LAURACEAE (laurel family)

Plants shrubs and trees, sometimes colonial from rhizomes and/or root suckers, dioecious (with perfect flowers elsewhere), often incompletely so (pistillate inflorescences then with a few perfect flowers). Leaves alternate, simple, usually petiolate, the blades simple or lobed, the margins otherwise entire. Stipules absent. Inflorescences axillary clusters or terminal racemes produced before or as the leaves develop. Flowers all or mostly imperfect, more or less perigynous, actinomorphic, the buds lacking sheathing bracts, but some of the flowers sometimes with a pair of minute bracts, these shed early. Perianth not clearly differentiated into calyx and corolla, the tepals 6, in 2 whorls of 3, fused basally into a short perianth tube (this sometimes very short or essentially absent), this persistent at fruiting as a small disc or crown, the free portions shed after flowering (persistent elsewhere), relatively thin, usually yellow or greenish yellow (green or white elsewhere). Staminate flowers with 9 stamens (12 elsewhere) in 3 whorls and a highly reduced, nonfunctional ovary, the filaments somewhat flattened, attached to the perianth tube (when present), those of some stamens often with a pair of small nectar-producing basal appendages, the anthers attached at the base, yellow, dehiscing longitudinally by 2 or 4 small flaps. Pistillate flowers with 1 ovary and sometimes with varying numbers of staminodes sometimes also present, these varying from small filaments to seemingly well-formed (but nonfunctional) stamens, the ovary superior, apparently of 1 carpel and with 1 locule, the style and stigma 1. Ovule 1, the placentation more or less apical. Fruits drupes or berries, with 1 seed or stone. About 52 genera, about 2,850 species, nearly worldwide, most diverse in tropical regions.

The description above does not account for the unusual genus Cassytha L. (love vine), which is sometimes segregated into its own family, Cassythaceae. Plants in this genus are parasitic vines with orangish to yellowish, twining stems and small scalelike leaves, superficially similar in appearance to the dodders (Cuscuta, Convolvulaceae). The small, greenish white, perfect flowers are produced in small spikes or spikelike racemes, occasionally reduced to solitary flowers.

The Lauraceae contain many species responsible for several spices and flavorings (some of these mainly used in tropical countries), including cinnamon (Cinnamomum verum J. Presl and its relatives) and bay laurel (Laurus nobilis L.). A number of different tropical genera also are sources for aromatic oils. Camphor originally was extracted from the bark of Cinnamomum camphora (L.) J. Presl. Some of the tropical tree species are harvested for timber. Persea americana Mill. is widely cultivated for its edible fruit, the avocado.

In 2003, conservationists and land managers in some southeastern states began noticing an alarming die-off of redbay, Persea borbonia (L.) Spreng. (and its segregates), another member of the Lauraceae that is native to the Atlantic Coastal Plain. Subsequently, it was discovered that the extensive mortality was being caused by an undescribed species in the pathogenic fungal genus Raffaelea Arx & Hennebert being spread by an invasive exotic ambrosia beetle, Xyleborus glabratus Eichhoff, an Asian insect with which the fungus has a symbiotic relationship (Fraedrich et al., 2008). Symptoms of the disease include the beetle entry holes in the stems, rapid wilting, branch dieback, black discolorations of the sapwood, and death of the affected plant. Currently the pathogen is still restricted to portions of South Carolina, Georgia, and Florida. However, research by plant pathologists has shown that other genera of Lauraceae also potentially are affected by this disease, which is known to infect members of the genera Lindera and Sassafras, as well as potentially cultivated avocado groves. There is concern that the insect vector eventually will disperse the pathogenic fungus throughout the eastern half of the United States and that there might be rangewide future declines of all of the species of Lauraceae that occur in Missouri.