Flourishing in our display of plants from mediterranean-type climates is Cordia decandra Hooker and Arnott (family Boraginaceae), a Chilean plant species originating from the transition between desert scrub and mattoral north of Santiago. In Chile this evergreen shrub or small tree has the vernacular names carbón and carbonillo, indicating that it was used for making charcoal. In the past, C. decandra probably was used there for fueling copper smelters. For centuries, cut pieces of wood were burned in pits covered over with soil, thereby producing charcoal in a low-oxygen environment. It has been a common practice in Latin America to use charcoal in fires, because it burns longer than wood. The wood of C. decandra is very dense and so has been used for carving also. Cordia L. is a genus of approximately 300 species, nearly all of which are native to frost-free habitats in the Old and New World tropics and subtropics, and several of the large trees in the genus are harvested for fine dark timber.
Anyone approaching this plant might initially mistake it for a species of Cistus. That actually is a reasonable error-until you see the flowers-because the leaves are similar in size and shape, and species of Cistus are natives of chaparral-type vegetation in southern Europe, i.e., maquis. However, leaves of Cordia are helically alternate on the brown stems, whereas they are opposite decussate in Cistus. The narrow lanceolate leaves of C. decandra are mostly 25 to 55 millimeters in length, rarely longer, and have very short petioles; they are generally less than a centimeter apart on the stem and tend to be perpendicular to the stem or even somewhat reclined. The leaf margin is entire, and the raised green, minor veins are fairly conspicuous on the lower side. One way to recognize this borage is to feel the semi-glossy upper leaf, which feels like fine sandpaper. Boraginaceae generally have scabrid or hispid leaves, bearing stiff, apex-pointing, one-celled hairs that are almost always bristly to the touch. These hairs are present on both leaf surfaces.
Cordia decandra has delightful white flowers, about 2.5 centimeters wide and long, that adorn our shrub for more than half the year, especially during winter and spring. Each rapidly formed vegetative shoot will form an inflorescence of generally eight to 12 flower buds. These buds are truly remarkable in having a nest of black hairs on the five-lobed calyx-yes, black! Atop the calyx are about ten greenish appendages, which make the young bud look instead like a developing fruit with attached stigmas. The flower opens to a pure white corolla, funnel-shaped and with ten lobes of the fused petals. The filaments of ten stamens (decandra = 10 males) are fused to the throat of the corolla (stamens are epipetalous) and so the white anthers project in a ring about a centimeter from the tube. Through the center emerges a simple style with two stigmas. The ovary is conical but has ten scalloped lobes around the base. This ovary should mature into a somewhat fleshy drupe, but our specimen has, to our knowledge, never produced seedlings.
It is appropriate to mention that the white flowers of certain species of Cordia have the standard characteristics of the hawkmoth flower. Whether hawkmoths visit C. decandra remains to be determined, although the opening of the flower is so wide and the fragrance so light that another pollinator is more likely.
So far, we have no complaints about the plant growing at MEMBG. Our plant has been pest free and stayed less than 1.5 meters tall without any regular pruning, even though in the wild it can exceed 4 meters in height. Perhaps this means that the plant is self incompatible, meaning that pollen from the plant is not effective in forming seeds on the same genetic individual. Some would be disappointed by hearing that, but we are not; before there is any talk about introducing Cordia decandra to Southern California nurseries for xeroscapes, we need to know about its reproductive biology.
ARTHUR C. GIBSON, MEMBG Director