This small tree-like perennial from Jamaica and South America is sure to invoke curiosity. It's in the Milkweed family, and grows 4-6 ft tall. The flowers are white and inverted, like many milkweeds. It is the seed pods that are showy. They are balloon-like, translucent lime green, and have little spines sticking out. The seed case of this fantastic plant looks just like a swan, which gives it its other common name. Like all milkweeds they attract the lovely wanderer butterfly to the garden. The downside is that the seeds spread very easily throughout the garden on the breeze, so the plant does have some weed potential. Another problem is that it exudes a poisonous, milky sap. However it tastes bad and is not really the sort of thing you'd want to eat.