One of the risks in farming hemp is the very real possibility of one's crop going "hot" and then being required to destroy it, watching 8 months of hard work get plowed back into the ground. "Hot" is when a hemp plant produces more than 0.3% delta-9 THC. That tiny percentage is the threshold where hemp becomes marijuana and thereby illegal for me to grow or possess.
Understanding what causes a hot crop and working to avoid it are critical steps, but, just as important is knowing when to harvest, because most CBD hemp strains will eventually produce too much delta-9 THC if not harvested early enough. But the window between when a plant has produced sufficient CBD for harvest and when it will go hot is only a few weeks at best. The key to timing this just right lies in watching the plant's trichomes.
Trichomes are structures that form on the flowers and sugar leaves (leaves that sprout in the vicinity of flowers) of the hemp plant. They are typically shaped like small mushrooms or whiskers. You can see them in the title photograph for this blog entry above: thin stalks with a ball on top and mostly a milky white in color.
The trichomes start out clear and then turn a milky-white as they fill with resin. That resin is where the CBDA that we will convert to CBD is created. All of our extraction methods are about getting that resin out of the trichomes.
After the trichomes have turned an opaque white they then start to turn amber. The point when the trichomes are turning amber is the ideal time to harvest. Unfortunately, Ohio hemp farmers don't get to harvest at exactly the right moment because we have to have a representative from the Ohio Dept of Agriculture come out and take samples for potency testing in order to make sure we're not hot. That process can take two weeks. Or it can take two days. Once the samples are taken you have 10 days to harvest, so from the time you call for tests it's anywhere from 12 days to 24 days until you have to have completed your harvest.
If all works out right, they take the samples while the trichomes are still white in order to keep any THC low and then they turn partially amber within a few days before you harvest. Late samples mean higher CBD concentrations, but also more THC, so it's wise to err on the side of caution and harvest early.
The scrolling photos above include two of our CBG strain, Grail which, has white trichomes all over and one photo of our Merlot CBD strain which is just getting started at growing it's trichomes. Probably another 4 to 5 weeks before we harvest the Merlot while we start harvesting the Grail once the testing is done.