I love sumac!! Are yours in the photos really the staghorn variety? There are SO MANY variations, I could never be a botanist. The flaming red leaves in autumn are gorgeous. We have a colony of "volunteer" sumac (thank you, birds) that I've watched from seedling to taller than me, and they create a little forest at the edge of our treeline. Toxic, invasive, but native, I love 'em! And I love your facts that accompany your photos. --Wait, you say yours are nontoxic. And here I believed ours (which look identical to your photos) are not. I'd better revisit those botany books! In my childhood we had two staghorn trees with thick trunks that were climb-able, and these look different to me. Maybe it takes many years to reach that stage of being climbable...? Great photos!!