Etiquette of posting plants from botanical gardens?

Consider obscuring a rare plant’s location to decrease the likelihood of its getting stolen or clipped. See the discussion Best way to obscure.

With some detective work, a motivated person may find the plant anyway, but if that person feels about the plant as we hope most iNat people do, myself included, the result will be a visit to the plant only to admire it, with the plant remaining unharmed as of the conclusion of the visit. ;)