Thalia geniculata aka Arrowroot

Thalia geniculata is a large herb in the Marantaceae family. It is a perennial, so it lives for years. The RHS lists swamp lily as a common name. It is native to tropical Africa and much of the Americas. Kew includes the southeastern United States in its native range. Useful Tropical Plants gives more facts on its African range. It spans Senegal to Sudan, south to Angola and Zimbabwe. In the Americas, it grows from Argentina north to Mexico. It also occurs in the Caribbean. It is not native to Britain or Ireland.

The plant grows from a tuberous rhizome below the ground. Kew calls it a rhizomatous geophyte, reflecting this below-ground growth. It has stout, soft stems rather than woody ones. Useful Tropical Plants gives heights of 6.6–13.1 feet [2–4 metres]. It also gives a separate height of 9.8 feet [3 metres]. These heights refer to the species as a whole. They do not confirm a size range for garden plants. The supplied species account gives no width for the plant. It gives few details on the leaves and stems. Photos on that page show flowers and seed capsules. Their captions give no more facts about these parts.

Kew places this species in wet tropical climates. In Guatemala, it grows in open swamps with shallow water. These swamps lie at or close to sea level. These records place it in wet ground, not dry sites. They do not show its exact water needs in gardens. Useful Tropical Plants lists the plant's status as wild. That source gives no steps for growing the species. It lists seed as a way to grow new plants. The supplied species evidence gives no light needs or hardiness limits.

People gather the plant from the wild for local food use. Useful Tropical Plants lists both leaves and roots as edible. It says to cook the roots, which includes baking them as a vegetable. The roots also yield starch for an arrowroot-like food. The source does not say how to prepare the leaves. It lists no known hazards but does not assess pet safety. It lists no known medicinal or other uses. The supplied species accounts do not describe pests or diseases. They give no flowering season for the species. Nor do they give guidance on its use in landscapes.