I assume you are thinking of poison (aconite) being left in the compost, since Aconitum has the reputation of being one of the more toxic garden plants. I have had several different kinds in my perennial beds for 20 years or so & have always composted it. I have never experienced any problems. I handled it & clipped it without gloves or any precautions till the last few years, but now I take more care, on general principles.
