Since the first seasonal opportunity for vine tissue sampling comes at bloom, this message may be timely for vineyards that are northerly and/or at higher altitudes, but somewhat late for those located more southerly and/or at lower altitudes.
Bloom-time petiole sampling is a good tool for those interested in learning more about the nutritional status of their vineyard. This may be of particular interest to those who (1) have annual historical records of bloom-time vine nutritional status, (2) want to establish a baseline of vine nutritional status, and/or (3) are looking to correct historically observed foliar nutritional deficiency symptoms (foliar nutrient symptoms are rarely observed this early in the season, excepting maybe in young vines, or newly-planted vineyards). Remember that vine tissues are one part of the “vineyard nutrition equation” – the other part being the soil. Soil mineral nutrient analyses can be accomplished through soil sampling and analysis.
There are plenty of sources that outline proper petiole sampling procedures (see the bottom of this post), so I’ll be brief here. Petioles should be collected from opposite a cluster on the primary shoot. The amount of plant tissue needed is dependent on the size of the petiole, which is often a function of variety. However, 80-100 petioles per composite sample will suffice. Keep all composite samples separate based on variety and rootstock combination, vine age, observed differences in vine growth/vigor, soil type, soil topography (i.e. distinct sloped vs. flat vineyard sections), and generally “healthy” vs. “unhealthy” vines.
Please work with your county extension agent to collect and process petiole samples.
Petiole samples can be sent in to many labs, but I would encourage that samples be sent to one of our Viticulture Extension Team Members: Dr. Jay Lessl. Expect Dr. Lessl to soon post information on the variety of services he and his lab at UGA can offer vineyard and winery stakeholders, such as fruit and wine compositional analyses and soil analyses.
Send petiole samples to:
Soil, Plant, and Water Laboratory
2400 College Station Road Athens, Georgia
30602-9105
Website: https://aesl.ces.uga.edu
Further reading on petiole sampling (some including deficiency and toxicity tables for petioles and leaf blades):
https://www.smallfruits.org/BunchGrapes/production/TissueAnalysisforGrapevines.pdf
https://gwi.missouri.edu/publications/procedures-for-petiole-sampling.pdf
https://articles.extension.org/pages/31517/monitoring-grapevine-nutrition
