Cane and Bud Hardiness of Own-Rooted White Riesling and Scions of White Riesling and Chardonnay Grafted to Selected Rootstocks

¹ Department of Horticulture, Michigan State University, East Lansing, MI 48824.

Controlled freezing tests were used to evaluate the cold hardiness of White Riesling own-rooted and grafted to the clonal rootstocks Kober 5BB (5BB), Couderc 3309 (C-3309), and Selection Oppenheim No. 4 (SO4) and Chardonnay grafted to 5BB and SO4. T₅₀ values were compared for each sampling date. Shootless node data and components of yield data were also collected. Of the White Riesling treatments, grafted White Riesling had significantly hardier canes in one of three years studied. White Riesling grafted to C-3309 had significantly fewer shootless nodes in one of four years studied. Bud hardiness was variable but showed White Riesling grafted to 5BB to have hardier buds in most cases. Because bud mortality can be compensated for to some extent, we feel that, of the rootstocks tested, C-3309 is most desirable in relation to winter survival since it encourages hardier canes and can help to reduce the numbers of shootless nodes in some years.

Key words: White Riesling, Chardonnay, cold hardiness, rootstocks, controlled freezing

Submitted on February 5, 1987