Red Elderberry - All Questions

They are plain cultivars. Native I cannot tell you, since it depends what state you are in if it is native in your state or not. Most states in the US are native for the America elderberry with the exception of some west coast states.

Important Note: Plant parts and raw, unripened berries are toxic to humans and animals and are especially harmful to children. Only the red, ripened berries should be picked and eaten or processed into other foods.

The leaves and stems of some, if not all, members of this genus are poisonous. The fruit of many species (although no records have been seen for this species) has been known to cause stomach upsets to some people. Any toxin the fruit might contain is liable to be of very low toxicity and is destroyed when the fruit is cooked[65, 76]. NC State University have noted Cyanogenic glycoside and alkaloids can cause low toxity if eaten.