Butterfly Bush - All Questions

Yes, once established, Butterfly Bush is drought tolerant. During the first year, however, we recommend regular watering in the event you aren't receiving about 1" precipitation per week.

Depending on what you want to achieve in your landscape, you can space anywhere between 3-10' apart. If you are making a hedge you could space about 3-4' apart.

Indeed, Butterfly Bush is hardy in Zone 4. We suggest mulch for all trees and shrubs. Just be sure to keep it away from the stem.

Native is a term that depends regionally, is it native to where you are located? Since I do not have your location, I cannot answer that question. Butterfly bush is invasive in many states, you should check your local resources to see if it is invasive in your state and if it is I would suggest not ordering it. Many states in the northern areas it is not considered invasive. You could also plant instead some of the following butterfly bush varieties considered sterile.
Lo and Behold Series Butterfly Bushes (Sterile)

Blue Chip Butterfly Bush

Blue Chip Jr Butterfly Bush

Ice Chip Butterfly Bush

Lilac Chip Butterfly Bush

Pink Micro Butterfly Bush

Purple Haze Butterfly Bush
Miss Series Butterfly Bushes (Sterile)

Miss Molly Butterfly Bush

Miss Pearl Butterfly Bush

Miss Ruby Butterfly Bush

Miss Violet Butterfly Bush