An overview of the sea of green method: A tradeoff between size and speed
By Karli Petrovic
From tulips to tomatoes, the Dutch have it figured out. As one of the top producers of agricultural products, it’s no wonder the rest of the world looks to the Netherlands for growing tips and methodologies. It’s fitting that the Dutch also have a namesake cannabis production method.
The Dutch method — also commonly referred to as sea of green or the 12-12 method — is a particular style of indoor growing that essentially skips the veg stage. Once established, clones are immediately introduced to 12 hours of light followed by 12 hours of darkness. This process triggers the photoperiod, which tricks into flowering early.
The result is smaller plants (typically 12-24 inches with one large bud), reduced electricity costs and quicker crop cycles. While the method isn’t ideal for most commercial growers, it can be beneficial for some growers where timeliness and space are concerns.
“I do think it is a viable method, as it cuts the time it takes to harvest,” said Kelly Hansen, a horticulture scientist with experience growing cannabis. “A typical strain takes about 65 days in flower to harvest. Seed propagation to establishment takes about a month, and then depending on how large a plant you want, vegetation time is added.”
Hansen said the Dutch method is helpful for growers who want to quickly identify strains, phenotypes and plants that produce the best quality.
“When you start with seeds, you want to keep that genetic line viable,” Hansen said. “Growers test the quality by propagating from that seed, flowering it out and harvesting the flowers. Then they can directly correlate which mother seed the plant came from.
“It is important to weed out the weak phenotypes in your garden. A desired trait is usually obtained, and the other seed plants that did not have the said trait will be flowered out or discarded,” she said. “The Dutch method seems to be of great value in situations where someone has invested money into seeds, and needs to keep a mother plant for future cycles. Having a quick turnaround time to evaluate the traits per individual seed plant alleviates the dreaded, long process of mother selecting.”
This is especially beneficial to growers looking for the right strain for their operation, said Clinton Zuber of Zoobees Doobees, a licensed marijuana grow operation in Spokane, Washington.
“The pros of the sea of green method are that certain strains respond well; the cons are that some strains do not respond well,” Zuber said. “With the shortened time period, I’m always able to flower out a room per month.”
For those like Zuber who deal with space constraints, the Dutch method can be ideal.
“With the Dutch method, the plants’ size and canopy all grow evenly,” said Timothy Anderson, purchasing manager for Harborside Health Center, a medical cannabis dispensary in California. “The canopy fills up perfectly so that there isn’t any dead space.”
Combined with the quick turnaround rate, the Dutch method makes cleanup between cycles seamless.
“By using small plants, it’s easy to move them in and out of the room quicker,” Anderson said. “There’s less biological mess and fewer soil-borne pests. The equipment is also easier to clean, as you can sweep out the room, sanitize the entire thing and start fresh each time.”
Trimming smaller plants takes less time, and faster flowering can help reduce energy consumption.
The smaller, faster-flowering plants can be more time-consuming when seed-to-sale tracking is required. Registering the plants with individual bar codes for seed-to-sale tracking systems can be a hassle, Zuber said. Because growers need to maximize their potential profits, it’s more efficient for most to produce larger plants with multiple buds.
“In California, where so much of the law is based on plant numbers, it doesn’t make sense to develop this method as a form of farming,” said Chris Van Hook, attorney for Clean Green Certified, a third-party cannabis certification program. “It may be more time efficient, but it never caught on because of the high plant numbers.”
Growers ultimately have to do the math on whether the Dutch method makes sense for their operation, either as a primary technique or to supplement more traditional light schedules for breeding.
“As greenhouse technology continues to advance, sea of green and other indoor farming methods will probably be appropriate in fewer and fewer spaces,” Van Hook said, noting that he hasn’t seen a university study that proves the method is the most efficient use of space.
Similarly, he estimated the sea of green method yields less than an ounce of cannabis per plant. Compared to those grown in three-gallon pots that might yield two to four ounces each, or five-gallon pots that yield four to eight ounces each, growers could conceivably produce more cannabis with taller plants.
As with other methods of cannabis production, there’s wild variation between the inputs, equipment and controls that are used. There are almost as many different techniques and methods as there are growers.
No matter what style the grower chooses, Zuber said it’s impossible to discern how a bud was grown based on the final product. As Anderson put it, “We don’t differentiate on our shelves.”
However, Van Hook’s philosophy is to do what works for each unique operation.
“No form of agriculture is the best for every location,” he said, noting that a Google search of “best method of cannabis growing” brings up pictures of everything under the sun.
“There is no best way of doing something everywhere.”