Bloom is one of the common times for grapevine tissue nutrient sampling. This information is the most useful to look at if you have multiple years of data on the same vines (or want to start that collection) or noticed some foliar nutrition symptoms in the vines previously (as the symptoms are less likely to show up at this point in the season). Young vines can show nutritional deficiency or toxicity symptoms earlier than more mature vines, but you’re more likely to see the symptoms at or after veraison.
Q: Should I collect leaf blades or petioles?
A: The leaf “blade” is generally what we think of as the ‘leaf’, while the “petiole” is the stem connecting the blade to the shoots. There is currently quite the debate going on which is better, as each has its pros and cons. While I sometimes change my preferred tissue (I think I’m currently on team leaf blade), it’s generally better to remain consistent over the years.
Q: Where on the vine should I collect the tissue?
A: At bloom either the leaf blade or petioles that are across from your flowering. If you are collecting petioles, ~80-100 are needed in the sample. While you can get away with fewer leaf blades, that can also mean a less representative sample – so at least 50 should be collected. Each of the samples should be grouped by the grape variety, rootstock combination, vine age, topography (vines on a hill versus on flat ground).
Q: When should I collect samples?
A: Nutrient levels can fluctuate quite a bit over bloom. On top of that, Georgia can often see bloom happening over a fairly long period of time that can be affected by winter temperatures, frost events, herbivory, etc. Again, most important for timing is trying to be consistent between years. Often, people aim for 50% bloom, when about half of the future berries have lost their caps.
Q: Can I just take soil samples?
A: Taking a grapevine tissue sample is more representative of the grapevine nutrition over soil tests – think of getting a blood test to test your own health rather than just looking at the nutrition facts on your morning box of cereal! I prefer to use soil tests mostly to look at pH (which is also very important for allowing vines to absorb nutrients.
Q: Where can I send the samples?
A: There are many labs that can process these samples, including the University of Georgia Agricultural and Environmental Services Lab (http://aesl.ces.uga.edu/).
If you have additional questions, see the resources below and feel free to reach out to me or to your county Extension Agent! — By Sarah Lowder, Assistant Professor, Extension Viticulturist, UGA Dept. of Horticulture
- VIDEO: Petiole sampling and analysis – Ohio State Extension – https://www.youtube.com/watch?v=ip2-nZeHJuk&ab_channel=OSUExtensionProfessionals
- Leaf blade versus petiole nutrient tests at predictors of nitrogen, phosphorus, and potassium status of ‘Pinot Noir’ grapveines. Schreiner, R.P. and Scagel, C. F. 2017 https://journals.ashs.org/hortsci/view/journals/hortsci/52/1/article-p174.xml
- Monitoring grapevine nutrition – Schreiner, R. P., and P. Skinkis. 2019. eXtension USDA-NIFA. https://grapes.extension.org/monitoring-grapevine-nutrition/
- Nutrient Management in 2008 Wine Grape Production Guide for Eastern North America – Batese, T., Wolf, T.,K. https://ecommons.cornell.edu/handle/1813/67189
- Fundamentals of grapevine tissue sampling for nutrient analysis – Hickey, C., Breeden, S., MacAllister, C., Lessl, J., Schreiner, R.P. https://extension.psu.edu/the-fundamentals-of-grapevine-tissue-sampling-for-nutrient-analysis
- June 24th – GWP New Grape Grower Symposium! Carrollton, GA – Registration now open early bird $65 until June 1st – https://www.georgiawineproducers.org/event-5284992
- July 20th – GiESCO Professional Day – Applied Viticulture Presentations VIRTUAL $75 or in- person ($150) in Ithaca, NY. https://cals.cornell.edu/giesco