I just returned from Tucson, Ariz., where I saw desert birds of paradise in peak bloom. Desert birds of paradise are leguminous woody plants that only need to be watered occasionally and do not require fertilization. They have a light and airy growth habit, the entire plant suggesting flight.
Their leaves are bipinnate, meaning double-feathered (pinna means feather in Latin), resembling those of a jacaranda and certain ferns. I have seen all types grow well in the Valley. You can plant the yellow bird of paradise (Caesalpinia gillesii) with vivid golden yellow petals and red stamens, the evergreen lemon yellow Mexican bird of paradise (Caesalpinia mexicana) or pride of Barbados (Caesalpinia pulcherrima), with its flaming reddish-orange plumed flowers. All reach a height of 10 feet.
Requiring a bit more water than the desert birds of paradise is the more familiar South African bird of paradise (Strelitzia reginae), a relative of the banana. It is also flowering now, showing off clusters of silky orange plumes interrupted by a blue feather or two. Although this bird of paradise is all around us and has long been recognized as the official flower of the city of Los Angeles, if you grew up in the Midwest, as I did, you will forever consider it to be an outlandish and exotic rare bird. In Chicago and Detroit, this locally ubiquitous flower is regarded as a true luxury item, the Rolls-Royce of flora.
This South African bird of paradise, with its paddle-shaped foliage, has a highly desirable, if somewhat frustrating quality: the more crowded it gets, the more it flowers. It develops from rhizomes, bulblike underground structures that cause it to clump and expand in girth from year to year.
However, you do not want to interrupt this expansion. In other words, if a bird of paradise is growing in a terra cotta pot, you do not want to move it until just before it breaks the pot and then, reluctantly, you should transplant it to another pot that is only slightly larger than the first.
Just don’t split the plant into smaller pieces. Bird of paradise dreads being divided and will stop flowering for years as a result of bifurcation.
It shares this characteristic with cymbidium orchids, African violets and many flowering cactuses. Of course, you can still divide your mature plants as long as you have the patience to wait until the divisions develop into flowering clumps of their own.
A subtle truth about bird of paradise is its response to an added measure of warmth. It is a subtropical plant that blooms in winter, as long as the winter is mild, Los Angeles style. Therefore, it will flower that much more if it is given protection from the cold. Bird of paradise flowers most spectacularly when night temperatures are kept under control. A significant amount of heat is gained and retained at night by planting next to a heated building, against a sun-splashed block wall or under a patio roof.
Perhaps the key to growing bird of paradise is an understanding of its ecology. Winter-blooming plants native to Mediterranean climates, such as South Africa’s and our own, require dry summers to flower at full capacity.
If you have birds of paradise that do not bloom much, even though they look healthy enough, the problem is probably excessive watering during the summer. Alternatively, they may be lacking in fertilizer, which they crave on a continual basis.