Scorpio: the yew tree. Magical, mystical, and a little scary. Yew trees are poisonous, and you better bet Scorpio knows how to use it.
Sagittarius: the maple tree. Big, bold, likes to be seen. Seeds travel quickly. Literally cannot avoid them.
Capricorn: the bristlecone pine tree. Lives in some of the crappiest environments, yet still thrives. Does not shed leaves. Will not change.
Aquarius: the birch tree. Doesn't just like to be special, they *know* it. A little stormy weather and they start losing it. Likes to hang out with...themselves.