When flowers are filling out and the hemp harvest is around the corner, it's time to consider preharvest testing. The key details of the Oregon Department of Agriculture’s preharvest testing process for hemp can be found online.
You’ll find an excellent webinar detailing the preharvest testing process. Emily Roque, ODA’s hemp testing specialist, explains the protocol and how to complete the request form. If you’re new to growing hemp in Oregon or feeling rusty on the process, it’s worth a watch. See an example of a completed “Hemp Sampling Request” form.
New and updated requirements for 2022
- All harvest lots must be a single hemp strain/variety. Each strain you plan to harvest must have its own pre-harvest test.
- Harvest must be complete within 30 days from the date of sampling or the grower must arrange for additional sampling of the unharvested hemp.
- A sample will fail the preharvest test when the application of the measurement of uncertainty to the amount of total THC of the sample calculated in accordance with OAR 333-064-0100(4) reported by a laboratory produces a distribution or range that does not include 0.3 percent or less on a dry weight basis. See Figure 1.
Some strains of hemp may accumulate total THC content above 0.3% by the time they reach maturity. This pattern of cannabinoid accumulation has been documented in research conducted at Cornell University. Conducting the preharvest test in the first several weeks after flower commences will reduce the chances of CBD hemp testing above the THC threshold.
Research conducted in southern Oregon in 2020 and 2021 found a pattern of cannabinoid accumulation similar to that described in the Cornell paper. The results of that study were presented at the Southern Oregon Hemp Growers Forum (timestamp 1:12:30).