I've been growing Agastache foeniculum this summer. I also have Agastache rugosa (from East Asia) and our local native Agastache urticifolia. I cannot tell the botanical or taste difference between A. foeniculum and A. rugosa. Both are very sweet and both flower in late summer.
Let me know if you figure it out. I grow rugosa and foeniculum and I "think" foeniculum has a little more fennel taste and rugosa leans a little toward mint. But I'm not sure. Haven't thought about sweetness. I'll pay attention next time I organolepticize them.
I'm really struggling with it! Which makes me wonder about the identity of BOTH of these species. Now looking at the ORIGIN of the A. rugosa seed I bought years ago. Hmm. 🤔
The native Agastache urticifolia flowers are a lighter pink and is not sweet-tasting at all. It flowers in July.
