Vitis aestivalis “Norton/Cynthiana” is a grape native to North America and utilized in the commercial wine industry. The purpose of this research was to determine the appropriate time of year and/or time after last freeze that will yield the most successful propagation rate for Vitis aestivalis. It was hypothesized that the highest rate of propagation would be in early summer. During a year-long study (2015-2016), forty cuttings were taken semi-monthly from a vineyard, treated with 0.1% IBA and placed in a plant growth room set to spring conditions. Daily temperatures were recorded every day as well. In a follow-up study, cuttings were taken weekly from early spring before vine budding until late fall (2017) and treated as previous. After six weeks, cuttings were evaluated for root production. In both studies, rooting success rates were the highest in the month of June at 10.0% - 27.5%, with rates less than 7.5% for all other sampling dates. It was determined that the best time to propagate Vitis aestivalis is in June, 10 - 12 weeks after the last temperature below 0 °C or eight to ten weeks after the first budding.
Vitis aestivalis “Norton/Cynthiana” is a species of grape native to North America and is grown as far north as southern Ontario, Canada, as far west as Oklahoma and as far south as Florida [
There has been speculation regarding the best procedure that will yield the greatest propagation rate. Attempts have been unsuccessful, to date, at substantially increasing propagation rates. For example, Enderton et al. [
The purpose of this study was to determine if sample date and timing of cutting harvest has a positive effect on Vitis aestivalis “Norton/Cynthiana” grape propagation efficiency.
Cuttings of grapevines were taken at the Rutherford County Agricultural Extension Services/MTSU vineyard (Latitude: 35˚51'15.39"N; Longitude: 86˚26'43.32"W). Semi-monthly sampling was accomplished from September 1, 2015 until August 16, 2016. The study was repeated during the active growth season in 2017, beginning April 4, 2017 and ending September 4, 2017. Upon arrival during each site visit, fifty grapevine cuttings were collected randomly in different locations throughout the vineyard. Each tissue selected for cutting came from the growing end of a vine. Each cutting was made below at least the fifth node from the tip of the vine. Cuttings were placed in a bucket of water, with the freshly-cut end submerged in the water to prevent them from drying out. Cuttings were then transported to the MTSU campus.
Cuttings were immediately returned to the MTSU campus. Sterilization procedures for the cuttings were not necessary. For each stem cutting, a fresh cut was made just below the fifth node, ensuring that the node itself would be submerged into the rooting medium. Each freshly cut end was wetted with water and dipped into rooting hormone (0.1% Indole-3-butyric acid), and the cutting was then placed into the rooting mixture. The rooting mixture was a 50:50 (V:V) mixture of Perlite: Vermiculite. This mixture helped to aerate the soil, as well as provide a higher level of water retention [
After six weeks in the growth room, the samples were removed from the Perlite: Vermiculite mixture and carefully inspected for rooting. If there was no rooting, the sample was discarded. If there was rooting, the cutting was recorded as such.
Local daily high and low temperatures according to the weather service, AccuWeather [
The physical appearance and general vine status of the grapevines was assessed and photographed during every site visit to the vineyard. This assessment was done to record initial budding in the spring, along with approximate dates for flowering and fruiting.
The percent rooting success rates for each sampling date were analyzed using a t-test (SigmaStat Version 3.1). The 2016 study and the 2017 study were analyzed separately.
Sample dates for the year-long study (2015-2016) were completed on a semi-monthly schedule. Sample dates for the second study (2017) were completed weekly in an attempt to better define the optimal sampling time. In both studies, some sample dates had to be adjusted for harsh weather conditions that prevented vineyard site visits.
Success rate was determined by dividing the number of cuttings that showed roots by forty, the total number of cuttings processed for each sample date. For the year-long study, the highest percent success rates were observed in the cuttings taken during the month of June 2016 (
In the second study (2017), the highest success rates were also observed in the month of June (
whereas the June 12, 2017 sampling yielded a 10% success rate. Samplings on June 17, 2017 and July 8, 2017 both showed a 7.5% success rate. The success rates for cuttings taken on June 12, 17 and July 8 were found to be statistically significant (t-test; p < 0.001). All other sampling dates yielded 0% - 2.5% success rates.
The daily high and low temperatures for the year-long study showed the last day with a temperature below 0˚C to be March 26, 2016 (
Assessments and photographs of the grapevine status at each sampling show that, for the year-long study, the date of first vine budding occurred on April 6, 2016 (
The Norton/Cynthiana grape has proven to be difficult to propagate via the traditional route of propagation, taking cuttings during dormancy. Results of this study demonstrate that traditional propagation cutting collection times (December to March in middle Tennessee) for this grape yield very low success rates (
August, all other sampling dates yielded propagation success rates of 5% and below. In both sampling years (2016 and 2017) the highest success rates for rooting occurred during the month of June. Rooting success rates approached 30% during June 2016.
While Enderton et al. [
High and low temperatures were recorded daily and the first budding date was observed because this grape is also grown in regions outside of middle Tennessee. These other geographical locations have different growing seasons, so the date of sampling itself in this study will not be meaningful. In the year-long study, the first significant success rate in June occurred ten weeks after the last day the temperature fell below freezing (March 26, 2016). In the 2017 study, the highest success rate for propagation occurred 12 weeks after the last day the temperature was below 0˚C (March 19, 2017). Therefore, based upon our studies, the best time to propagate this grape is 10 - 12 weeks after the last temperature below freezing. Commercial vineyards in states outside Tennessee will find this information more beneficial than an actual date when determining the optimal propagation time. The first significant propagation success rate in June also occurred eight to nine weeks after the first day of observed budding (April 6, 2016) in the year-long study and 10 weeks after first budding (April 4, 2017) in the second study. Vineyards in more tropical locations that do not experience a frost or freeze will find this reference to first budding to be beneficial in determining the optimal time to propagate.
High temperatures were evaluated over the period from February 23 to July 22, 2017 by calculating a trendline. Over this period, the slope of the trendline was 0.1142, indicating rising temperatures. As spring gives way to summer, rising daily high temperatures are expected and normal. In addition, daily high temperatures were plotted from June 5 to July 7, 2017, the period of time during which propagation rates were highest. The slope of this trendline was 0.0643. This indicates that the highest propagation efficiency occurred during the time period when daily high temperatures were essentially steady and unchanging.
Based on this study, advice to commercial vineyards in middle and/or west Tennessee is that the best time at which to take cuttings of the Vitis aestivalis “Norton/Cynthiana” grape is in the month of June. This can pose a problem due to the fact that fruit set occurs during the months of May and June. This is not a good time to take cuttings because it is not wise to cut vegetative tissue while trying to promote fruit growth. Therefore, our recommendation for commercial vineyards to avoid this problem is to set aside a host of vines which will solely be used in a given year as a propagation stock. It would be highly advantageous to remove all floral inflorescences from these vines before fertilization to promote as much vegetative growth as possible during the growing season, thus, having more vine tissues from which to take cuttings.
For regions outside of middle or west Tennessee that experience different weather patterns, collection of cuttings for propagation of this grape should occur 10 - 12 weeks after the last recorded temperature below freezing. For areas that don’t experience a frost or freeze, collection of propagation cuttings should occur 8 - 10 weeks after the first budding is observed.
This study was partially funded by Undergraduate Research Experience and Creative Activity (URECA) Grants to A.L.U. and N.J.
Uhls, A.L., Jolley, N., Johnston, T.V. and DuBois, J.D. (2018) The Effect of Sample Date and Timing of Cuttings for Maximum Propagation Efficiency of the Grape, Vitis aestivalis “Norton/Cynthiana”. Food and Nutrition Sciences, 9, 268-276. https://doi.org/10.4236/fns.2018.93021