Among the most colorful woody plants growing in Westwood are the species of family Bignoniaceae, the bignons. Most Westwood residents are already familiar with a few bignons, especially the widely planted South American jacaranda (Jacaranda mimosifolia), a deciduous tree that has blue-lavender, funnel-shaped flowers. Also very commonly planted is the South African cape honeysuckle (Tecomaria capensis), an evergreen shrub or climber with curved, tubular flowers of red-orange or yellow--favorites of hummingbirds. Certainly, every Southern California neighborhood should have one or more bignons, growing in spots that receive full sun.
Comprising about 800 species (more than 110 genera), this plant family is a truly remarkable lineage of trees, shrubs, and woody vines (lianas) with large, brightly colored flowers and unusual fruits. Bignons have either opposite or whorled leaves; or, in some cases, both types occur on a single branch. In most species, leaves are once-compound (pinnate, palmate, or trifoliate). A few species possess twice-pinnately compound leaves, and several genera have simple leaves, such as the large, heart-shaped or broadly ovate leaves of Catalpa and the very narrow leaves of desert willow (Chilopsis linearis). In the flower, the petals are fused to form a tubular corolla with five uneven lobes, sometimes giving the appearance of a lower and an upper lip. Copious nectar that collects around the ovary (at the base of the petals) rewards animal pollinators, and, typically, four fertile stamens (occasionally five or two) are fused to the lower half of the corolla. The ovary bears two chambers and matures as a wooden "pod" (in botanical terms, a capsule) with a partition (septum) down the middle. The two wooden valves of the fruit eventually fall off, revealing very flat seeds with prominent silky or papery (membranous) wings.
The following paragraphs highlight some of the species that can be observed in and around Westwood.
Trees
Jacaranda mimosifolia has exceptional twice-pinnately compound leaves, with hundreds of tiny leaflets resembling the dissected leaf of a fern. During springtime, numerous clusters (inflorescences) of blue-lavender flowers decorate the tree. At UCLA, jacaranda can be seen in the Franklin D. Murphy Sculpture Garden and in front of Murphy Hall. During late summer you may observe its flat, circular, wooden fruit, which splits from the bottom upward to release light brown, winged seeds. Growing in Westwood, at the corner of Montana and Veteran, is a white-flowered form of this species. MEMBG has several additional species of Jacaranda in its collection.
For a prizewinning flower in early spring, you should visit the UCLA Court of Sciences, where MEMBG staff have planted a pair of Tabebuia chrysotricha trees. This species is native to seasonally dry tropical forests. Each spring its huge clusters of pure yellow flowers form on bare branches before the palmately compound leaves expand. During late summer, the long, fuzzy brown capsules release their seeds, which often germinate and form seedlings around the mother plants. Other species of Tabebuia, collectively called the trumpet trees, that have been planted around campus and in the botanical garden include the pink-flowered T. impetiginosa (look for these around Kerckhoff Hall), T. avellanedae, and T. hypoleuca. In the rain forests of Latin America, large Tabebuia trees often are important members of the canopy and are lumbered for their interesting wood (ipe or amapa).
Equally stunning are the red and orange, bowl-like, fist-sized flowers of Spathodea campanulata, the African tulip tree or fountain tree. One of the largest specimens in Southern California grows at the MEMBG corner of South Tiverton and Charles E. Young Drive. This fine tree, with pinnately compound, opposite leaves, is more than ten meters tall and exhibits shapely fluting of its trunk. There is also a pair of specimens in the courtyard between Young Hall and Slichter Hall. Whenever it receives good heating, this flamboyant plant can produce magnificent masses of red flowers from March through November. In Westwood, fruits rarely form. Spathodea is widely planted and has become escaped in many tropical locales, such as on Kauai in the Hawaiian Islands. A variant of this species, with yellow-orange flowers, is also cultivated, but reportedly comes true from seed only 1 percent of the time.
Not surprisingly, Mildred Mathias wrote about bignons (see Color for the Landscape, 1964), including, in 1954, an article on the sausage tree, then called Kigelia pinnata but now referred to as K. africana (Lasca Leaves 4:50-51). In fact, a former UCLA undergraduate remembers how a spry Professor Mathias once climbed a sausage tree to hand-pollinate the flowers. By far, this is the most talked about tree on the UCLA campus, and every year MEMBG gets inquiries about two large specimens located on the south side of Moore Hall. It would seem that the typical observer is less impressed by the whorled, pinnately compound leaves than by the reproductive structures, which are produced on long axes that hang as low as two meters below the branches. The large flower of the sausage tree is mauve-red, with a bright yellow, V-shaped anther atop each of its four stamens. In central Africa, as well as here on campus, bats can enter these wide-open flowers to affect pollination. In fact, it is believed that the flowers hang far below the boughs so that bats, using echolocation, are not injured by bumping into the branches. From the ovary of the flower forms the "sausage"--a large, cylindrical, fleshy fruit with a tannish cover--which can become nearly two feet in length. Unlike most other species of Bignoniaceae, Kigelia has fruits that never split open, and its seeds are not winged; instead, naturalists have observed these fruits being walked on and eaten by hippopotamuses and other large African herbivores. The two trees at Moore Hall produce fruits regularly but no seedlings. The largest specimen in the area grows near the loading dock at Murphy Hall. This plant is seven meters tall and has a trunk diameter of 0.6 meters, but typically does not form fruits.
The botanical garden has several other species of bignoniaceous trees. Opposite The Patio you can view a fairly tall Radermachera sinica, native to Southeast Asia. Our specimen has cream-colored rather than the typical pure-white, long-tubed flowers. This species has large and very distinctive twice-pinnately compound leaves. Delostoma lobbii, growing along South Tiverton facing the Factor Building, is an unusual species with opposite, simple leaves and rose-red flowers shaped like lipsticks. Quite different from these is the temperate genus Catalpa. Around Los Angeles County, C. bignonioides is sometimes used as a street tree. The catalpas have white flowers marked with yellow and purple-brown, and the fruit is a long, skinny "bean" (capsule).
Shrubs
In the desert garden at MEMBG grows a young, shrubby specimen of desert willow from California desert springs and washes. When it eventually blooms, this plant will have large, lavender flowers.
Tecoma stans (from the southernmost United States to northern Argentina) and T. guarumae (from South America) are shrubby species in a genus that has bright yellow flowers. You can see these species above the parking lot next to the garden office. MEMBG grows additional species, as well, along with one interspecific hybrid, Tecoma X smithii. This plant has tubular orange flowers, and covers a section of the northern fence opposite Hershey Hall.
In the parking lot you will also find the pinkish-flowered X Chitalpa tashkentensis, a delightful intergeneric hybrid between Chilopsis linearis and Catalpa bignonioides that was produced in Uzbek (central Asia). MEMBG has the two original clones of this hybrid: "Morning Cloud" has pale pink flowers, and "Pink Dawn" has deep pink flowers.
Undoubtedly the most surprising shrub of the Bignoniaceae is the genus Rhigozum, which MEMBG cultivates close to the desert garden. This genus has remarkably small, microphyllous leaves, which is typical of desert and thorn scrub communities. Rhigozum obovatum has trifoliate leaves on rapidly growing long shoots and simple leaves on short shoots.
There are many other bignon shrubs and trees in the MEMBG collection, such as species of Markhamia and Boldia, that are worthy of discussion, but space does not permit complete descriptions of all species.
Climbers
Tecomaria, the cape honeysuckle, is often grown as a shrub, but if given a trellis or plant support, Tecomaria will become a showy climber. There are numerous plantings of cape honeysuckle clones around the perimeter fence of MEMBG, easily viewed along the South Tiverton fence line. Also on that fence you will see trumpet creeper (Campsis radicans). A favorite climber of the eastern United States, this species has broad orange-red flowers (typical form), as well as the yellow flowers exhibited by our specimen (called variety flava).
Most bignon species are obligate lianas whose foliage and showy flowers grow on the canopies of tropical forest trees. This makes the bignons particularly difficult to study, because the plants are so far above the ground. Also, idiosyncratically, bignons tend to thrive on the edges of canopies and between canopies--places that climbers often cannot safely reach. (As an aside, the world's expert on Bignoniaceae, Alwyn H. Gentry, died tragically from falling--not from the canopy but rather in a plane crash while surveying tropical vegetation.)
Around Westwood you will find several showy bignon lianas, many of which are now available at commercial nurseries. Real eye-pleasers that have been grown in our city include the species of Cydista, Clytostoma, Distictis, Macfadyena (formerly Doxantha), Pachyptera, and the red-flowered Pyrostegia (for a really hot spot, best in southern desert climates). Members of this group of lianas are relatively easy to recognize as bignons because they have opposite, trifoliate leaves in which the terminal leaflet on climbing shoots develops as a tendril.
The fence at the base of the drive in MEMBG is adorned by Pithecoctenium crucigerum, planted there in 1996. This genus is distinctive among bignons for having tendrils that branch more than once, hexagonal stems, and pseudo-stipules in the leaf axils. Our plant has not yet bloomed, but should have white flowers. Pithecoctenium is called monkey-comb because its large, flat fruits are covered with thousands of spine-like emergences. Similar lianas are the pink-flowered Clytostoma callistegioides (orchid trumpet vine) and the yellow-flowered Macfadyena unguis-cati. Opposite UCLA's medical bookstore in the Center for the Health Sciences is a splendid specimen of Distictis buccinatoria, often referred to as red trumpet vine. The royal trumpet vine, a lavender interspecific hybrid called Distictis X riversii, was doing well at the top of MEMBG's Hershey Slope until the terrible landslide of 1996. Garden staff recently obtained and planted out other beauties from this family, including Anemopaegma orbiculatum, a tendrillar liana from Central America with four or five leaflets, light yellow flowers, and flat, circular fruits and seeds.
Pandorea and Podranea are lianas with pinnately compound leaves that lack tendrils. Fairly common in the area are the lavender-flowered Podranea ricolasiana and the white-flowered Pandorea jasminoides. These species grow rapidly in full sun, especially where heat reflecting from a wall encourages the plants to flower profusely.
The botanical garden is, of course, a place to see other Bignoniaceae that are cultivated in Southern California, and we will continue to "push the envelope" by attempting grow tropical species outdoors. The bignons are tropical and subtropical species, for the most part, and require substantial heat to stimulate flowering. We have not been successful in keeping Pyrostegia venusta (flame vine) or Crescentia cujete (calabash, a tree forming large, spherical, indehiscent fruits from bat-pollinated flowers on the main trunk and large branches), for example, because these species need a warmer climate than we can provide.
Success in growing Bignoniaceae rests mostly on the ability to provide a hot or very warm microhabitat. Try a bignon, and be pleasantly surprised!