Collect petiole samples from vinifera vineyards during full bloom.
To monitor the nutrient status of vinifera grapes, collect a tissue sample during full bloom. The sample should consist of at least 50 petioles collected from leaves opposite the first or second bloom cluster from the bottom of the shoot. Collect petioles randomly from throughout the vineyard. Do not collect more than two petioles per vine. Place the sample in a paper bag or envelope. The plant tissue report will let you know if your fertilization program is meeting crop needs.
If you want to use tissue testing to diagnose a suspected nutrient problem, collect a petiole sample as soon as you see symptoms. To troubleshoot a problem, you should collect four different samples: 1) a petiole sample from symptomatic leaves, 2) a similar petiole sample from healthy plants, 3) a soil sample from the problem area and a soil sample from the healthy area. Sample forms and sampling instructions are available at www.ncagr.gov/agronomi/sampleinfo.htm. There is a $7 processing fee for each grape petiole sample.