It is hardy to Zone 4. A surprise plant is any plant the unusual size, color, shape, fragrance, or rarity of which brings you up short. Size and color surprises are the most common in gardens, since unlike rarity alone, they do not depend for their shock value on the horticultural sophistication of one's visitors. A plant in an unusual spot may act as a surprise, too, such as a bell pepper in a hanging basket on the patio. So may a plant the growth of which is accelerated, slowed, or otherwise meddled with for decorative effect.
All topiaries are surprises, usually unwelcome ones.
A mess plant is a plant that refuses to assume any one shape for long. It treads on things around it, sticks you in the eye whenever you walk by, stains the hood of your champagne-colored Porsche with its dropped fruits, litters the garden with its fluff for weeks on end, or leaves huge gaps in the border when it dies back. Indeterminate tomato plants fall into this category. So do most roses, and all oriental poppies. So do cottonwoods.