It is time for tissue sampling in grapes.  Student workers were taking samples today in our research vineyards, as we are in full bloom in the Athens area.  I suspect that the bloom will vary by variety and location, but all of us are close.  I am providing more information than you might want for this operation, but this is important.  Please take a look at the following, and I am hopeful that it will be of service for you now and in years to come.

If you have been using mancozeb or copper fungicides, this will result in false readings (high) for zinc, manganese and copper. In order to obtain accurate readings for these nutrients, you will need to wash petioles and/or leaves before shipping them to a lab for analysis.  The Plant Analysis Handbook says to “wash in a mild detergent (0.30 percent) and rinse in running water to remove most attached substances. Do not prolong the washing procedure or allow the plant material to “stand” in either the washing or rinsing baths. Wash and rinse briskly. Wash leaves which have been sprayed with nutrient solutions while they are still fresh.”  Another reference also indicates that leaf samples should be washed prior to shipping for best results.  A 1 to 2% soap solution, not containing any of the nutrients to be analyzed, should be used to remove residue from the leaf and petiole surface.  After washing, samples should be air dried prior to shipping. Wet petioles or leaves can be rotted by fungal and bacterial organisms during shipment, and that could influence results. 

For best results, use a fresh sample prior to shipping.  Ship overnight in a paper bag (not plastic to prevent sweating of the tissue in the bag). You can send tissue samples through your county extension office.  They go to the following location in Georgia, and you can call the lab directly if you need additional answers.  The lab indicates it is helpful if you send more petioles/leaves than required. 

Soil, Plant, and Water Laboratory

2400 College Station Road

Athens, GA 30602-9105


Courtney Cameron and Kendall Busher, two undergraduate students working with me this summer, looked up the following information for sampling this morning, and these are good references.

Tissue sampling for Vinifera and hybrids:

  • “Tissue to sample for the bloom sampling period, sample the petiole of the leaf petiole OPPOSITE the 1st blossom/cluster”     
  • “About 50-75 petioles are needed from varieties with large petioles and about 75-100 petioles are needed from varieties with small petioles.”
  • “Gently wash petioles with water and gentle detergent to remove any residual pesticide that may influence results.”

Muscadine Sampling:

We may be early for sampling muscadines in some parts of the state, but the south Georgia vineyards will need samples now or very soon.  A good reference can be found at this website.

  • “ Collect leaf blades located opposite fruit clusters. For muscadine tissue samples, submit only leaf blades.”
  • “A good sample consists of 25 to 60 leaf blades. These should come from the most recently mature leaves (MRMLs), which are usually located opposite the fruit clusters (five to seven leaves from the shoot tip). Do not collect more than one or two MRMLs per vine.”

For muscadines, you should also reference the new regional guide:

But wait, there is more! The following information was provided by Jay Lessl in a previous blog post, and it may also be of use to you, especially for Vinifera and hybrid grapes.  

Plant Tissue Analysis

Plant tissue analysis for grapevines, which involves testing the petioles or leaf blades, is the preferred method of monitoring the nutritional health of vineyards. Tissue analysis may be done for two reasons: the first is troubleshooting to confirm or deny a suspected nutrient problem within the grapevines, and the second is to monitor nutrient levels within the vines to detect a nutritional problem before it negatively impacts yield and fruit quality.

What to sample and how much

Analysis of petioles (~60-100 petioles) or leaf blades (~20-40 leaves) will give a reasonable estimation of nutrient status.  However, petiole analysis best indicates the current movement of nutrients towards the leaf blade (nitrogen, phosphorous, potassium, and magnesium).

Site Selection

Samples should be taken from a single management area and should represent one single variety/rootstock that is maintained under the same cultural practices (i.e., fertilization, irrigation, and pruning).  Generally, a tissues sample should not represent an area over 10 acres.

When to Sample:

Suspected Nutrient Problem: When troubleshooting nutrient deficiencies, collect petioles or leaf blades any time during the season from symptomatic leaves regardless of their shoot position.

Bloom: When ⅔ of the flower caps have been shed, collect petioles from leaves located opposite the first or second flower cluster from the bottom of the shoot. Bloom time is especially important because insufficient levels of micronutrients can have a season-long effect on fruit quality.

Véraison: Collect petioles from the youngest fully expanded (mature) leaves on the shoot, usually located from five to seven leaves back from the shoot tip. Sampling at veraison may provide a more accurate assessment of the status of other elements. Due to the timing, adjustments to be made to the fertility program will be applicable to the next growing season.

Handling Samples

Place in a clean paper bag and label with appropriate information so that when you receive the report, you can easily identify the variety, location, growth stage, and date. The samples should be taken to your local county extension office as soon as possible.

Plant Test Descriptions & Fees

Standard Plant Tissue: $25.00 + shipping

The report includes N, P, K, Ca, Mg, S, Mn, Fe, Al, B, Co, Zn, and Ni along with sufficiency ranges for nutrients.

For additional information or questions, contact:

Jay Lessl


I hope all of this will be of value to you as you consider tissue sampling over the next week or two. Hang in there and stay safe!

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