The Tropical House is currently closed due to construction.

Hibiscus schizopetalus

Hibiscus schizopetalus

The surface area of the Earth between the Tropic of Cancer (latitude 23.5° N) and the Tropic of Capricorn (latitude 23.5° S) represents the Tropics, or the Equatorial Zone. The Equator is at 0° latitude. The word “tropics” might conjure images of lush, steamy rainforest but surprisingly over 75% of the tropical belt endures periods of annual drought. The Tropics include desert, savanna, woodland, wetland, and rainforest, each with its own distinct climate, flora, and fauna. Prevailing wind conditions, elevation, and distance from the ocean are all contributing factors in the different tropical climates.

Rainforest plants grow in four distinct layers: the giant emergent trees, the towering canopy of broadleaf evergreen trees, the shorter understory (or lower canopy) trees intertwined with vines and shrubs, and the shady forest floor. Rainforests experience annual rainfall exceeding 2 meters (80–90 in), sometimes more than 7.5 meters (300 in or 25 feet)!

Titan Arum

One of the most famous plants in this collection is the titan arum (Amorphophallus titanum). This plant is native to the rainforests of Sumatra, Indonesia. They produce one of the world’s largest flowering structures to lure insects with the illusion of decay—having both the appearance and odor of rotting flesh; hence the plant’s common name, “corpse flower.”

Titan arums produce only one leaf at a time, but they’re one of the world’s largest leaves. A young titan arum produces a relatively small leaf, but each leaf it produces is bigger than the previous leaf, eventually reaching 3 to 5 meters (10–15 ft) tall—as large as a small tree! The leaf photosynthesizes, making sugars that are stored as starch in a swollen, underground stem (corm). The corm must reach at least 14 kg (30 pounds) before blooming may occur; corms have been known to weigh up to 90 kg (200 pounds). A leaf withers after about 16 months and the titan arum goes completely dormant for four months or longer. When it next sprouts, the corm will produce either another single leaf or a bloom. Because flowering takes so much energy, the corm produces one leaf after another for years before blooming again. It’s typically 6–7 years before a titan arum blooms for the first time, but it may take much longer. The flowering structure may take months to form, but only remains open for a day or two while pollination may occur. Without pollination, the whole structure collapses and the cycle repeats.

A titan arum bloom appears to be the world’s largest flower, but it is actually a stalk of many flowers (an inflorescence). Hundreds of tiny, petal-less flowers are clustered at the base of the yellowish-gray, phallus-like structure (spadix) that can grow to be over 3 meters (9 ft) tall. The flowers are hidden from view by a large, pleated, skirt-like covering (spathe) that is light-green and speckled cream on the outside and deep maroon on the inside.  If pollination takes place, the spadix remains firm while the fruits develop over a period of months.

In October 2018, a corpse flower known as Maladora opened at the UC Botanical Garden. Below is a video by PBS explaining the adaptations of the plant to attract pollinators and showing the flower’s bloom cycle.