By: Annie Klodd, University of Minnesota Extension Educator
Row orientation is one of the first decisions a grower makes when planting a new vineyard. But how much does this decision matter, and what should you consider when choosing row orientation?
For generations, many have touted north-south (N-S) row orientation as a best practice because it exposes the canopy to the most direct sunlight. But modern research suggests that, like many things, it is more complicated than this.
For some vineyards, north-south is the best choice. But a strict north-south stance could overlook other factors like field shape, variety, climate, convenience, and even aesthetics. The freedom to consider different row orientations can improve multiple aspects of vineyard management.
Benefits of North-South Orientation
Simply speaking, N-S row orientation directs more uniform solar radiation to the full canopy, compared to East-West (E-W) orientation. The east side of the canopy is exposed to direct light in the morning and the west side in the afternoon. A 2008 study (Grifoni et al) found that N-S rows received increased and more uniform solar radiation, and as a result, photosynthesis.
With E-W rows, the south side gets more direct sun than the north, possibly meaning that south-facing fruit ripens faster than north-facing fruit.
Why “It’s Complicated”
In theory, north-south row direction could enhance ripening and fruit quality by increasing sunlight exposure. However, current research paints a less clear picture.
Much of the research I have found was done in the southern hemisphere. Several of these studies took place in the same Shiraz vineyard in South Africa. Without much research in US climates, it is hard to draw too many conclusions about the region where I work, or the varieties we grow in the Midwest.
Secondly, many factors play into a grower’s decisions about row orientation beyond just sunlight interception, which I delve into later.
A 2015 study on mature vines in this South African vineyard found no significant difference in anthocyanins or grape mechanical composition between NS and EW rows. However, a later study from the same vineyard in a different year found that EW rows had lower soluble solid/titratable acidity ratios, lower anthocyanins, and lower phenolics. The other row orientations like N-S, NE-SW, and NW-SE ripened faster and produced better wine quality. Additionally, one study found that N-S rows had slightly higher yields than the other orientations.
While light exposure is of course important, too much direct sunlight on fruit can be just as harmful as over-shading. It can cause sunscald, which degrades the fruit and leads to rotting. For this reason, a grower with a south-facing VSP vineyard in a hot, sunny region may consider planting on NE-SW or E-W orientation to limit excess exposure. If N-S orientation is selected, the grower can alter canopy management practices like leaf removal to control overexposure.
Other factors to weigh against row orientation
Growers should weigh various other decisions against row orientation when planting a vineyard. Field shape, variety, trellis system, weather, and climate all influence the bottom line and could either outweigh or exaggerate the impact of row orientation.
Like row orientation, trellis systems also affect sunlight exposure and ripening. In theory, planting N-S rows to Vertical Shoot Positioning (VSP) could compound the effect of row orientation by further increasing sun exposure. Planting on Single High Wire (SHW) might reduce the sun exposure for vines in N-S rows, protecting them from sunscald in hot, sunny areas.
Consider the field shape, row length and number of rows when deciding row orientation. If a field is long from east to west and narrow from north to south, the east-west row orientation would mean longer and fewer rows, less turning around, and fewer end posts to install.
Varieties: In short-season regions like the upper Midwest and Northeast, varieties with longer ripening times should benefit more from NS orientation than shorter-season varieties. For example, Frontenac is a popular cold hardy hybrid that needs a long ripening period to lower acidity. I would hypothesize that NS orientation might benefit Frontenac by helping it ripen faster, avoiding the first frost. Shorter season hybrids like Itasca, Marquette, and LaCrescent that ripen well before the first frost may benefit less from NS row orientation. More research on the cold hardy hybrids is needed to support this hypothesis.
Consider your climate as well. In hot, dry, sunny regions, grapes on the western side of N-S rows, and the southern side of E-W rows, are at a higher risk of sunscald. Sunscald risk would be further increased by using VSP trellising and late leaf removal. The sun hits the west side of the N-S canopy in the afternoon when temperatures are highest and sunlight is most intense. For this reason, growers may rotate the rows by 45 degrees, opting for a SW-NE orientation. As some regions become hotter and drier, practices to mitigate overexposure will be important (source).
Lastly, an individual winery may have aesthetic reasons to choose one orientation over another, like creating the perfect wedding photo spot or a dramatic view down a hill.
Row orientation is just one of the many factors determining the overall success of a vineyard. Hopefully this information helps growers plug it into the big picture when making key vineyard planting decisions.