Food safety
Can dogs eat rhubarb leaves?
No — don't give this
The leaves are toxic. Worth knowing if you grow it in the garden.
Being honest about this
Dogs differ, and amount matters — a crumb of something rich is not the same as half a packet. Treats of any kind should stay under a tenth of what your dog eats in a day. If you're unsure, your vet would far rather take the call.