A & L Western Laboratories Oregon and california

Plant Analysis

Collecting the Plant Tissue Sample

Generally, about a pintful of plant tissue is sufficient for each sample, or about a cupful if dealing with petioles. Consider sampling at different stages of growth, or annually, to monitor trends. Collect from 10 to 20 locations within a selected area: a sufficient number to "average" out variations.

A basic knowledge of plant structure is necessary before collecting samples. A leaf is made up of a leaf "blade" and a "petiole". The petiole is the stalk attached to the blade. It is the preferred plant part sampled in grapes. Petioles are sampled in many vegetables and crops such as cotton and sugarbeet, when determining nitrate-nitrogen levels through the growth of the crop. "Midribs" are the middle ribs to large leaves such as corn, lettuce, and cabbage, and would equate to a petiole sampling. A compound leaf may have several "leaflets" attached to it. In some cases, only terminal "leaflets" may be sampled, as in the case of walnuts and pistachios. A common error in tomatoes is when only leaflets are sampled instead of the whole compound leaf. This shows the importance of understanding proper sampling technique. In general terms, "most recently matured" plant tissue should be selected.

Sample Information:

Identify each sample with numbers and/or letters, by row number or field for example, or good versus bad. Avoid numbering samples simply as 1,2,3 … as it may lead to confusion later. Indicate the analysis desired and provide very specific information on stage of growth and plant part if an interpretation is required. Select either the standard format (three samples per page) or the graphical format (one sample per page). Refer to A & L's list of available plant codes. The laboratory does not automatically provide an interpretation, as some clients prefer to make their own.


If samples are very wet, air-dry to a workable condition before packaging. Otherwise, decomposition or molding will occur. Include a completed plant analysis information sheet or cover letter with instructions within the same package. Processing will be delayed if sent separately. Also, include payment if you do not have an established account.
Samples should be shipped by a carrier such as UPS or FEDEX, or by first class mail.
Caution: Do not submit sick-looking plant tissue for a nutrient analysis only. It may be necessary to request a pathology assay or a pesticide residue test also. Seek further advice.

Send Samples to:

A & L Western Agricultural Laboratories, Inc.

California Office:
1311 Woodland Avenue, Suite 1
Modesto, CA 95351
Phone (209) 529-4080
Fax (209) 529-4736

Oregon Office:
10220 S.W. Nimbus Ave., Bldg. K-9
Portland, OR 97223
Phone (503) 968-9225
Fax (503) 598-7702

Please follow these simple instructions if ratings are required:

  1. Always enter "crop" or variety (up to 14 characters).
    1. The standard report provides data and ratings in a numeric format. At the bottom of the report the average of the sufficiency range is reported as a norm for the indicated crop. For this reason, do not include more than one crop per report.
    2. The graphical report form is limited to 1 sample and 1 "crop" per page. Therefore, order of crops listed is not important in this case.
  2. Enter the growth "stage" and plant "part" sampled (see options under crop).
  3. Enter your sample reference, such as field # (up to 5 alphanumeric characters).

    e.g. Sample ID: 23-SB ZINFANDEL BLM P = Zinfandel grapes sampled at bloom stage and petioles were sampled. (Note that rootstock may have an impact though.)

For a complete list of crops and information regarding sampling at different stages of growth, click here.