It's a novel invention and no one needs glowing petunias. I think that's pretty much the ideal scenario for a patent.
Also, exerting control over a commercial cloning effort and trying to control personal use and propagation are totally different scenarios.
The reality is their business is just not going to be substantially hurt by personal propagation and use.
Practically? Unless you gift it to a thousand "friends", they're unlikely to a) hear of it, b) care about it, or c) break even on the legal costs of going after it.
We have the USDA for these things. https://www.aphis.usda.gov/news/program-update/aphis-issues-...
> APHIS found this modified petunia is unlikely to pose an increased plant pest risk compared to other cultivated petunia. As a result, it is not subject to regulation under 7 CFR part 340. From a plant pest risk perspective, this petunia may be safely grown and bred in the United States.
No one's putting in decades of R&D into something like this if they can only sell a few thousand for a single year before the big nurseries take over.