The wild radish Raphanus raphanistrum is an annual herbaceous plant in the cabbage family Brassicaceae. Many members of this family have been selectively bred as food plants (including cabbage, broccoli and rapeseed) and R. raphanistrum is the wild relative or ancestor of the edible radish Raphanus sativus. The Brassicaceae can be identified by their characteristic flowers (four free petals in a cross-like arrangement), alternate leaves, and fruits which are long capsules sometimes with a beak (siliqua), or a short or flattened capsule (silicula).
R. raphanistrum germinates rapidly, and spreads easily in disturbed habitats such as roadside verges. Discovered growing in an entangled clump in the Harris Garden, the mature plants had smooth stems up to a metre long, and all plants had developed the distinctive siliqua fruits of this species, which appear beaded and with a long beak. Leaves are alternate and lobed with fine hairs on the underside. The cruciform flowers of R. raphanistrum often vary in colour from white to mauve to yellow, and are about 15mm in diameter. Both white and yellow flowered plants were found growing in long grass behind the apple tree plots.