How to Submit Plant Tissue Samples

Why Should I Do Plant Tissue Analysis?

Plants require a steady supply of essential mineral nutrients for optimum growth and development.  A shortage of any nutrient can result in poor crop quality and reduced yields.  Plant tissue analysis, used in combination with soil testing, is an excellent way to develop an overall soil management program while monitoring plant health and fertility.

While soil testing determines the nutrient status of the soil, plant tissue analysis shows how well crops are recovering those nutrients from the soil.  “Hidden hunger” and visual deficiency symptoms can be verified, pinpointing which nutrients plants need.

Before You Begin – A Few Words About the Importance of Proper Plant Sampling Techniques:

The plant tissue sample collection process varies from plant to plant.  To take the guesswork out of the collection process, we have provided detailed information in the “What to Sample” and “How to Sample” sections below.  In addition to providing some plant illustrations, we have included reference tables giving crop-by-crop specifics on when to sample, which parts of the plants to take, and how many samples are needed. 

As background, here are a few basics on leaf structure.  A leaf is made up of a leaf “blade” and a “petiole.”  The petiole is the stalk attached to the blade.  A compound leaf may have several “leaflets” attached to it.  In some cases, only terminal leaflets may be sampled, as is the case of walnuts and pistachios.  A common error in testing tomatoes is when only leaflets are sampled instead of the whole compound leaf. 

 Leaf Structure

The most recent mature leaf (MRML) is the first fully expanded leaf below the growing point.  It is neither dull from age nor shiny green from immaturity.  For some crops, the MRML is a compound leaf.  For example, the MRML on soybeans and strawberries is a trifoliate compound leaf, or three leaflets comprising one leaf.

In some crops such as cotton, grapes, potatoes, and strawberries, the petioles provide additional indications of nitrogen status.  When these crops are tested, the petioles are used, in addition to the MRML.

When to Sample:

The best time of day to collect samples is between midmorning and midafternoon.  Sampling during damp conditions can be done but requires extra care to prevent plant tissue from decomposing during shipping.  

To monitor plant nutrient status most effectively, sampling should be done during the recommended growth stages for the specific crop. During critical periods, samples should be taken weekly or biweekly, depending on management intensity and crop value.  However, to identify a specific plant-growth problem, samples should be taken whenever a problem is suspected.

What to Sample:

Proper sampling is the key to reliable plant analysis.  A sample can represent the status of one plant or 20 acres of plants.  The appropriate part of the plant to sample varies by crop, stage of growth, and purpose for sampling.

When sampling for problem solving, take samples from both “good” and “bad” areas.  A comparison between the two groups of samples will help to pinpoint the limiting element(s).  This comparative sampling will also help to factor out the influence of drought, stress, disease, or injury.  Soil samples from the root zones of both “good” and “bad” plants should be taken for the most complete evaluation.

What to Sample (Continued):

When sampling for monitoring the status of healthy plants, take samples from a uniform area.  If the entire field is uniform, one sample can represent a number of acres.  If there are variations in soil type, topography or crop history, take multiple samples so that each unique area is represented by its own sample.

When sampling seedlings less than 4 inches tall, take whole plants from 1 inch above the soil line.  For larger plants, the most recent mature leaf is the best indicator sample.

The table below provides crop-by-crop specifics on when to sample, which plant parts to collect, and desirable sample sizes:

*  Information about many other floricultural plants is available upon request.

How to Sample – Illustrations to Assist You in Taking Samples:

 click image to enlarge

click image to enlarge

Getting Started – The Materials You Will Need:

• Plant Tissue Sample Information Form (enclosed/attached - use1 per sample)
• Paper bags, envelopes, or cloth bags (Do Not mail samples in plastic bags)
• Clean plastic pail (Do Not use galvanized or metal containers)
• Clean, dry soft brush or clean cloth
• Distilled or deionized water

Taking Samples – Step-by-Step Collection Instructions:

Step 1

Fill Out Plant Tissue Sample Information Form(s)

Fill out a separate Plant Tissue Sample Information Form for each sample you are submitting.  Be sure to complete this form in as much detail as possible.

• Note any relevant conditions such as drought, disease, injury, pesticide, or foliar nutrient applications. 
• Provide very specific information on stage of growth and plant part.

The more information you provide on this form, the more accurate our recommendations to you will be.

Step 2

Collect Samples

Using the tables/illustrations provided in the “What to Sample” and “How to Sample” sections, collect representative samples of the leaves and petioles for your particular crops/plants. 

• Determine how many samples to collect & what part of the plant to sample from the      “What to Sample” section.
• Collect the tissue samples in a clean plastic pail, paper bag, or cloth bag.  Do not use galvanized or metal containers.
• Detach leaves from petioles in the field to stop the translocation of nutrients.  

(Note:  “Midribs” are the middle ribs of large leaves such as corn, lettuce, & cabbage, and would equate to a petiole sampling)

• Put petioles in a separate bag.
• Avoid sampling plants that are damaged by disease, insects, or chemical applications.
• Do not include dead plants or plant materials in the samples.
• Do not sample very young emerging leaves.
• Do not sample old mature leaves or seeds unless their condition is the purpose of analysis.
• Avoid plants under stress from moisture or temperature extremes.
• When sampling seedlings less than 4 inches tall, take whole plants from 1 inch above the soil line. 

Step 3

Clean the Plant Samples
 (if needed)

Samples must be kept free of soil & other contaminants that can alter results.  If the plants have soil, fertilizer, dust, or spray residues on their surfaces, wipe them with a clean, dry, soft brush.  A damp cloth along with distilled or deionized water may be used for samples containing excess residues.  Be careful not to prolong the washing as some nutrients may be removed from the plant. 

Step 4

Air Dry the Plant Samples

To prevent decomposition and molding, air dry the plant samples before packaging.

Step 5

Pack Samples for Shipping

Put the air-dried samples in paper bags, envelopes, or cloth bags for shipping. 

Note:  Do Not send samples before they have been air dried.  Do Not use plastic bags for shipping.

Step 6

Label Bags/Envelopes

Using a permanent ink pen or pencil, clearly label each bag with your name and address.

Using up to six letters or numbers, give each sample a unique identifier that will help you remember the plant or area it corresponds to such as HOUSE1, 15B, GOOD, or BAD.  Write the identifying numbers/letters on the envelopes/bags and the Plant Tissue Sample Information Form.

Keep a record for yourself of the location represented by each sample.

Step 7

Pack Plant Samples for Shipping

Place all plant samples in a sturdy container.

Step 8

Seal Shipping Box

Before sealing the container, enclose one completed Plant Tissue Sample Information Form for each sample submitted and a check payable to Timberleaf Soil Testing for the number of samples enclosed.

Step 9

Mail Box to Us

Send all soil samples & communications to:

Timberleaf Soil Testing
39648 Old Spring Road  
Murrieta,  CA  92563

Phone/Fax  (951) 677-7510
E-mail  tmbrlfsoiltest@verizon.net