In the Vineyard


An equatorial mountainous site in Colombia. There is potential for grapes but not without


challenges. GARY STRACHAN


Equatorial viticulture far from easy


In a region with uniformtemperature year-round, variety selection tominimize cool temperature dependencemay be critical to ripening the crop.


By Gary Strachan A


generation ago, many viticultural textbooks included a diagram with two bands across the map of the earth between the 68 and 50 degrees (Fahrenheit) isotherms. These bands exclude the northern United States, all of Canada, Central America, northern South America, most of Africa, all of India, and the northern half of Australia. Today the lines are more blurred because of climate change and because of advances in viticultural practices.


Grapes are one of the most versatile genus. Native species are distributed over much of Eurasia and from the Southern United States to Manitoba. Within the dozen or so North American species there are local variations, as there are with the more familiar varieties of Vitis vinifera, the grape species of Eurasia that dominates commercial viticulture and winemaking. (For example, the difference between Riesling and Chardonnay.) These are variations within a single species that reflect each grape’s origins. Throughout all growing regions, grapes have a few fundamental requirements: a supportive soil with mineral nutrients, adequate sunlight, adequate season length, and protection from infestations and infections. Native species from a particular region have often survived because they have adapted to adverse conditions that would be lethal to varieties native to another region.


For example, in B.C. recent experience has shown Merlot to be more tolerant of hot summers than Pinot noir. Early attempts to grow European grapes in North America failed because they had no resistance to endogenous North American infections to which they had never been exposed.


What is different about equatorial climates that would 18 British Columbia FRUIT GROWER • Winter 2016-17


exclude viticulture? The first factor is day length. At the equator, the night and day are each 12 hours, year-round. Some grapes are dependent on diminishing photoperiod to signal the end of vegetative growth, the initiation of cane maturation, and fruit ripening. In France, this transition is referred to as aoûtment, the maturation of vines that initiates in August when the days start to shorten. This could be a handicap at the equator for vines that depend on photoperiod to ripen fruit.


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