Not too long ago, a committe in Switzerland was charged with trying to delineate a reasonable ethics of plant use. The Federal Ethics Committee on Non-Human Gene Technology wrestled with this sticky question since the approval of experiments in genetics and subsequent funding require that the ethical dimensions of the experiment pass muster.
It is interesting that they concluded that bio-technology in the form of gene manipulation or transfer was not necessarily unethical and that any motive which means to conserve the survival of humans is automatically an ethical motive. The one thing they had issue with was eliminating the plant's ability to reproduce or destroying the mechanisms within it by which it might adapt in the future. The notion here I am reasonably sure is that such manipulations would doom the plant to extinction. Hybrid Rose growers wanted to make sure they knew that the most beautiful roses used to convey the highest human expression of affection required that the male plant be sterile. They did not object (in the majority) to private ownership of species, i.e., patents as unethical.
The more bedrock interesting thing about this ethical struggle was first the desire to engage it. That I believe is commendable. The second is the implicit if not explict finding that plants have intrinsic value (value other than that which accrues to them simply for their usefulness or economic value to humans).
If you hold the idea that plants have intrinsic value it does not mean that you cannot harvest them for food, mow your lawn, kill your lawn with herbicides to plant a different species of grass for aesthetic or other reasons. Nor is it a problem to pick the petals from a Daisy one at a time while contemplating some decision.
What it does mean is that it is unethical to treat a plant with intentional disrespect, like wacking the heads off a row of blooming plants just to relish in their destruction, the way some teenagers wack the mailboxes off of their posts late on Friday nights. There is a difference in that vs. spraying them with a herbicide because your new landscaping requires their removal.
The key to understanding the difference is the meaning of the action.
