As a benefit of membership, NDGWA members will receive three petiole tests for free.
The best time of the year to check the nutritional status of our vines is when the grapes begin to flower. Veraison is the other time. Bloom time sampling can be used to make in-season fertility adjustments, while sampling at veraison is used to evaluate one’s overall fertility program.
Collect only one petiole per shoot. Each sample should consist of 100 petioles so the lab has sufficient material to test. For bloom time sampling, take the petiole closest to the cluster. At veraison, take the petiole of the last fully expanded leaf. Wrap the samples in a dry paper towel (NOT PLASTIC) and mail to:
PO Box 510
Northwood, ND 58267
Include a note with your name, the grape variety, sampling date, and a request for a “complete tissue analysis including total nitrogen”.
How to collect petiole samples: Information from Univeristy of Minnesota
YouTube video on petiole sampling:
The cost for petiole testing is ~$32.00 each.