Aeschynomene elaphroxylon also known as an ambatch, pith tree or Balsa wood tree is a common large shrub to small tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

 of the genus Aeschynomene

Aeschynomene

Aeschynomene is a genus of flowering plants in the family Fabaceae. They are known commonly as jointvetches. These legumes are most common in warm regions and many species are aquatic...

in the Fabaceae

Fabaceae

The Fabaceae or Leguminosae, commonly known as the legume, pea, or bean family, is a large and economically important family of flowering plants. The group is the third largest land plant family, behind only the Orchidaceae and Asteraceae, with 730 genera and over 19,400 species...

 family. It can grow up to 9 m high, with spiny stems, and pairs of substantial thorns under the base of leaves.

A. elaphroxylon is indigenous to parts of tropical Africa. It typically grows by water and in water logged soils, such as by rivers, lakes and swamps in countries like Ghana

Ghana

Ghana , officially the Republic of Ghana, is a country located in West Africa. It is bordered by Côte d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south...

 and Nigeria

Nigeria

Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...

, but is widespread across tropical Africa to Ethiopia

Ethiopia

Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...

 and Sudan

Sudan

Sudan , officially the Republic of the Sudan , is a country in North Africa, sometimes considered part of the Middle East politically. It is bordered by Egypt to the north, the Red Sea to the northeast, Eritrea and Ethiopia to the east, South Sudan to the south, the Central African Republic to the...

, and further south and east in Zimbabwe

Zimbabwe

Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...

.

The seeds of A. elaphroxylon have been known to stay viable after being buried for a few years in the waterlogged banks where it grows well. The seeds are contained in pods that grow in flattened, erect spirals on the tree. The tree has nitrogen fixing nodule

Root nodule

Root nodules occur on the roots of plants that associate with symbiotic nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia...

s in its stem.

In Ethiopia the species can be found in the Nechisar National Park

Nechisar National Park

Nechisar National Park is one of the National Parks of Ethiopia. Located in the Southern Nations, Nationalities, and Peoples Region immediately to the east of Arba Minch, its 514 square kilometers of territory include the "Bridge of God" , and the Nechisar plains east of the lakes...

.