Plant Novelties: Talauma hodgsonii

One fascinating evergreen species cultivated at MEMBG is Talauma hodgsonii Hooker f. & T. Thomas (family Magnoliaceae). The genus Talauma is very closely related to, and often treated as part of, the genus Magnolia. Talauma hodgsonii is native to foothill forests of the Himalayas, occurring up to 1,700 meters elevation, and it was introduced into horticulture during the 1930s but still is seldom planted anywhere. Our 12-meter specimen is growing well in a shaded part of the botanical garden, and itself shades part of the Fern Grotto.

This talauma has tough (coriaceous), very large, petiolate, alternate, obovate leaves--some nearly half a meter in length--that have conspicuous pinnate venation, and the blade is folded upward along the midvein. The leaf surface totally lacks hairs (it is glabrous), and the margin of the blade is entire and gently undulating. When formed on a flush of new vegetative growth (that is, after flowering occurs), the young blades are rose-purple before they mature green, and quite stunning!

Leaves of all Magnoliaceae (220 species total) possess conspicuous stipules. The stipule of each leaf is actually a pair of fused stipules, called an ochrea, which is attached mainly to the stem, rather than to the petiole. In this family, the ochrea completely encircles the stem, and when the stipule abscises (it is soon deciduous), there results a circular (annular) stipular scar around the stem. Such annular stipular scars are conspicuous on stems of T. hodgsonii, but they even persist on older stems for several years after the light-brown bark covers the surface. Similar annular scars are present in figs (Ficus). (Parenthetically, at the recent Los Angeles Times Festival of Books held at UCLA, a couple from Louisiana was sitting beneath a campus tree, which they called a magnolia, but I had to tell them that they were, instead, sitting beneath a fig tree. Were they confused by the annular stipular scars?)

Seeing the flowers of our talauma--in bud, when they open, and as they age--is definitely worth a visit to MEMBG. Somewhat smaller than its cousin the southern magnolia (Magnolia grandiflora), the flower of T. hodgsonii can be 17 centimeters across and has the delightful fruity fragrance of a guava (Psidium). Buds, formed at the tips of last year's shoots, are subglobose, remarkably 5 to 7 centimeters in diameter, and colored "dusty" plum. Dusty refers to the presence on the bud of loose wax, termed epicuticular wax, that can be easily rubbed from the surface, as on a red grape or Italian plum.

After the flower bud cover, like an ochrea, splits and falls off, the stiff flower unfurls. There is an envelope of nine "sepals" and "petals" (perianth parts) that are light rose-beige, each like a thick, spoon-shaped ladle (4 to 6 centimeters wide) that you could, literally, use to eat soup. Transparent ethereal oil cells, abundant on the upper surfaces of the petals, release the fruity fragrance. The center of the flower appears like an intricate, light-tan banister ornament, containing at the base about 200 stamens, tan with red-violet bases, that are arranged in a helical fashion (in a 13/34 phyllotaxis). Above the set of stamens are the 80 or so flame-shaped pistils. Unlike typical stamens of plants, the primitive-looking stamens in magnoliads are broad, thick, and fleshy (botanists call these laminar stamens) with long sacs of pollen on one side. Each pistil bears at its tip and on the inner face hairs of a primitive-type of stigma. With a hand lens you can also see that the pistils have numerous white fragrance cells.

As the flower ages, the lowest stamens are shed, and they often collect in the spoon-shaped petals. Now can be seen a solid cone in the center of the flower (the torus) revealing helically arranged scars of the stamens. Eventually only the pistils remain firmly attached to the torus. Following pollination, each pistil develops as a dry woody fruit (a follicle) that at maturity forms a vertical opening. From that purse-like opening may dangle a single, large, red-orange seed on a long thread-like funiculus. At MEMBG I have not yet observed fruits with seeds, but this is the same structure (many follicles and attached to a woody torus with dangling seeds) that is also characteristic of Magnolia grandiflora.

Much has been written about the interesting flowers, fruits, and seeds of these magnolias. Experts tell us that they are pollinated by a particular group of beetles that are attracted by the fruity fragrance and then forage on the fleshy stamens to consume the protein-rich pollen. This type of pollination is termed cantharophily. Such beetles are imprecise pollinators, clumsily walking over the stigmatic surfaces and depositing pollen grains, only one of which is needed to form the seed of each fruit. The brightly colored seed, literally hanging by a thread, is displayed there for birds that are the agents of dispersal.

ARTHUR C. GIBSON,MEMBG Director

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