Originally published 2020-01-27.
Yes, bees visit hemp. Two US studies found that bees collect pollen from industrial hemp (Cannabis sativa) in large numbers, especially in late summer when few other plants are flowering. A Cornell University team also found that taller hemp plants attract more bees and a wider range of species. That makes hemp a potentially useful extra food source for bees, but it does not mean hemp on its own can rescue declining bee populations.
Here is what the research actually measured, why bees bother with a plant that offers no nectar, and what it would take for hemp farming to be good news for pollinators rather than a new risk.
The Colorado State study: bees in late-summer hemp
The first evidence came from Colorado State University. Entomology student Colton O’Brien and his adviser Arathi Seshadri set traps in two experimental hemp plots near Fort Collins over a month in August 2016. They presented early results at the Entomology 2018 meeting in Vancouver, and the work was later published in the journal Biomass and Bioenergy.
They caught bees from 23 different genera, out of the 66 bee genera known in Colorado. Visitors ranged from big bumblebees to tiny metallic-green sweat bees, as well as honeybees. As O’Brien told Science News, “You walk through fields and you hear buzzing everywhere.”
Older articles described this as traps placed on large farms across the state; in fact it was a small survey in two research plots. That does not make the finding less interesting, but it is a reason to treat it as a first look rather than a final answer.
The Cornell study: taller plants, more bees
The second study, from Cornell University, was published online in December 2019 in Environmental Entomology. Nathaniel Ryan Flicker, Katja Poveda and Heather Grab used sweep nets to collect bees visiting hemp flowers on farms across New York State, then identified every bee to species.
Their main findings:
- 16 bee species were recorded on hemp.
- Plant height mattered most. Taller hemp varieties drew both more bees and more kinds of bees.
- Landscape mattered too. Farms surrounded by simplified landscapes, with less natural habitat, had fewer bees visiting their hemp, although the number of species stayed similar.
- Timing is a plus. Hemp flowers during a period of floral scarcity, so it may provide food when bees struggle to find it.
The two studies support each other: Colorado showed that many kinds of bees use hemp, and Cornell added the link with plant height and surrounding habitat.
Why bees visit a plant with no nectar
Hemp is wind-pollinated. Its flowers produce no nectar, the sugary liquid that fuels adult bees, so it does not need insects to reproduce. What male hemp flowers do produce is a lot of pollen, and pollen is the protein source bees feed to their larvae.
In late summer, after many crops and wildflowers have finished blooming, a field of pollen-rich hemp can be one of the few options around. That is why researchers describe it as a possible “bridge” resource during the seasonal dearth. One open question is nutrition: scientists still know little about how good hemp pollen is for developing bees compared with pollen from a mix of flowers.
There is also a practical catch. Much hemp grown for CBD is planted as female-only crops, because pollinated female plants produce fewer cannabinoids. Those fields have little pollen to offer. The bee-friendly picture applies mostly to hemp grown for fibre and seed, where male plants are present.
Why bees matter so much to food production
Bees are among the most important pollinators of crops. When they move pollen from the male parts of a flower to the female parts, they allow many fruits, nuts and seeds to form.
The UN Food and Agriculture Organization, citing a 2016 global assessment, put the annual value of crops directly affected by pollinators at between $235 billion and $577 billion. In the United States, the American Beekeeping Federation estimates that honeybees contribute around $20 billion to crop production each year. Almonds, blueberries, cherries, apples and many melons rely heavily on bee pollination.
Many wild bee species have declined because of habitat loss, pesticides, disease and parasites such as the varroa mite, and climate change. Managed honeybee colonies in the US have also suffered high yearly losses. So any crop that provides extra food is of interest.
The pesticide question
The same researchers raised a warning. Hemp farming in the US expanded quickly after the 2018 Farm Bill made industrial hemp legal to grow, and pest management for the crop was still being worked out. If growers start spraying insecticides on fields full of foraging bees, a food source could turn into a hazard.
The Cornell authors urged growers, land managers and policymakers to take hemp’s attractiveness to bees into account when designing pest control. In practice that means choosing bee-safe products where possible, spraying when bees are not foraging, and monitoring pests before reaching for chemicals.
Common myths about hemp and bees
- “Hemp will save the bees.” No single crop can do that. The studies show bees use hemp, not that hemp reverses population declines. Diverse wildflowers, hedgerows and reduced pesticide use remain the core of pollinator conservation.
- “Bees get high on cannabis.” There is no evidence of this. Industrial hemp is bred to contain very little THC, and bees collect the pollen as food.
- “Hemp honey is a thing.” Because hemp has no nectar, bees cannot make honey from it. Products sold as “hemp honey” are usually ordinary honey with hemp extract added.
What it means for farmers and gardeners
For farmers already growing hemp for fibre or seed, the research suggests a bonus: their fields may support local bees during a lean season, especially with taller varieties and some natural habitat nearby. For everyone else, the wider lesson is the one bee scientists keep repeating. Bees need flowers from early spring to late autumn, safe nesting places and fewer toxic sprays. Hemp can be one piece of that puzzle, alongside the clover, wildflowers and fruit trees that bees have relied on for much longer.
Sources: Flicker, Poveda and Grab, Environmental Entomology (2019); Science News: Hemp fields offer a late-season pollen source for stressed bees; O’Brien and Arathi, Biomass and Bioenergy (2019); FAO; American Beekeeping Federation.
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