How To: Collect plant samples
Sooner or later, every grounds-care professional requires the services of a plant laboratory. The two basic reasons for submitting plant samples are to obtain a nutritional analysis and to diagnose a disease problem. The type of sample you take will depend on which of these is your objective: Nutritional analyses typically require you to collect foliar samples, while disease diagnosis may necessitate more extensive sampling.
Cooperative-extension services and private laboratories have the expertise and equipment to provide meaningful diagnoses, but their services only can be as good as the samples you send them. In fact, sample quality often is the weakest link in the diagnostic process. Following proper sampling procedures ensures accurate and useful results from your laboratory. The key is providing a fresh, intact sample. The procedures below are adequate for most samples, but be sure you comply with any instructions your lab gives you.
Foliar nutritional sampling If your turf or landscape plants are showing deficiency symptoms, it's helpful to sample from healthy plants as well as affected specimens. That way you can correlate visible symptoms with lab results and confirm or eliminate suspected causes. In addition, you also should have your soil analyzed. This allows you to determine whether a nutritional problem is due to soil deficiency or poor plant uptake.
* For turf, use hand clippers to collect about 1 quart of clippings at least 2 days after the last mowing. In addition, take the sample as long after your last nitrogen application as possible. You also can use clippings from your mower, but make sure the sample is free of weeds, dead leaves and other contaminants.
* For ornamentals, sample recently matured leaves (avoid newly formed or old leaves) and remove large petioles and stems. Again you'll need about 1 quart of leaves, ideally from several regions of the plant.
Ensure that foliar samples are air dry (free of dew or other surface moisture). Then place them in paper bags (labs often provide these for you). Do not use plastic bags, which quickly can cause samples to rot.
Disease-diagnosis samples Do not apply pesticides before collecting samples, because this could kill the organisms, such as fungi, that you are trying to identify, possibly rendering identification impossible.
* Turf. Turf samples should be about 5 inches square and at least 3 inches deep to include roots and soil. A cup cutter is a good tool for this purpose. Collect samples from areas in several stages of disease development, and especially make sure you include samples from transition areas between healthy and diseased turf. Keep the soil-and-root layer intact. Wrap the soil and roots--but not the grass blades--in aluminum foil.
* Ornamentals. Woody and herbaceous ornamentals are easier to diagnose with large-size samples, so send the largest sections of the plant that you can. Shoot sections from woody plants should be at least 6 to 8 inches long. Further, provide as many portions of the plant as possible, including flowers, fruit, leaves and roots. If the specimen is small enough, include the entire plant. Just be sure to shake excess soil from the roots and wrap the plant in a manner that prevents soil from contaminating the foliage. Use newspaper or paper towels for wrapping, and ensure that the sample is air dry. As with turf, be sure to include samples of areas that are transition-ing from healthy to diseased.
* Provide complete information. An important part of submitting a sample is recording as much site information as possible. For example, you should include a description of the progression of symptoms, the plant's identification, site factors such as soil, water and exposure, age of the planting, site use, fertilizer- and pesticide-treatment history and other information that could have some bearing on the plant's condition. This is vital for diagnosing diseases. Typically, labs supply clients with forms that ask for such information, but be sure to note any peculiar factors not specifically requested, and even send photos if you have them. If you do not have a form from the lab, supply all relevant information anyway.
Shipping Proper shipping is an important aspect of submitting samples. Never pack turf or ornamental samples in plastic unless you can deliver the sample by hand or with an overnight service and can confirm that a technician will open the sample immediately after it arrives at the lab. If not, use paper bags, paper towels or newspaper. Use sturdy packaging that will protect the sample from damage during shipping. Overnight shipping is preferred, but if you do use regular mail, send the sample early in the week. Late-week mailings run the risk of sitting in a warm post-office over the weekend.
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