(This is the 13th installment in a series focused on cultivation planning for marijuana and hemp growers. The previous installment is available here.)
Both indoor and outdoor marijuana and hemp growers can give themselves a leg up by thinking ahead when it comes to arguably the most crucial step in the entire cultivation process: harvest.
Cultivators aiming to dial in their harvest techniques should consider the following:
- Have a plan to test crops to determine cannabinoid content and when to cut them down.
- Know that defoliating plants early can mean less plant handling later.
- Determine whether flushing out nutrients a couple weeks ahead of time is necessary.
- Prepare a clean, climate-controlled space for storing material.
The old method of eyeballing trichomes for the correct color as they shift from clear to opaque to amber might still work as an indicator of when to harvest, but there’s a more scientific way.
Either using on-site testing or sending the plant to a third-party lab is the most accurate way to ensure the crop is ready.
Growers need to determine when to harvest based on potency, said Travis Higginbotham, vice president of production for Harborside Farms, based in Salinas, California.
The marijuana market wants 22% THC or more, he said. So plan to send representative samples – one per cultivar – to a lab up to a week ahead of time, and if they don’t hit that potency mark keep growing.
Harvest on the Northeast Kingdom Hemp farm in Barton, Vermont. (Photo courtesy of Northeast Kingdom Hemp)
For Karen Devereux, co-owner of Northeast Kingdom Hemp based in Barton, Vermont, testing hemp before harvest is crucial.
That’s where the company’s on-site, high-performance liquid chromatography testing comes in handy.
“We want to make sure we’re getting the CBD level as high as we can but not letting the THC level get too far,” Devereux said.
If you decide to go the old-school route of just looking for indicators from the plant that it’s ready, Brie Kralick, director of cultivation operations for Hava Gardens, based in De Beque, Colorado, recommends looking at the pistils rather than the trichomes.
Trichomes can look cloudy – which some growers say is the time to harvest – but they can also revert to clear, according to Kralick.
Instead, she likes to check for color in the pistils on the buds.
“If the majority of the pistils are more orange, it’s mostly finished,” Kralick said. “If not, you have more time.”
Another way to save some time during harvest is to defoliate while the plants are still alive.
That’s what employees do at Jushi Holdings, a multistate marijuana company with headquarters in Boca Raton, Florida.
Josh Malman, vice president of cultivation operations for Jushi, said a vigorous defoliation before harvest means less plant handling later.
“It’s a lot easier to strip off the fan leaves when the plant still has moisture in it,” he added.
A plant can fight off potential contamination from humans touching it when it’s still alive. Once the stem is cut and the plant starts to dry, removing the leaves requires a rougher action that might knock off trichomes.
“We try to minimize the amount of touching as much as possible,” Malman said.
Stripping off fan leaves early so you don’t have to deal with more wet plant material once the colas are cut means less moisture in the dry room, said Rye Matthews, a marijuana and hemp cultivation consultant in Middlebury, Vermont.
“At the end of the year, your biggest battle is with powdery mildew and botrytis,” Matthews said. So, the less moisture, the better.
Higginbotham countered that defoliating the plants really works financially only for grows of a certain size.
“Commercial growers need to work to have the lowest cost per pound,” he said. “To de-leaf the entire canopy would be an extreme cost.”
Flush it, or not
A lot of growers who add nutrients, particularly those that are salt-based, like to flush their plants a few weeks before harvest.
Malman with Jushi won’t run nutrients for the last 10 days or so, only pH-balanced water.
The thinking is that just running water through the cannabis for the end of its life will ensure cleaner, better-tasting flower.
Matthews said flushing is important “to get a clean product out there.”
Devereux’s grow is certified organic, so employees don’t use the type of nutrients that would typically be flushed, such as premixed plant feed.
As another example that flies in the face of more traditional practices: Higginbotham feeds his plants all the way to harvest.
“I’m not going to restrict the plant by not feeding it,” he added. “I haven’t had any negative claims about the smokability of the product.”
Don’t wait until the crop’s cut down before deciding if the drying space will be adequate.
“A lot of growers are unprepared,” Matthews said. “Have that drying space ready ahead of time so, if you have to start harvest a week earlier, you have the ability to do it.
“That’s the difference between having a good year and a bad year.”
He’s seen a lot of growers underestimate how much space they need. Matthews recommends doing a simple test: Hang up a couple of plants and see how much space they take up. Plan accordingly from there.
The other big part of preparing the space for storing harvested material is ensuring the temperature and humidity are controlled.
Kralick sanitizes the dry room – as well as all tools – between harvests to prevent cross-contamination.
“Really silly things can happen if you don’t keep it clean or stay on top of it,” she said. By “really silly,” she means a microbial outbreak.
Kralick keeps the room at around 40%-50% relative humidity and 60-65 degrees, which is on the colder side.
“That gives us a little more of a window to get that plant broken down before it starts to wilt,” she added.
Bart Schaneman can be reached at firstname.lastname@example.org.