Nov 6, 2008

English Growers Love Their High Tunnels

Growing sweet cherries in England is a challenge, to say the least, with the constant moisture and windy conditions. Organic sweet cherry plantings in that climate face even more challenges because of the lack of good organic fungicides for brown rot control.

To take weather out of the equation, Haygrove’s sweet cherry plantings are in tunnel structures 28 feet wide and 15 feet high. The sweet cherries are on Gisela 5 rootstock with three rows per bay and a tractor drive-row on the right side of the tunnel. The trees are planted in a triple-row formation -– 6 feet apart in the rows and 6 feet between rows.

All trees are staked, and they use nails off each stake to tie strings to branches when training the trees. Drip irrigation goes down each row and black plastic is used for weed control. When the cherries are ripe, they put bird netting on the ends of the tunnels to prevent damage.

Some of the major issues for the organic plantings are increased mite and aphid problems. Brown rot is much less of a problem under the tunnels, which works well with organic production because there is no organically approved product to control the disease.

The plastic is put on over the tunnels right before bloom and taken off in August so the trees will get enough light to produce fruit buds for the next year. If it gets too hot in the structures, the plastic must be rolled up to vent out the hot air. The plastic over the trees stops the rain from cracking the cherries, and they have seen marketable yields increase 25-30 percent.

Pollination is achieved using three triple bumblebee hives per 5 acres, and they also set out honey bee hives around the outside of the orchard. They have the sides up and ends open so the bees can get in unabated and do their job. A few of the English growers said the bees sometimes go up and hit the top of the tunnel until they get their bearings. There is some mortality of bees but not enough to worry about. Since it is warmer in the tunnels and doesn’t rain under them, some of the growers thought they actually get better bee activity.

VOEN System

A relatively new way to grow sweet cherries involves more of a roof structure than a tunnel, which Haygrove calls the VOEN system. The name VOEN is a combination of the names of two German growers who developed it, and it is basically a large structure of steel pipes and wires built around a block of cherries. They use a special covering that has hail netting on the bottom layer and a top layer of landscape-like cloth in strips that work like the gills on a fish to vent out the warm air. The good thing about this design is that you never have to raise up the poly to vent it, as with a traditional Haygrove high tunnel. That saves labor costs, but it is more expensive to put up. The special cover lasts eight to 10 years, compared to the poly that lasts three to four years.

The temperatures during the growing season under the VOEN are cooler, so it minimizes earliness. One of Haygrove’s sweet cherry plantings is 800 feet above sea level and has a cooler climate, so the sweet cherries are usually two weeks later than at its other farms. They normally finish picking by mid-August and are able to hit the late market. Bird netting is always put on the ends of the structure to stop the winged vermin from entering.

The trees in Haygrove’s VOEN system were all on Gisela 5 or 6 rootstock and planted in single rows 9 feet apart, with the trees 3 feet apart in the rows. They use a trellis system to support the trees, with wooden posts along the row with wires at 4 and 10 feet high. Each tree has a bamboo stick attached, and wires with rubber clips hold it all together. The bamboo is not buried and is about 1 foot above the ground.

Another high tunnel sweet cherry operation is Lower Hope Farm, where farm manager Andy Hunt runs the show. The operation has 60 acres of sweet cherries under high tunnels. To save money, they grow the trees outside for the first three seasons and then cover them with the tunnels. The cherries were all planted on Gisela 5 and were on a different planting system than the three-row system with a tractor drive on the right that Haygrove uses. Hunt said he has gone to a row on each side of the tunnel, with 10.5 feet between the rows for a tractor driveway. He said putting three rows of trees so close together makes it too hard to manage, but the system does give up some yield in the early years.