Hura crepitans

Hura crepitans, the sandbox tree, also known as possumwood, monkey no-climb, assacu (from Tupi asaku) and jabillo, is an evergreen tree in the family Euphorbiaceae, native to tropical regions of North and South America including the Amazon rainforest. It is also present in parts of Tanzania, where it is considered an invasive species. Because its fruits explode when ripe, it has also received the colloquial nickname the dynamite tree.

Description
The sandbox tree can grow to 60 m, and its large ovate leaves grow to 2 ft wide. They are monoecious, with red, un-petaled flowers. Male flowers grow on long spikes, while female flowers grow alone in leaf axils. The trunk is covered in long, sharp spikes that secrete poisonous sap. The sandbox tree's fruits are large, pumpkin-shaped capsules, 3 - 5 cm long, 5 - 8 cm diameter, with 16 carpels arranged radially. Its seeds are flattened and about 2 cm diameter. The capsules explode when ripe, splitting into segments and launching seeds at 70 m/s. One source states that ripe capsules catapult their seeds as far as 100 m. Another source states that seeds are thrown as far as 45 m from a tree, averaging about 30 m. High-speed video analysis of its exploding fruit revealed that Hura crepitans seeds fly with backspin as opposed to topspin, which was previously assumed. Backspin helps seeds remain oriented to minimize their drag during flight.

Habitat
This tree prefers wet soil, and partial shade or partial to full sun. It is often cultivated for shade. Sandbox trees are tropical trees and prefer warmer, more humid environments.

Uses
Its wood is light enough to make indigenous canoes. Fishermen have been said to use the milky, caustic sap from this tree to poison fish. The Caribs made arrow poison from its sap. The wood is used for furniture under the name "hura". Before more modern forms of pens were invented, the trees' unripe seed capsules were sawn in half to make decorative pen sandboxes (also called pounce pots), hence the name 'sandbox tree'. It has been documented as a herbal remedy.

The seeds contain an oil that is toxic for consumption but can be made into biodiesel and soap; its starchy leftovers can be made into animal feed after cooking.