I love contrasting colors ... so I would have to say
Favorite flower - Blazing
Favorite plant - Rare Oak
so Blazing Rare Oak

But it was a tie with
Mystic Fern because two of my favorite colors are green and purple and I like the feathery leaves.

Least favorite? Bamboo for plant, and venomous for flower (I can't see those small black dots on many of the plants!!!)