Three vine management systems were evaluated on `Chardonnay' grapevines under Michigan growing conditions for five growing seasons to determine their influence on yield, fruit quality, cluster compactness, and the incidence and severity of fruit rot. These systems used mid-wire cordon (MWC) vine training, Umbrella Kniffin (UK) vine training, and a combination of those (UK/MWC). Over four growing seasons the UK and UK/MWC treatments had higher fruit soluble solids and higher yields than the MWC treatment. These higher yields were attributed to higher yields per node and the ability to retain more live nodes per vine than was possible with the MWC treatment. The UK and UK/MWC treatments also had less fruit rot than the MWC treatment in some years, which was related to reduced compactness of clusters. The UK and UK/MWC treatments produced greater numbers of mature canes per vine than the MWC treatment, and the locations of the canes allowed full cropping the season following an extremely cold winter.

Producing the cold-tender wine grape Merlot is a major challenge in the cool-climate viticultural region of southwestern Michigan. Merlot grapes produced in this region provide a strong market opportunity; therefore, several strategies for preserving the fruiting potential of vines through the winter were evaluated over 5 years. Vines were managed with frequent trunk renewal so that they were pliable and capable of being laid near the ground. One treatment was (A) a control. Three treatments involved pruning vines in the late fall to two to four canes, which were then (B) laid on the ground without any cover, (C) attached to a wire near the ground and covered with straw, or (D) attached to a wire near the ground and covered with 20 cm of soil. The fifth treatment (E) involved arching unpruned vines to place canes near the ground but without any covering. Pruning was completed in spring, and vines were tied using fan training. Vines were adjusted to a maximum of 40 live nodes per vine. Winter minimum temperatures averaged 1, 8 and 16 °C warmer than the air temperature at 1.5 m above ground when measured at 0.3 m above ground (B and E), under the straw mulch (C), and under the soil (D), respectively. Very low ambient air temperatures of –27 and –28 °C were experienced in two of the winter periods. C, D, and E consistently provided greater node survival through the winter than control vines. B was inconsistent in performance. The lowest annual yields for A through E for the 5-year period were 3.1, 0.7, 8.3, 6.7, and 9.0 tons per hectare, respectively. These data indicate that treatments C, D, and E were capable of reliable annual production of Merlot grapes even in years with episodes of low winter temperatures. Projects are under way to develop commercial capability for the vine burial and mulching techniques used in this study.

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