Site selection for grapes

Ontario has four wine regions: the Niagara Peninsula, Lake Erie Northshore, Prince Edward County, and Pelee Island. The Niagara Peninsula is located South of Lake Ontario and West of the Niagara River, and has a climate further moderated by the Niagara Escarpment. Lake Erie Northshore is located North of Lake Erie and accumulates the highest heat units in Ontario each summer. Prince Edward County is the coolest viticultural area in Ontario, but has the benefit of moderated temperature from its proximity to Lake Ontario. Pelee Island has only one winery located on it. Though differences exist between the viticultural areas of Ontario, a general understanding of both climate and soil are needed to successfully plan for planting a vineyard in an optimal site within each region (GGO, 2010).

Climate and weather Concerns:

In Ontario, climate is the most important consideration when selecting a viticultural site. In these cool climate areas, not only is winter hardiness a concern, but also the ability of the grapes to ripen properly each growing season.

For grapes to ripen, a minimum of 155 frost free days is recommended for early-ripening grapes, while a minimum of 180 frost free days is recommended for late-ripening varieties. Another indicator of grape ripening potential is heat summation expressed as the number of growing degree days (GDD). GDD are calculated from the average minimum and maximum temperatures each day between the months of April to October, then subtracting 50°F from each value and summing up these values. A minimum of 2500 to 3500 GDD is required to ripen most vinifera varieties, while as few as 1800 to 2500 GDD can be enough to ripen some Hybrid varieties and early-ripening vinifera varieties (Wolf, 2008).

Extreme cold winter temperatures, spring frost, and autumn frost are also a concern for viticulture in Ontario. Though the effect of extreme cold temperatures differs across and within grapevine varieties, winter temperatures that fall below -22°C is often seen as a risk; some varieties are susceptible at temperatures as high as 0°C during dormancy. Healthy grapevines exhibit greater winter hardiness than vines that have been stressed, for example by drought stress or by early autumn frost. Wind machines have been shown to help protect grape vines from winter injury. Cool autumn temperatures are of concern in grapevines, because the accumulation of carbohydrates in the roots, trunks, and other perennial organs prematurely ceases, decreasing the winter hardiness of the vines. Spring frost is also a concern in Ontario, as vines that have undergone bud-break have a decreased tolerance to temperatures that drop below freezing, and a loss or reduction in crop can occur for that growing season. Sites located close to large bodies of water can help to moderate cold temperatures to decrease risk of winter injury and spring frost damage (Wolf, 2008). Cool Climate Oenology and Viticulture Institute (CCOVI) provides updates to growers on bud hardiness and winter injury.

Dry weather is has not often been a primary concern for vineyards in Ontario, due to adequate rainfall in most of the province. . However, several years of dry weather in Ontario have resulted in problems including low yields, poor shoot growth (Zn and B deficiencies), pest problems (erineum mite and European spider mite) and enological issues (low sugar; low pH and K; atypical aging). As a result many growers and wineries are examining the need and feasibility of irrigation for grapes. It is wise to consider water availability when selecting a vineyard site. Excess precipitation is another problem, and it is not recommended to plant varieties that are prone to rot and splitting in areas with high late summer and fall precipitation. (Wolf, 2008)

Soil and land characteristics:

Soil moisture, soil composition, and water drainage are highly important in vineyards; however, most of these factors can be altered to a certain degree. The best soil textures for growing grapes are loam, sandy loam, and sandy clay loam; while soil with high silt or clay content are less desirable due to inadequate drainage. Growing grapes on fertile soils can result in excessive vigour resulting in poor quality and yields. Training systems can be used to help manage vine vigour. Many vineyards in Ontario require drainage tiles, due to the high clay content in the soil. Sloped land, preferably between a 5% and 15% slope are also ideal to further enhance water drainage. Sloped land is also important for climate control, as it can assist with adequate air drainage. South facing slopes most optimally enhance heat units received by the grapevines. (Wolf, 2008)

Air drainage is also important to avoid cold pockets during winter freezes, and frost pockets during bloom or at harvest. Windbreaks and neighbouring forests can create problems with cold, although these features may offer some benefits with wind abatement. Recent losses due to spring frosts has encouraged some Ontario growers to invest in wind machines, so it may be prudent to consider where machines could be located to be effective if needed. (OMAFRA, 2012)

Take a hard look at this short list of potential problems, and decide what can be done to correct things before proceeding with a new vineyard.


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