Bitterberry grows to about a person’s height, a loose, arching shrub with smooth, purplish-grey stems and narrow, pointed, willow-like leaves that are dull green above and pale below. In early summer it bears small greenish-white flowers in clusters along the stems, smelling faintly of honey and cut grass. By late summer they have become bunches of round berries the size of a pea, green, then red, then a glossy purple-black that stains fingers dark red. Bruised, leaves and bark give off a bitter, almond smell.

It wants the shade and damp of ravine sides and the edges of slip-slopes, where the forest breaks and light comes through. It grows nowhere outside the Briarreach and its ravine edges, and it is commonest in the deep cut of the Sallow.

A bitterberry shrub roots where its arching stems touch the ground, and a ravine side can hold a thicket of them. Birds eat the berries without harm and spread the seed; beasts that browse the shrub sicken and learn to leave it.

It flowers and fruits each year from its third or fourth, and the berries hang into the first frosts. A shrub lives a few decades and renews itself from its rooting stems.

The berries and leaves kill. A child who eats a handful vomits, cramps, and grows drowsy and cold within the hour, and may not wake; a grown body sickens hard and usually lives (see Poison Herbs). The Thornbound crush the berries into bait for rats and martens at their stores. Boiled with iron-rich mud and bark, the berries give the dark dye of Thornbound hedge cloth, which goes out through the Waitfield with the other dyes. Dyers wear gloves and wash in running water.

Ravine Trolls leave bitterberry standing along crossing approaches, since nothing grazes it and its roots hold soft soil.

Thorn Elves say bitterberry is the forest’s first lesson: "the sweetest thing in the ravine is the one that wants you there." It is planted at the edge of some circles as a warning to their own children. Basin traders who buy the dark cloth at the Waitfield believe the dye is poisonous to wear, which it is not once washed. Trolls say a crossing family that lets its bitterberry be cut has forgotten where its children play.

Frontier tales tell of a Human war-band that ate the berries on a forced march through the ravines and was found by the Thornbound three days later, half of it dead in the thicket; poisoners in the basin towns pay well for the berries for the same reason.