How to Collect Leaf Samples

The objective of plant sap testing is to asses and resolve stress, pests, or toxicities. Sap analysis provides valuable data for making fertilizer recommendations. Foliar applications address nutrient deficiencies until desired health is achieved.

Obtain optimal plant health by conducting 5-7 Leaf Extract Analyses throughout the growing season.



7:00 am - 9:00 am

Always sample at a consistent time of day, preferably prior to 8 am to ensure minimal transpiration


Preferably dry weather. Avoid rain or dew on the samples—dry them off with a paper towel if necessary.


Collect a representative field sample including one new and one old leaf from at least 20 vines of the same cultivar and growing conditions. Each sample (new and old) should fill a 1qt plastic bag.

Sample NEW leaves and OLD leaves SEPARATELY and place them into individually labeled bags.  

  1. New = newest recently-mature leaf from the top of the plant. The MRML will usually be the fifth leaf from the tip.
  2. Old = oldest still-viable growth from the bottom of the plant.

For each sample, pull leaves from as many plants as realistic within the block being tested. 20 leaves is usually sufficient. Stick to testing a single cultivar at a time.

Avoid the outer rows in the field, and the first and last 10 yards in a row.

Sample leaves of average quality (abnormal plants should be tested separately).

Sample from the same side of the plant if there is a sunny/shady side of the plant.

Cut off the petioles (they contain different levels of minerals than the leaves).

Ensure samples are as clean as possible - dew, dirt, dust, and fertilizers can affect test accuracy. Rinse the leaves with clean, non-chlorinated cold water.

Ensure samples are surface-dry (not dried out) before bagging - dew, rain, and condensation affect accuracy.

If samples are not dry, please dry with paper towel or air dry to ensure leaves are not wet in the sample bag. 

Complete a Sampling Label with your contact info, crop, cultivar, field/block info, new/old leaf, and desired agronomy services. Affix labels to the outside of each sealed plastic sample bag. (Do not use paper bags or include paper in bags)

Keep samples viable by minimizing shipping time and using cold-packs and/or insulated packaging when shipping leaves in warm conditions. Wrap frozen cold-packs in paper to insulate them from direct contact with samples.

Mailing procedures

Use USPS express mail. A mailer box will be provided for you.

Remove air from the ziplock bags prior to sealing the bags.

Send the sample either Monday or Tuesday before 12pm. Samples sent after Tuesday will not be processed until the following week.

Print and complete the labels on the attached form and attach them to the Ziploc bags. Ensure the chain of custody form accompanies the samples in the mailer box.

If temperatures are hot, including a disposable ice pack in the package will guarantee quality results.