Answer: Toxic. Most definitely toxic. This is the Castor Bean plant, Ricinus communis. It is often grown as an ornamental, and the decorative seeds, called castor beans, are the most toxic part of the plant.
The toxic principal, ricin, is considered one of the most poisonous naturally occurring substances known. Ricin is found in all parts of the plant, but is concentrated in the beans, which are used in necklaces and other jewelry. If swallowed whole, they may pass out without causing harm, but when broken open (i.e., chewed) just one bean can be fatal to a small or medium sized dog. Children can also be poisoned by eating castor beans.
Signs include oral irritation, burning of the mouth and throat, increase in thirst, vomiting, diarrhea, kidney failure, and convulsions. Death may occur in 36 hours if emergency treatment is not started immediately.
Cornell’s web site says “Never let the plant go to seed,” but my advice would be “Never grow it in the first place.” There are a lot of plants out there that are a lot prettier (in my opinion) without the potential for harm.
Castor Bean plant by KGMom
Single castor bean by MrBrownThumb, Flickr
Bowl of castor beans by Flavio Cruvinel Brandao, Flickr