Aristolochia gigantea Mart. & Zucc.
Aristolochiaceae
Rare evergreen climbing vine preferring the moderate insolation levels of older secondary, or disturbed primary, forests. Aristolochia remains inconspicuous until it produces the large, showy, lavender flowers that are its hallmark.
Description: Aristolochia gigantea is a climbing vine that grows to heights of several meters by twining its stem around the thin trunks and branches of understory shrubs and treelets. Basal portions of the stem can live for years and become quite thickened – reaching 4 or 5 cm in diameter. Older stems also develop thick, corky layers of tan-colored bark, characteristically contoured by deep, vertical grooves. Foliage is found only on the actively growing parts of the vine, where stems are thin, green and fresh. Aristolochia leaves are large, simple, and alternately arranged. The smooth, entire blades are thin and of cordate (heart) shape. A pattern of five, palmate main veins traverses the blade and converges at its base, where a long (5 cm) petiole is attached.
Flowers emerge from the lower, woody, leafless portion of the vine. Each is composed of a large (16 cm by 12 cm) and stunning, orbicular calyx (petals are lacking) of finely mottled maroon and white coloration. Though smooth, the maroon portions of the flower appear velvety and raised. In the center of the calyx is a projecting lip that covers an opening that leads into the interior of the flower, where the stamens and pistil are located. Bearing some resemblance to the pitchers produced by some carnivorous plants, Aristolochia flowers are nevertheless vegetarian (they do not consume insects!). The intensity and duration of blossoming varies from year to year but flowers are generally present from late October through November, occasionally continuing into December. Fruits are rarely seen but they begin as 12 cm, sausage-shaped capsules, also found growing on the lower, thick-barked portion of the vine. When mature, they dry and split into five sections, releasing many minute, winged seeds. Capsules mature in February and March.
Similar Species: Aristolochia‘s heart-shaped leaves, coupled with its twining habit and cork-barked base, make the identification of this species simple and sure.
Natural History: According to Barry Hammel (personal communication, August, 1989), Aristolochia flowers attract certain classes of insects by producing an odor similar to that of rotting animal flesh. The purple color of the blossoms also appears to allure them. Once inside the flower, these insects are utilized for purposes of pollination – rather than nutrition.
Uses: The unusual and striking flowers of Aristolochia gigantea easily qualify it for cultivation as an ornamental species.
Distribution: In Manuel Antonio National Park (MANP), Aristolochia is found in the semi-shade of old, secondary forests as well as in primary forest light gaps. It ranges from Costa Rica to Panama.
Images: Stem Leaf Flower Bud Flower Flower2 Flower3 Fruit Fruit2
Trees of Costa Rica's Pacific Slope 
