No one owns a plant on public land.... wtf.
I have ladies growing 'in the woods'.... they're mine... I grew them from seed, transplanted them and visit them periodically to feed and nurture them. They're mine and fuck you very much.
In most common cases, possession is 9/10ths of the law. Leaving possessions in public places is not ideal, doing it to avoid legal ramifications/risks of growing at home/on property would be logical, but result in consequences (less security). In reality, the seed has and will grow without you "feeding and nuturing" them with your magical human hands (lol), it will be here long after you behead 10 peoples kids for stealing your weed, or whatever internet bravehearts would imply would be the consequences of touching a seed thats grown on public land. That worked during founding of USA (genocide of natives) but in modern days, killing or shooting someone over a plant would be quite hilarious news story for mere entertainment factor really, nothing more then a sensational news story.
Realistically, the lack of security falls on the grower for using public land, or planting in a traveled area. A thief will always be a thief, not that I really consider someone taking a bud from a plant in public stealing, as I mentioned possession laws. I don't personally know anyone stupid enough to grow in public and expect security, or is willing to kill over the plant, but they seem to be in bunches on internet forums.
Reminds me of kids with "stop snitching" t-shirts diving behind stuff with their iphones dialing 911 when gunshots go off, rofl. I have lack of sympathy anyway though, so its probably just my personal perspective.