Caesalpinia gilliesii is a member of the Legume Family, Leguminosae or Fabaceae, more commonly called the pea family (or bean, or legume family) because of the structure of its flower and resulting beans or peas that are its fruit.
Its common name is Desert Bird of Paradise or Bird of Paradise Bush because of its vague resemblance to the genus Strelitzia Bird of Paradise, but it is not related.
Its flowers are large, impressive, and colorful, but not useful for cutting. Cutting a branch off just reduces the plant; it won’t grow back there or flower more prolifically as do many other plants.
Flowers have 5 yellow petals with red veins, and long, bright red stamen. The flowers are borne on woody stems, which is part of the reason that they are not great for cut flowers. Cutting off the woody stems does not help the plant and will stunt it over time. Best to leave it to form its own shape unless it’s crowded by something else.
Caesalpinia gilliesii will form an ample shrub of 3 feet – 6 feet tall and equally wide (depending on seasonal rainfall), after only 3-5 years. It will tolerate the punishing heat of the desert with only minimal die-back.
Its abbreviated leaves are a frosted, dusty green. In severe drought, it will cease flowering and drop leaves to reduce demands on the plant and stay alive.
Caesalpinia can also handle temporary low temperatures in the mid 20 degree F range but will freeze to the ground if such cold is maintained for more than several days. Outside of hot, dry environments, it grows slowly and, to some degree, in a stunted form. We are testing this plant in a Mediterranean climate right now (that is, dry summers and rainy winters; moderate temperatures all year round) and see that it is very slow-growing. It really does prefer the heat of the desert!
After flowering, it produces a bean or pea pod of several inches long, covered with soft, short, glandular hairs. The unopened flowers are also covered with glandular hairs, as shown in the picture to the right.
Pods enclose rich, mahogany colored seeds. It sprouts easily from fresh seed; that is, seed that has just been harvested, and grows quickly with ample water. If seeds are allowed to dry out, much more efforts is involved in breaking dormancy, but seeds will normally still sprout, just with a long wait time.
Its bipinnate leaves are 10-15 cm long. They are a good example of a desert plants whose leaves are reduced to a very small size to preserve water by reducing transpiration.
In the wild, it self-sows pretty easily given ample moisture to get the new plants started with sufficient roots before the summer sun sets in.
Once established, it is tough as nails during the hottest and driest season. In desert-like environments, it sometimes self-seeds, a method that has the greatest chance of success.
It is a great desert landscape plant that, once established, will generally survive on its own.
It is not, however, a great plant for poolside locations for two reasons: 1) The pretty red stamen fall off after flowering and are blown into the pool water where they have to be removed; 2) The seed pods “explode” to scatter the seeds, which invariably land some in the pool water where they could clog pool cleaning equipment or the drain. It’s best to plant it away from the pool!
Under the right conditions (ample moisture and temperatures under 110 degrees F), it will flower for months, through the spring, summer, and into the fall.