After doing the planting and tilling that’s involved in industrial hemp cultivation, the next step is to harvest your crop. Congratulations on getting this far, it is no small feat.
Is there one special trick to harvesting industrial hemp successfully?
Yes, there is a magic formula that will set you off on the right path, which is getting the timing right. When you need to harvest depends on how you intend to use your hemp. Harvesting too early or too late will keep you from utilizing your hemp’s full potential.
You also need to harvest industrial hemp when the temperature and relative humidity are perfect. If there is too much moisture the hemp will be prone to bud rot, but if it’s too dry the stalks may not be easy to work with. Moisture easily gets trapped in the center of the stalks causing a “closed umbrella” shape, which is why it’s important to open up the stalks to encourage even drying.
Industrial hemp needs to be dried and cured at warm temperatures. If you wait too long before you harvest you might not be able to adequately dry your hemp, which is bad because improperly dried hemp has a lower value. Molds and mildews on hemp plants will also cause their value to go down.
One of the most accurate ways to predict the time for harvest is to look at the resin buds, or trichomes, on the surface of the buds. If they have turned from transparent to milky white it means that harvest time has come. The trichomes carry the cannabinoids and terpenes, and when they are mature it means that cannabinoid levels are at their peak. If you have a large grow, consider investing in CBD testing equipment. The weather can also tell you when to harvest.
Lastly, remember to harvest when labor is readily available and cheap.
The Harvesting Process
You should begin harvesting hemp fiber when the seeds start to turn brown. If you wait too long, the fibers will become too coarse and the male fibers will begin to die. The fibers and seeds may mature at different times, so it is up to you to prioritize between the two if this happens.
Once you have determined that your crop is ready for harvest you should start by cutting the hemp stalks with a sickle or sickle-bar mower. For small grows, cut the stalks close to the base of the plant with a sickle, but for larger grows consider using a sickle-bar attached to a tractor.
After cutting down the stalks you should leave them to dry in the field for 4-5 weeks. Pile the stalks on top of each other to allow moisture to seep in. This will make the retting process easier because moisture breaks down chemical bonds in the fiber, making it easier to work with. This is why you should not allow your stalks to dry too much. Retting can also be done by dipping the stalks in a little water for 10 days, and it ideally takes place at temperatures below 41 °F (5 °C) or above 104 °F (40 °C).
After retting, let the stalks dry until the relative humidity level is between 10% and 15%.
Decortication is done using a decorticator machine. This is the process of breaking up the stalks to separate the fiber from the waste material.
You should harvest industrial hemp after about 16 weeks. By this time, the seeds should be mature and brown with hard husks. Most of the leaves should have fallen off by this time as well.
In the U.S., most industrial hemp is ready for harvest by early October. Look out for seeds that have not matured, and if there are a lot of them then you can delay your harvest until they are more mature. You can leave the fallen leaves on the ground so they can add organic manure to the soil.