Q.Can An Unpatented Plant Be “exclusively Licensed” To One Grower, And Prohibited Propagation To Everyone Else?
I’m fairly confident in my understanding of patents, but licenses are not something I know a whole lot about yet. If there is an imported plant that is unpatented, but the grower claims it has “exclusive” license and rights to propagate in the USA, and propagation is strictly prohibited to anyone else, how much legal ground do they have to stand on?

Certified GKH Gardening Expert
The way I understand it, only the owner of a patented plant would have the right to license it to others to grow. Who would he get the "exclusive license" from if no one owns a patent on the plant? You may need to consult a lawyer, though, if you need a definitive answer.
https://ucanr.edu/sites/Shasta_College_Master_Gardener/files/242899.pdf
https://www.gardeningknowhow.com/garden-how-to/propagation/propgen/plant-patents-and-propagation.htm
https://itc.ucdavis.edu/plant_varieties_licensing_program/#licensing