Strychnos potatorum aka Chillam

Strychnos potatorum is a deciduous tree in the Loganiaceae family. Its common names include clearing nut and water filter tree. It grows in India, Sri Lanka, Myanmar, and Madagascar. Its African range runs from Rwanda south to Limpopo. It comes from tropical lands with a dry season. Wild plants grow in woodland, bushland, and forests along rivers. They also grow beside dry riverbeds and on termite mounds.

The tree grows slowly and forms many branches. Garden references give a height and spread of 39 feet [12 metres]. Other accounts record heights of 13–59 feet [4–18 metres]. Some plants take a shrub form rather than a tree shape. The trunk can reach about 3.3 feet [1 metre] across. Pale grey bark covers the trunk. The thin, oval leaves are glossy and green. The tree can send up new shoots from its roots.

Clusters of small flowers range from white to yellow-green. The round berries have smooth skins and turn black when ripe. Each fruit measures about 0.04–0.06 feet [0.012–0.018 metres] across. A firm outer wall surrounds whitish pulp and one or two seeds. People sometimes eat young fruit or make it into preserves. The pulp also has a recorded food use. The fruit forms part of an Ayurvedic coffee substitute. These uses do not establish that every plant part is safe. Crushed fruit and bark serve as fish poisons.

This tree grows beneath the canopy of deciduous woodland. It accepts deep shade as well as partial shade. Sandy, loamy, and clay soils can suit it. The soil should drain well, but may be dry or moist. It accepts mildly acid, neutral, and mildly alkaline conditions. Established trees withstand drought well. PFAF lists USDA hardiness zones 10–12. Seeds need deep pots or direct sowing because their taproots are delicate. Cuttings from partly mature wood and root suckers offer other propagation routes.

The seeds have a long use in clearing cloudy water. Compounds in them help suspended matter settle to the bottom. This process improves clarity but does not prove drinking water is safe. Local markets sell seeds gathered from wild trees for this use. The hard, close-grained wood resists termites, though it splits easily. Traditional medicine uses the leaves, roots, and seeds for many complaints. Recorded uses include eye pain, coughs, and digestive problems. These records describe traditional practice rather than proven treatments.