Spiny Senna
Senna armata
Observed at Joshua Tree National Monument, California. 30 April 2010.
RANGE: This is really a Mojave Desert plant that is found occasionally
at the ecotones where it meets the Sonoran Desert. California and far western
Arizona.
SHRUB: Most shrubs are about 1½ m
tall.
FLOWERS: Bright waxy yellow, sometimes with red tinge and with five
petals. Unopened buds are shiny and arrayed in spikes at branch ends.
ARMED: Twiglets are sharp at the tips and one or two years worth of
dead, spiny twigs remain on the plants adding more armour.
LEAVES: The compound leaflets are few (2 to 8) and are soon shed with
drought leaving the leaf rachis to carry on photosynthesis.
FRUIT: Straight pod, about 4 cm.
long and with a few beans.