I have three senna bushes, and they bloom in early spring, meaning the end of January through February. Now at the beginning of March, they are setting seeds.
This is my narrow-leafed senna. I don’t have a good idea about the species names for these, because the web pictures aren’t as good as I’d like to identify them. Anyway…
This one has yellow flowers and very narrow, silvery-green leaves. They flower profusely, and have a sweet, slightly astringent smell.
Being the only thing around flowering, they’re very popular with the bees.
This is Senna #2:
This senna has longer, broader leaves, and appears more green (rather than silvery). The flowers are slightly (very slightly) more orange-y, and the centers are more noticeably brown.
Sennas are leguminous, producing seeds in a bean-like pod. The tiny green curl inside each flower becomes the seed pod.
Senna #3 is a “volunteer”:
This plant is a daughter of the narrow-leafed senna.
There are two senna species native to Arizona: Senna covesii (also Cassia covesii, Desert Senna or Coves’ Cassia), and Senna wislizeni (also Cassia wislizeni or Shrubby Senna). Both of those have much broader leaves than either of my specimens. In addition, my erstwhile (and unmentionable) landscape guy said that my sennas were non-native species and I should be careful not to let them propagate. I think my species are Australian, from a climate similar to the Sonoran Desert.
Each year, the sennas have thousands of flowers, and it seems most of them get fertilized (yay, bees!), so I spend a day every June pulling off seed pods so that the sennas don’t run wild over the local native flora. Obviously, I missed one. This volunteer is at least 35 yards away (and a bit downhill) from the parent plant. It also gets sunlight earlier than the other two, so it blooms earlier.
And the seed pods are already starting to fill out…