Death by plant toxins are pretty unpleasant and a bit unreliable. There's a website that rated poisonous plants and their use for suicide, if I find it again I'll throw the link, but overall they're not the greatest methods. Aconite can kill you but only after hours of intense pain. A few months ago I tried to ctb with a mixture of deadly nightshade, mandrake root, and lily of the valley. I was bedridden for three days with extreme abdominal pain and an intense fever, received no medical attention yet I still lived. I'm probably just unlucky but I def would not recommend unless you really hate yourself.