Reaching for the Wind: Capturing the wind to create targeted climate change in the Okanagan (2007)
Harness the Power of the Wind
By Deborah Greaves
Orchard & Vine Magazine, Summer 2007
Climate change isn’t always a negative. When induced on an acre-by-acre basis by determined human beings, climate change on a micro level can save entire crops from damage, even complete destruction. One of the effective ways to achieve targeted, localized “climate change” is to use a wind machine.
One of the fastest ways capricious Mother Nature can take a bite out of a season’s fruit crop and its profits is with an unexpected freeze-drying session. Cherries, a petite, rotund and soft-skinned fruit, are particularly susceptible. Grapes too are affected. Though grapes can often withstand a frost, the long-term health of the vines – as well as the flavour and quality of the fruit – can be compromised when the temperature drops at the wrong time.
The Okanagan Valley and other regions are known for late spring frosts so, to protect their crops, growers plan and work constantly to keep one jump ahead. When installed in the correct location, wind machines can make a crucial difference.
“If the temperature suddenly drops to 17 degrees Fahrenheit just after the first swelling of fruit,” says wind machine retailer Don Cachola, “it can mean a 10 per cent kill of that crop. If the temperature drops to 5 degrees F, up to 90 per cent of the crop can be killed.”
Cachola speaks in degrees of Fahrenheit rather than Celsius because most of the wind machines he sells and services through Okanagan Wind Machines are built in the U.S., where tens of thousands of the wind units are in regular use, particularly in California.
Some growers say climate has always been unpredictable, while others maintain the weather is becoming more erratic. Despite the current over-all warming trend, temperature drops such as the minus 20’s of November 2006 are expected to make the growing of tree fruits and grapes a delicate gamble for years to come.
“Grapes are a little more resistant to spring frost,” Cachola says, “but in fall, grape vine leaves should be retained for as long as possible. This helps sugar levels in the grapes and changes the flavour, which makes them more valuable.”
A freeze can cause grape vines to loose leaves too early, agrees grower Rod King of King Family Farms. “If you lose leaves, you lose photosynthesis and all ripening of the grapes stops,” says King. “When you keep the leaves, the ripening of the fruit is assisted and so is the storage of carbohydrates in the canes to nourish the plant through the winter. Carbohydrates act as a sort of antifreeze.”
In spring, when fruit is at a crucial stage, just a few degrees can have a drastic effect on profits. Cachola says cherry crops at the first white stage suffer a four per cent loss at a temperature of 27 degrees F, but a drastic loss of 90 per cent at a temperature of 24 F.
“cold air is heavier, and sinks to the lowest levels of an orchard, where it can cause the most damage to fruit when there’s a frost,” says Glen Luca of the B.C. Fruit Growers Association. “If the fruit has been pollinated when the frost hits, the fruit will be marked and unmarketable.”
This challenge, says Lucas, is the reason most orchards and vineyards are situated on hillsides. The slope helps to encourage cold air to flow down and away from the fruit.
What worries growers are those times that natural flow isn’t enough and the cold air settles in. “On a clear night with no cloud cover and no wind,” Don Cachola says, “the cold air lied close to the land and keeps the crop chilled. A standard wind machine can move warm air over 10 acres of land.”
For some Okanagan growers, that pulled-down, naturally-warmed air can provide a layer of insulation over their profits, as well as their fields.
It Can Pay to Intervene with Nature
Though the number of wind machine in use in the Okanagan Valley is currently small, grower Rod King of King Family Farms knows from experience that it can pay to intervene in Mother Nature’s frost plan.
King Family Farms just installed its third wind machine. At $25,000 retail for a new machine and at least $16,000 for a used one, it’s a hefty investment.
“Before installing wind machines,” says King, “we used water to reduce temperatures in our vineyard, because water releases heat as it freezes. However, you’re restricted on water use, so you can’t protect an entire vineyard. Also, the fruit absorbs some of the water, which dilutes the acids and flavour.”
Water, King says, can cause other problems. In Pinot Noir and Pinot Gris grapes, with their small, tight clusters of fruit, moisture in the cluster can create a climate for disease.
King says this has been a good year, but recalls just four or five years ago a frost on May 23.
"Last spring and fall in particular,” says King, “we had very warm days, as high as 20 degrees Celsius, with cold nights as low as minus five degrees Celsius. The wind machines were useful.”
What does a wind machine do to assist growers? Perhaps not what you imagine.
Wind machines move wind, but not often by blowing it. “The gear box of the wind machine is set at a six-degree angle,” supplier Don Cachola says, “so it isn’t blowing the wind, it’s actually sucking warm air down, from as high as 75 feet in the air above the crop.” The warm air then bathes the fruit and plants, protecting them from the frost effects.
There are other uses for wind machines when danger of frost has passed: The tall, imposing-looking units can aid in drying cherries and other fruit after rain or irrigation, cooling off cattle, and even controlling fumes from landfills.