Quantifying industrial hemp pollen movement

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Larry Smart, Chris Smart, Rebecca Wilk, and George Stack

Production of cannabinoids drops after pollination

Pollination of fields of female hemp plants is a major concern because cannabidiol (CBD) production drops 2- to 3-fold upon pollination.

Graph showing how CBD production drops when a hemp plant is pollinated.

Industrial hemp is wind-pollinated

Hemp pollen is carried to female flowers by the wind. Long-distance movement (>10 miles) of pollen has been suggested, but there is little published data to support this. Experiments by Small and Antle (2003, J. Indus. Hemp 8:37) with pollen traps indicated there was pollen rain at 400 m, but it was <1% of total pollen rain. They did not survey the actual pollination of female plants.

Graph showing that movement of pollen decreases over longer distances

Pollination distance trial

We planted a ~3 acre field of the monoecious cultivar ‘Anka’ as a pollen source, surrounded by microplots with female plants of three CBD cultivars at 0 m (control), ~200 m, ~400-500 m, and 1,500 m to the east. Male plants and male parts on female plants have been actively removed.

Map of our pollination distance trial pollen source and surrounding microplots.

Cultivars/lines in our 2018 trials

Cultivar/Line Company source Breeder/Provider
Otto II Winterfox Farms, Eagle Point, OR Edgar Winters
Wild Horse Winterfox Farms, Eagle Point, OR Edgar Winters
A2-R4 Winterfox Farms, Eagle Point, OR Edgar Winters

Quantifying pollination and impact on CBD production

We will survey for seed set on each plant and at the end of the season harvest seeds and weigh seed production for each plant. Cannabinoids will be analyzed from flower buds and whole plants for each plant in the microplots to determine the impact of pollination on CBD production.

For results, please see our handout titled, “2018 Cannabinoid production analysis.”

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