “If these
plants are grown as a fall crop and allowed to go through the winter, they will
produce a small summer crop. Most growers prefer to choose varieties
specifically for summer production.”
Pritts said a grower could use a combination of fall- and
summer-fruiting varieties along with outdoor field and high tunnel production
to produce a raspberry crop year-round.
Differences in
yield, quality
Pritts said one of the major reasons growers are
producing raspberries in high tunnels is because of the difference in fruit
quality.
One
of the major reasons growers are producing raspberries and blackberries (shown) in high tunnels is because of the difference in fruit quality, including having a longer shelf life. |
“Tunnels keep rain off of the fruit so that it doesn’t
get moldy as fast as field-grown berries,” he said. “The quality is like day
and night between raspberries grown in high tunnels and those grown in the
field. Tunnel raspberries definitely have a much longer shelf life.
“In regards to flavor, the raspberries grown in tunnels
are so high yielding that they are not as sweet as field-grown berries. Because
the yields are so high in tunnels, it is hard for the plants to provide sugar
to all that fruit. Even though the tunnel berries may be less sweet, the yields
are so much higher. If someone ate the tunnel raspberries and didn’t have the
field raspberries to compare them too, they would say the tunnel raspberries
were very good tasting.”
Improving plant
performance
Pritts said field-produced raspberries generally have a
10-year life span for the field they are being grown in.
“After a couple years for field-grown plants, there tends
to be a decline in fruit production,” he said. “In high tunnels we never
fertilize, but we amend the soil with compost before we plant. We don’t have to
fertilize because the vigor of the plants is already good. There hasn’t been any
decline in the yields of the high tunnel plants even after 10-12 years.”
Pritts said high tunnel plants aren’t exposed to the same
environmental stress plants encounter in the field.
“Soil pathogens survive when the soil is wet for long
periods of time,” he said. “In outdoor fields the soil is going to stay wet for
long periods. Many of the disease pathogens also like cooler temperatures. I
expect these pathogens gradually take the plants down in the field. In tunnels
there usually aren’t long periods of standing water as would occur in outdoor
fields.”
Another benefit of the high tunnels is wind exclusion.
“The stems on the raspberry canes are very thin and there
is a lot fruit at the top of the plants,” Pritts said. “When the wind starts to
blow, it whips the field-grown canes back and forth. This doesn’t happen in the
tunnels. Previous research has shown the wind can be very detrimental to
raspberry yields.”
Since the plants grown in tunnels aren’t exposed to the
rain, drip irrigation is used to water the plants.
“Irrigation in the tunnels is between the plant rows,”
Pritts said. “Outside when it rains the weed seeds germinate. In the tunnels
there’s not much weed pressure at all.
“Another advantage of the high tunnels is the fruit can
be harvested even when it’s raining, when it’s cold or when the wind is
blowing. People don’t want to harvest in inclement weather. The tunnels enable
a grower to schedule berry harvesting.”
Pritts said raspberry growers who use tunnels have to
closely monitor plants for two-spotted spider mite.
“The difference in the populations of two-spotted mite is
the biggest issue,” he said. “Outside, often times, growers don’t have to be
concerned with mites. The mites are in the field, but they are at very low
levels. They don’t like being wet so when it rains it depresses the
populations. In the high tunnel where it doesn’t rain, there is a dry
environment, which the mites thrive in.”
For more:
Marvin Pritts, Cornell University, School of Integrative Plant Science,
Horticulture Section, Ithaca, NY 14853; (607) 255-1778; mpp3@cornell.edu.
Other sources of information on the production of high
tunnel berries:
High Tunnel Raspberries and Blackberries,
http://fruit.cornell.edu/berry/production/pdfs/hightunnelsrasp2012.pdf.
Raspberry Variety Review,
http://www.fruit.cornell.edu/berry/production/pdfs/raspcultreview2012.pdf.
Low tunnel strawberries
Marvin Pritts, professor and chair of the Horticulture
Section of Cornell University’s School of Integrative Plant Science is also
doing a study on the production of strawberries in low tunnels. He is growing day
neutral strawberries, which flower and fruit nearly all summer into the fall, in
low tunnels.
“The strawberries are planted on a double row on a 16-inch
raised bed with white plastic,” he said. “Hoops, which are covered with plastic
film, go about 18 inches above the plants. The plastic is held down on the
hoops with bungee cords.”
Marvin
Pritts said it is about four times cheaper on a per area basis to grow strawberries in a low tunnel than in a high tunnel. |
Pritts said the plastic film helps to keep the
temperatures lower during the summer. The covered tunnels also retain some heat
during the fall.
“The sides of the tunnels remain up almost all the time,”
he said. “When it rains or it’s going to be cold or windy, the tunnel sides are
lowered. The strawberries produce high quality fruit which can be grown nearly
year-round.”
Pritts said it is about four times cheaper on a per area
basis to use a low tunnel than it is to use a high tunnel because a tall hoop
structure isn’t required.
“The plants only grow low to the ground so there’s no need
to construct a 15-foot tall structure,” he said. “Like in the high tunnels, the
plants in the low tunnels are watered and fertilized with drip irrigation. The
drip line runs down the middle of the bed between the two rows of plants.”
David Kuack is a freelance technical writer in Fort
Worth, Texas; dkuack@gmail.com.
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