Eysenhardtia polystachya aka Kidneywood

Eysenhardtia polystachya is a shrub or small tree from Mexico. It is part of Fabaceae, the pea family. People call it Mexican kidneywood or lignum nephriticum. It grows in central and southern Mexico. It lives in grassland and dry woods of several kinds. Some woods are open, and some have thorny plants. Others are deciduous, which means their trees shed their leaves. Its home climate has a dry season.

This plant sheds its leaves and grows many branches. Its usual height is 5–16 feet [1.5–5 metres]. Some plants reach 23 feet [7 metres]. Its trunk can grow about 0.8 feet [0.25 metres] across. The source also gives a general height of 13 feet [4 metres]. Bees carry pollen to its flowers. People cook and eat the whole flower cluster, called an inflorescence. The accounts give no facts on flower colour or fruit.

In gardens, it grows best in full sun. It will also grow in light shade. Yearly rain varies widely in the places where it grows wild. Its range spans both tropical and subtropical parts of Mexico. It copes with cuts and grows new shoots from old wood. This lets gardeners renew the plant's main branches. Reports say it does not fix nitrogen, unlike many pea-family plants. The evidence gives no frost limit or hardiness zone. It names no specific pests or diseases either.

The wood has uses beyond the garden. It gives a yellow-brown dye for cloth. The bark is a source of tannins. The heartwood is red-brown and has black streaks. It is hard and heavy, with a fine grain. It also lasts well. Workers polish it to make small items. These include cups and other vessels that hold water. Soaking the wood in slightly alkaline spring water makes the water glow through fluorescence. Against a dark background, the water looks blue. With other light and backgrounds, it shows yellow or orange-gold tones.

In Mexico, traditional medicine uses the wood and bark for urinary complaints. Other reported uses treat pain, fever, inflammation, and diabetes. These records show use as medicine, not proof of safe treatment. The source lists no known hazards. Yet it gives no detailed safety review. People gather wild plants for food, medicine, and wood. Past trade took the wood to Europe and the United States. Useful Tropical Plants reports a 2013 IUCN listing of Least Concern. Its account says the species grows across a wide range. Its population is stable, with no known major threats.