I think you have to get the license before you take cuttings or do air layering. Here is what the Oregon State University Extension Service says -
"A patent legally prevents others from reproducing the protected plant variety by cuttings, tissue culture or any other method of asexual propagation without the written authorization or licensing of the patent holder. Possession of improperly propagated plants of patented varieties constitutes infringement, even if an illegal propagation was inadvertent.
Though asexual reproduction may be prohibited on a patented cultivar, there is no regulation against using the plant in sexual reproduction. In other words, the seed or pollen from a patented variety may be used without permission of the patent holder. The offspring are free of patent regulations.
To determine if a plant is patented, look for a patent number on the tag, or PPAF (plant patent applied for) or PVR (plant variety rights) after the name of the cultivar. Or sometimes there are other indicators that a patent has been applied for, such as “patent pending.”
If a plant is patented, a license is required from the patent holder in order to make cuttings of that plant, even if it is planted in your own back yard. Unlike with a copyright, there is no concept of “fair use rights” for patents in the United States."
