Flor de San Jose
Senna atomaria
Family: Fabaceae
OTHER NAMES
tree senna
Spanish: palo zorillo, alcaparro, chile perro, hediondillo, viche
CHARACTERISTICS
Mostly evergreen (drought deciduous in the wind) upright tree, reaching 60+’ in its native Mexico, but mostly a 20+’ plant tree here. Yellow popcorn-shaped flowers can occur almost any time of year, often very heavy in spring before leaves come back, followed by legume pods. Because trees in cultivation are usually irrigated, they are often evergreen under such conditions.
LANDSCAPE USE
Specimen shade tree.
GROWING CONDITIONS
AN EXPLANAITION OF TERMS USED
SUN full to part sun
WATER moderate to low
SOIL not picky, but well-drained
HARDINESS hardy into the mid 20s°F, but may show leaf and twig damage; recovers quickly from damage
BASIN high zone
CONTAINER does moderately well in containers but will not attain full size
NUTRITION low
MAINTENANCE very little
ECOLOGY
Flowers are nectar rich and visited by many butterflies, bees, and more. Butterfly larval plant for the Boisduval's Yellow Abaeis (boisduvaliana), Sleepy Orange (Abaeis nicippe), Cloudless Sulphur (Phoebis sennae), Orange-barred Sulphur (Phoebis philea), Tailed Sulphur (Phoebis neocypris)and moth larval plant for the Genista Caterpillar (Uresiphita reversalis), Salt Marsh Moth or Acrea Moth (Estigmene acrea), and the Black-tipped Rudenia Moth (Rudenia leguminana).
ETHNOBOTANY
It is used as animal food and a medicine and for fuel and food. The genus is famous for being used as laxatives and many species are used as such.
NATURAL DISTRIBUTION
From Sonora, Mexico south to Venezuela.
TAXONOMY AND NAME
This plant is in the Fabaceae, the legume family. There are 272 species of Senna.
This plant was formerly known as Cassia emarginata.
The genus name derives from the Arabic sanā, describing plants whose leaves and pods have cathartic and laxative properties. The species name “atomaria” means atomic—could be referring to the many minute dots on the leaves?
This tree naturally grows in the sierras in Mexico, amongst other trees and arborescent cacti. Photo by Enrique Flores García, iNaturalist
In the dry spring plants are often leafless and bloom just before the rains (maybe timing seed release during the monsoon season). Photo by GeRa_MaChaDo, iNaturalist
The seed pods are long and skinny, photo by Consulturismo A.C., iNaturalist
These trees are very upright growing. Photo by conabio-pj010, iNaturalist