Grape nutrients play a critical role in overall vineyard production. They contribute to balanced vegetative growth and yield production. They can also improve fruit quality and enhance vine cold hardiness and longevity. This makes monitoring and managing soil and plant nutrients extremely important for optimal vineyard efficiency.

A soil test typically measures how much of each nutritional element is currently present. It also provides information on other factors—such as organic matter content, soil pH, and cation exchange capacity—that are important to know when making management decisions. Deficiencies that are seen in these tests can then be dealt with by supplementing the soil with different amendments. Soil tests are usually recommended prior to planting a new vineyard and then every three years. However, soil testing alone does not adequately signal the nutritional needs of perennial crops like grapes. Vine tissue testing is the preferred method to monitor nutritional needs, identify problems such as mineral deficiencies, and manage fertilization practices to maintain plant health.

Collecting Tissue Samples

Growers should collect separate tissue samples from each grape variety and rootstock combination in their vineyard. Typically, a tissue sample should not represent an area more than 10 acres. There are two growth stages when growers can collect tissue samples for testing: during bloom and during veraison.

During Bloom

The first option is during bloom, when about 60 to 70 percent of the flower caps (calyptras) have fallen (figure 1). Grape bloom time may vary depending on several factors, including location, cultivar, and management practices. So, it is important to monitor the vineyard and consider tissue sampling for nutrient analysis. For the 2025 growing season, grapes are developing on schedule in Alabama and fruit-cluster blooming is fast approaching.

When collecting samples during bloom, collect 60 to 100 petioles (the stem that holds the leaf blade to the shoot) from leaves positioned at the same node as the cluster (figure 2). Place the sample in a clean paper bag and label it to identify the cultivar, location, and date of sample collection.

During Veraison

The second option for tissue sample collection in your vineyard is during the veraison stage, when approximately 50 percent of berries have colored as they mature (figure 3). When collecting samples during veraison, collect 60 to 100 petioles and/or leaf blades from recently matured, fully expanded leaves on the shoot. These are typically located five to six leaves back from the shoot tip. Place the sample in a clean paper bag and label it to identify the cultivar, location, and date of sample collection.

Submitting Tissue Samples

To submit samples for testing, complete the needed form and mail the sample, form, and payment to the Auburn University Soil, Forage, and Water Testing Laboratory. Visit aaes.auburn.edu/soil-forage-water-testing-lab for more information.