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view of bunchgrape blossoms

Despite the unusually cold spring weather, grapes are developing on schedule and fruit cluster blooming is fast approaching (Figure 1). Grape bloom time may vary depending on several factors including location, cultivar, and management practices, so it is time to monitor the vineyard and consider tissue sampling for nutrient analysis.

bloom with 10% open flowers on a bunch grape

Figure 1. Beginning of bloom with 10% open flowers on a bunch grape grown at the Chilton County Research and Extension Center.

Why to sample?

Understanding grapevine nutrition and managing nutrient needs of the vineyard is vital for sustainable grape production. Soil testing alone does not adequately signal nutritional needs of perennial crops like grapes. Vine tissue testing is the preferred method of monitoring the plant’s nutritional needs and identify problems such as mineral deficiencies or manage the fertilization practices to maintain plant health.

Where to sample?

Collect separate tissue samples from each grape variety and rootstock combination in your vineyard. Typically, a tissue sample should not represent an area over ten acres.

When to collect tissue samples?

There are two options to consider for sample collection. The first option is during bloom, when about 60 to 70% of flower caps have fallen. Collect 60 to 100 petioles from leaves positioned at the same node as the cluster. Place the sample in a clean paper bag, label to identify the cultivar, location, and date of sample collection. Take the sample to your county extension office or mail to Auburn University Soil Testing Lab. Find the mailing address and other information on the soil lab website http://www.aces.edu/anr/soillab/.

The second option for tissue sample collection is during veraison stage (50% of berries colored as they mature). Collect 60 to 100 petioles and/or leaf blades from recently matured, fully expanded leaves on the shoot, typically located 5-6 leaves back from the shoot tip.

Additional Resources

Read more about Monitoring Grapevine Nutrition: https://grapes.extension.org/monitoring-grapevine-nutrition/

Read more about Tissue Sampling for Vineyards: https://extension.umd.edu/resource/tissue-sampling-vineyards