Fish Poison Tree
Piscidia mollis
Family: Fabaceae
OTHER COMMON NAMES
Spanish: palo blanco
CHARACTERISTICS
This is a very unusual tree, typically reaching 15-20’ in Tucson but can get over 50’ in frost free zones. Evergreen unless frost damaged or drought stressed. Pinkish flowers in summer followed by interesting winged pods. Rarely planted in Arizona. There used to be a few trees around Tucson but a catastrophic frost took them out some years ago. The tree in the picture is still growing at University of Arizona.
LANDSCAPE USE
This is a specialty tree—an accent reserved for microclimates in our region.
GROWING CONDITIONS
AN EXPLANAITION OF TERMS USED
SUN full sun to part sun
WATER moderate water
SOIL not picky, but well-drained with amendment makes for faster growth
HARDINESS hardy to 20-25°F, some foliar or tip damage in the upper 20s
BASIN middle zone
CONTAINER not recommended
NUTRITION low
MAINTENANCE very little
ECOLOGY
Native along washes, good nesting tree. Nectar-rich flowers. Seed pods are butterfly-shaped, probably to help the seeds disperse with wind.
Photo from the University of Arizona Campus Arboretum
Piscidia mollis on iNaturalist
ETHNOBOTANY
The leaves of this tree have been used by fishermen as a fish poison. The fish reportedly will recover and are safe to eat after ingesting. The wood is also used for fuel and posts.
NATURAL DISTRIBUTION
This plant grows naturally in central and southern Sonora as well as northern Sinaloa. Found in valleys and on gentle slopes in sandy alluvium.
TAXONOMY AND NAME
This species is in the Fabaceae, the legume family. There are 7 species in the genus Piscidia native to the tropical Americas, ranging from northern Mexico and Florida through Central America and the Caribbean to Venezuela and Peru.
Piscidia means fish killer and mollis means gentle or soft.
Foliage detail, photo by J. Fernando Pío León, iNaturalist
Flower detail, photo by Miguel Gastelum, iNaturalist
The dried seed pods, the shape is very unusual for a legume. Photo by Manuel Guillermo Millán Otero, iNaturalist