I've been growing them here in zone 4 MN for several years (approx. 12). I started them from seeds.

Thanks, kms4me, are they in the sun or shade? I would love to see a photo of one in the shadiest spot you're growing them in. Have you suffered in hard freezes or in late spring freezes?

Sorry I didn't see your response earlier. I don't have any photos to share, but they are all grown in a lot of shade.

Here is a 5-year-old seed grown plant that gets good light but no direct sun.