Grapevine plant named ‘Norton Blanc’

Latin name of genus and species:

Varietal denomination: ‘Norton Blanc’.

The present cultivar originated from a cross of ‘Norton’ (female) (not patented) and ‘Cabernet Sauvignon’ (male) (not patented) grapevines made in May 2005. Anthers were removed from ‘Norton’ grapevine's flowers, and pollen was collected from ‘Cabernet Sauvignon’ grapevine. The ‘Cabernet Sauvignon’ pollen was shed onto stigmas of ‘Norton’ grapevine flowers by gentle brushing. A paper bag was wrapped around pollinated ‘Norton’ flowers for one week and then removed to expose the formed berries.

In October 2005, 300 seeds were harvested from berries that developed from the aforementioned pollinated flowers. In March 2006, seedlings were germinated in a greenhouse, and in June 2006, 100 seedlings were planted in a vineyard at the Missouri State Fruit Experiment Station in Mountain Grove, Missouri.

From 2007-2011, viticultural traits of the 100 seedlings were evaluated. Seven new grape varieties, including ‘Norton Blanc’, were selected and planted at the Missouri State Fruit Experiment Station for further evaluation in June 2011.

From 2015 to 2020, 12 ‘Norton Blanc’ grapevines were evaluated at the Missouri State Fruit Experiment Station in Mountain Grove, Missouri, with 12 ‘Norton’ grapevines and 12 ‘Cabernet Sauvignon’ grapevines, the two parental cultivars, and six other selections, all grown in the same vineyard for comparison purposes. Since then, additional ‘Norton Blanc’ vines have been propagated, grown, and further evaluated for viticultural and enological traits.

In 2016, a first vintage white wine was made from ‘Norton Blanc’ grapes that were planted in 2011.

The present invention is a new and distinct variety of grapevine named ‘Norton Blanc’ produced from a cross of ‘Norton’ and ‘Cabernet Sauvignon’ grapevines. Although ‘Norton’ and ‘Cabernet Sauvignon’ are each red wine grape cultivars, ‘Norton Blanc’ is a white grape variety.

The fruit clusters of ‘Norton Blanc’ are small, but not extremely tight, and the berries are slightly larger than the berries of both ‘Norton’ and ‘Cabernet Sauvignon’ grapevines.

Bud break of ‘Norton Blanc’ is late compared to currently grown wine grape cultivars in Missouri, including ‘Cabernet Sauvignon’, and on average is four days later than bud break of ‘Norton’ grapevines. Observed bud break dates of existing ‘Norton Blanc’ grapevines in Missouri range from April 11th to May 4th. For the same ‘Norton Blanc’ grapevines, observed flowering occurred around Juneth, and observed veraison occurred around August 12th.

Harvest of existing ‘Norton Blanc’ grapevines in Missouri has been between September 20th and October 9th. This is slightly earlier than harvests for ‘Norton’ and ‘Cabernet Sauvignon’ in the same region, which is from September 27th to October 15, but later than harvests for most white grape cultivars. At harvest, pH values of ‘Norton Blanc’ are consistently around 3.35, while the pH of ‘Norton’ is around 3.39. Titratable acidity of ‘Norton Blanc’ ranges from 0.57 to 0.66 g/100 mL, which is lower than the average of 0.72 g/100 mL for ‘Norton’.

Sugar content of ‘Norton Blanc’ ranges from 20.3 Brix to 25.2 Brix, depending on the season. In most years, the sugar content of ‘Norton Blanc’ has been two degrees Brix lower than the sugar content of ‘Norton’, but higher than the sugar content of ‘Cabernet Sauvignon’;.

Over the years, yield per vine of ‘Norton Blanc’ has been very consistent, with the lowest yield being 11.2 lbs. per vine, the highest being 13.2 lbs. per vine, and the average being 12.35 lbs. per vine. ‘Norton’ had larger fluctuations in yield during these years, with an average of 14 lbs. per vine. ‘Norton Blanc’ is very cold-hardy in comparison with ‘Cabernet Sauvignon’.

When grown using a standard spray program in Missouri, all common grape diseases, including pre-harvest soft rot (, which was previously known as), were well controlled. ‘Norton Blanc’ is moderately resistant to downy mildew () and bunch rot () based on laboratory and vineyard evaluation. Further, ‘Norton Blanc’ survived late spring freezes in 2020 and in 2021. Additionally, ‘Norton Blanc’ is easily propagated from dormant wood cuttings, at about a 90% rooting percentage.

Wine produced from ‘Norton Blanc’ berries has an aroma of fresh spring grass or fresh-cut lime. The wine palate has a touch of green apricot, plum, or apple. The wine is light-bodied with a complex structure of balanced acidity. The wine is crisp, clear, clean, and sharp. Wine from ‘Norton Blanc’ is a new, unique style of wine as compared to traditional white wines.

‘Norton Blanc’ grapevine can be grown utilizing standard viticultural management practices, with no special techniques required. ‘Norton Blanc’ grows well for commercial production under the climate and soil conditions in the Midwest region of the United States.

The following descriptions of ‘Norton Blanc’ apply to grapevines planted in Mountain Grove, Missouri in 2015. When dimensions, sizes, colors, or other characteristics are provided herein, it is to be understood that such characteristics are approximations set forth as accurately as possible. Variations based on climatic conditions, fertilization, pruning, pest control, and other cultural practices and factors that impact the exact exhibition of certain specific characteristics are to be expected. Color codes used are those of The Royal Horticultural Society Colour Chart (1966. R.H.S. Colour Chart. London), and Galet's “A practical ampelography” (P. Galet: “A practical ampelography.” 1979, 248 pp. ISBN (Hardback): 978-0-8014-1240-0; CABI Record Number: 19790379291, Publisher: Cornell University Press, Ithaca. USA) was used to describe characteristics of ‘Norton Blanc’, except where general terms of ordinary dictionary meaning are used.