Received an offer for 6-8 small "trees". I accepted but when I checked them out, two of them were Sumac(fruit cones on tips). Since there were no leaves and snow on ground so couldn't see any leave signs at all, How would I be able to tell if it was poison Sumac? I'm not interested in it for heating since I learned that Sumac is pretty lame in the BTU department. In fact I threw it over the bank. But for knowledge purposes I'd like to know how to identify if no leaves are available. When cut the sap did turn blackish but from what I read there is also another species that will do the same thing. Any tell tale signs to know it's poison without leaves? I am pretty sure it was OK because it was not a wet area but not willing to take the chance for a low BTU output. On a positive note, the other 5 trees were small cherry trees(I'll be confirming this with pictures in a few days) so it was not a waste of time.