Sterculia foetida L.

Branch Structure

Sterculia foetida L. has horizontally spreading branches arranged in whorls.

Bark Characteristics

Its bark is smooth and gray.

Leaf Petiole Traits

Leaves grow at the ends of branchlets, with petioles between 12.5 and 23 centimetres (4.9 and 9.1 inches) long.

Leaf Blade Structure

Leaf blades are palmately compound, holding 7 to 9 leaflets. The leaflets are elliptical, 100–170 mm long, and have short petiolules.

Foul Odor Trait

Both the petioles and flowers of this plant produce a foul odor. Plant explorer David G. Fairchild, who personally smelled many of the world's foulest-smelling flowers, considered Sterculia foetida to have the worst smell of all.

Flower Inflorescence

Its flowers are arranged in panicles 10–15 cm (4–6 in) long.

Flower Sex Characteristics

The large green or purple flowers are unisexual, as the species is dioecious, meaning male and female flowers grow on separate individual trees.

Pollen Grain Traits

Its pollen grains are oval in shape, around 40 microns in length.

Calyx Characteristics

The calyx is dull orange and split into five sepals, each 10–13 millimetres (3⁄8–1⁄2 in) long.

Fruit Structure

The fruit is made up of four to five follicles, and each follicle usually contains 10 to 15 seeds.

Ripe Follicle Color

Ripe follicles are scarlet in color.

Flowering and Leaf Emergence Timing (India)

In most of India, this species flowers in March, and new leaves emerge between March and April.

Flowering and Fruit Observation (Hyderabad 2015)

In Hyderabad, India, flowering was recorded in September–October 2015, with ripe fruits on the upper sections of the tree and young unripe green fruits on the lower branches.

Fruit Ripening Timeline

Fruits ripen in February, 11 months after flowers appear.

Global Distribution

Sterculia foetida occurs naturally or has been found in India, Bangladesh, Taiwan, Indochina, the Philippines (where it is called kalumpang), Hawaii (United States), Indonesia, Ghana, Australia, Mozambique, and Togo.

Seed Oil Biofuel Potential

The oil from Sterculia foetida is comparable to sunflower, soybean, and grapeseed oils for use as a biofuel.

Seed Oil Fatty Acid Composition

This oil contains cyclopropene fatty acids (CPFA), specifically malvalic acid (8,9 methylene-heptadec-8-enoic acid) and sterculic acid (9,10-methylene-ocadec-9-enoic acid).

Seed Oil Biofuel Compliance

Its measured flash point, iodine value, free fatty acid content, phosphorus content, cloud point, pour point, viscosity at 40 °C, oxidative stability at 110 °C, density, and trace metal content all fall within the ranges specified by ASTM and EN biofuel standards.

Seed Edibility Notes

Available evidence notes that the seeds are edible but have a purgative effect, and recommends roasting them before eating.

CPFA Health Risks

One published review states that CPFA such as sterculic acid are carcinogenic and co-carcinogenic, and cause a range of biological effects in animals; according to this review, CPFA present in food is dangerous to human health.

Vietnamese Common Name and Use

In Vietnam, this tree is called Trôm, and its sap is harvested to make a soft drink called "Mủ Trôm".