Butterfly Weed, though very pretty don't have the most romantic, or even postive meaning. Butterfly Weed menas "Let me go", meaning, if you don't plan to break up with your partner, aviod giving them these flowers.
Wallflower is a beautiful orange flower with an equally beautiful meaning. Wallflowers are linked to the phrase "Faithfulness in adversity" which meanings being together even in the face of difficulties.
The Zinnia flower is another gorgeous orange flower but it doesn't make for the best gift. Zinnia flowers mean "Thoughts of absent friends" which means they could be a nice gift to give an old friend.