Gyrocarpus americanus (Propellerbaum)

Gyrocarpus americanus, commonly known as Stinkwood, Helicopter Tree, or Whirly Whirly Tree, is a deciduous tree in the Hernandiaceae family, widely distributed through tropical regions of the Americas, Africa, Asia, and Australia. It develops a spreading crown with large, soft, broadly heart-shaped to shallowly lobed leaves. The foliage is not noticeably unpleasant under normal conditions, but the leaves release a strong disagreeable odor when rubbed or crushed; the small greenish flowers may also have a slight unpleasant smell. The flowers are followed by distinctive dry fruits, each bearing two long narrow wings. As the fruits fall, the wings make them rotate or spin like small propellers, inspiring the names Helicopter Tree and Whirly Whirly Tree. Young plants can develop an attractive swollen, sculptural trunk base and are sometimes cultivated as unusual bonsai specimens.

Gyrocarpus americanus grows best in full sun and warm conditions with well-drained soil. It is naturally associated with seasonally dry tropical habitats and becomes drought tolerant once established, often shedding its leaves during prolonged dry periods. Regular watering promotes faster growth in young container plants, but excessive moisture should be avoided. Its unusual trunk, broad foliage, and spinning winged fruits make it an interesting collector's plant as well as a landscape tree where space permits. It is best suited outdoors to USDA Zones 10-11 and should be protected from frost.