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NC State Extension

Submitting Samples From Plants in a Greenhouse

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potted floriculture plants in a greenhouseA good sample is essential for an accurate diagnosis. Please follow these instructions carefully. The instructions on this page apply to sampling plants grown in greenhouses, either for harvest or for sale as transplants.

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To sample for disease diagnosis

  • Roots, stems, foliage, and – if applicable – fruits should all be included.
    • Small plants: submit several plants, representing a range of symptoms.
    • Large plants: submit one or two whole plants with moderate symptoms.
    • Very large vines: submit one or two root systems, still attached to the bottom 8”-12” of the main stem(s), plus representative sections of the rest of the vine.
  • Plants can be sent in the original container (cell pack, flat, float tray, pot, or bag) or separately. Removal from the pot is often a good choice when roots have not yet filled the pot.
  • Plant foliage should be dry and planting medium should be slightly moist but not soggy. In the case of float trays, allow them to drain before shipping. 
  • Take precautions so that potting media does not spill on foliage in transit. In most cases this means wrapping the root system in a plastic bag fastened loosely around the base of the stem. Do not shake off media immediately around the roots, as it protects them in transit. 
  • Potting media is also used in some tests. We prefer to receive about a quart of media. If that quantity is not available around the roots, additional media can be sent in a separate bag.
  • Place the entire plant(s) in an additional plastic bag and seal. Do not add water or wet paper towels.
  • Ripe fruits and vegetables should be packed in absorbent material. They should not be bagged, unless being sent from outside of North Carolina, in which case double-bagging is required.
  • Keep samples out of the sun, preferably refrigerated, until they can be shipped or taken to the clinic.

In addition to the physical sample, a few photographs showing the symptoms of concern and their distribution in the greenhouse can be helpful to the diagnosticians. These can be uploaded to the database along with the sample information.

Pathogen detection in planting material

While we understand growers’ concern that seeds, plugs, or liners may harbor pathogens, we do not as a general rule accept samples of plants or planting material that appear to be healthy. This is for three reasons. First, there are dozens of potential pathogens, so we need the symptoms as a guide for the diagnostic process. Secondly, when pathogens are present without symptoms, they tend to be at low levels, requiring particularly sensitive screening techniques. Third, the selection of the sample is critical in those cases, to reduce the chance of a negative result that doesn’t truly reflect what’s going on in the greenhouse or nursery. If you have any specific questions about this policy, feel free to contact us at 919-515-3619 or via email at