A new kind of crunch
by Sally Colby
Baby greens have become a consumer favorite, and many growers have added the crop to their lineup. Baby leaf hemp is the latest green to entice both growers and consumers.
Dr. Neil Mattson, Cornell University, said hemp seed and grains are generally recognized as safe by the FDA. However, the USDA-AMS hemp program recently released their final rule for hemp production, and baby hemp is not currently included in the program.
“Baby leaf hemp as an edible salad green is still in a gray area,” said Mattson. “It’s not formally recognized by the USDA in terms of their hemp program … The best advice I have is to check with your state hemp program that’s giving you the state license. They can answer as to whether they will accept it.”
Baby hemp is an edible salad green grown from Cannabis sativa seeds. Some growers use CBD hemp and grow plants to flowering stage then harvest the flowers for seed. Almost all the CBD and THC in the plant occurs at the flowering stage, so if a young, vegetative crop is harvested, Mattson expects to find very low levels of CBD and THC.
Baby leaf greens were introduced to the U.S in the late 1960s as specialty cuisine in restaurants. Mattson said New York growers have been able to sell baby leaf hemp as a high value niche crop to restaurants at up to $30/pound.
“In our baby leaf hemp production, we harvest the plant at the third true leaf stage,” said Mattson. “So you have the cotyledons and the two leaves that have expanded, then initiation of that first true leaf. We find that happens about 13 to 18 days after sowing.” Harvested at this stage, the stems are fibrous but not yet stringy, so it’s an edible leafy green.
“We grow baby leaf hemp in 10-by-20-inch flats with well-drained soil as substrate,” he said, explaining his trial. “We used a potting mix that was blended coconut coir, peat moss and a starter nutrient charge. Seed density in our trial was 1.2 seeds per square centimeter” – 1,550 seeds. Hemp varieties average about 27,000 seeds per pound.
Flats were filled to about two inches with the substrate and seeded on top. “We tried to carefully broadcast the appropriate amount of seeds across the tray, then covered them with another half inch of substrate,” said Mattson. “Temperature was at 70º to 74º Fahrenheit for both the germination stage and growing. Germination to emergence from the soil was two to four days.”
Baby hemp was subject to damping off (Pythium and Phytophthora), so Mattson cautioned growers to be aware of overwatering to the point of saturating the substrate. Plants were fertilized with Jack’s 21-5-20, an all-purpose liquid feed at 150 ppm nitrogen. Sub-irrigation was used to avoid wetting the foliage. Mattson said the concern was that with such a tight canopy, the leaves stay wet for too long, making them more sensitive to botrytis gray mold.
The crop was harvested at the third true leaf, about 13 to 18 days after sowing, by cutting just above the soil line at the cotyledon. “We used the top of the plant,” he said, “which is about three-quarters or seven-eighths of the shoot.”
When Mattson first started working with hemp, it wasn’t clear which cultivars would be most suitable. He worked with university personnel, conducting field hemp research using fiber, grain or dual-purpose varieties. “Based on some of the field studies being done at Cornell, we selected several dual-purpose cultivars and grain cultivars,” he said. “The cost of the seeds, because these are field hemp cultivars, ranged from $2.65/pound for Anka to $10/pound for Canda and Joey.”
Nine cultivars were selected for the trial, including Anka, USO-31, Ferimon, Wojko, Katani, Picolo, X-59, Canda and Joey. Mattson noticed that germination percentage during the trial varied by cultivar. “Picolo and X-59 had the best germination at 75% to 80%,” he said. “Poorer germinating varieties were Wojko and Joey.” The poorer germination may have been due to the specific lot and not the cultivar. Mattson suggested checking with the seed supplier for germination rates, or growers can conduct their own small scale germination testing.
Cultivar performance varied in terms of fresh weight (ounces of harvested shoots per flat). The highest performers were Picolo and X-59, which yielded about 6.5 ounces/flat. Katani, Ferimon and USO-31 also performed well. Mattson said the poorest performing varieties were Wojko and Joey, which also had the lowest germination rates.
Using 1,801 cell trays, Mattson tested five sowing densities, from 840 seeds to 3,675 seeds/flat, using Ferimon and Katani in the trials. He found no significant effect of sowing density on germination percentage or plant height. He also looked at sowing density related to harvest yield/flat. “As sowing density increased, we saw an increase in harvested fresh weight,” he said. “There was also higher damping off and disease pressure at the maximum sowing density.”
Seed size proved to be a notable factor in plant performance. “If you buy baby leaf greens from a seed company, they’ve selected and sorted by quality,” said Mattson. “With baby hemp, there isn’t that kind of seed quality by size treatment so you get bulk seed lots for field production. We took several seed lots from three different cultivars (Anka, Ferimon and Picolo) and ran them through the sieves to determine the number of seeds in each size class.” The finding that was larger seeds resulted in better fresh yield.
The recommended cultural practice from Cornell is to use seed lots that have good germination (like Picolo and X-59). There was a notable benefit to increasing sowing density to 3,000 seeds/flat, which is about 50 grams (1.75 ounces) of seed.
They recommend a warm room temperature of 70º – 74º, and if you’re a conventional grower, a water-soluble fertilizer at 200 ppm nitrogen is best. For organic growers, Sustane 8-4-4 at eight pounds/cubic yard worked best, Mattson said.
With good yields in summer and optimized conditions, the yield was about eight ounces of harvested product/flat. When parameters were compromised, yields were lower.
Part of the trial involved consumer sensory evaluation, so Mattson worked with the food science department at Cornell to determine taste perception and comparison to other baby leaf greens. Baby leaf hemp was compared to baby kale, romaine lettuce, butter lettuce, spinach and arugula. Evaluations were based on aspects such as flavor, appearance, aftertaste and texture. “For texture, hairy was one of the textures that came up – baby hemp has a peach fuzz hairy texture,” Mattson said.
Consumers tasted each of the six baby leaf greens and rated appearance, flavor and texture. The hemp cultivars have distinctly different flavors compared to baby spinach, romaine lettuce and butter lettuce, and those were distinct from the flavors of baby kale and arugula.
“Arugula and kale had a more spicy and bitter flavor than baby hemp and a little sharper than baby romaine, spinach or butter lettuce,” said Mattson. “We didn’t ask if testers preferred hemp over the other greens. But based on comparisons with other greens, there are some positive and negative aspects of hemp.”
Although he hasn’t determined a price point or margin per flat, Mattson said the economics stack up pretty well, and it’s reasonable to think baby hemp would be competitive. And while baby hemp doesn’t yield as well as some microgreens, Mattson believes that if there’s a market, there’s money to be made.