Twin Cress forms as a circular mat with hairless, fringed leaves on alternate sides of the stems. There tend to be more leaves on one side of the steam than the other (which is a distinguishing characteristic, as is the distinctive smell of the crushed leaves). Stems are initially fragile, but later become tougher and sprawling. It has small white flowers, and pairs of pods.
Typically germinating in spring and autumn, it is an annual which can germinate at any time through the year, most commonly in bare soil. It struggles in established pastures.
The weed is a problem on dairy farms as it will result in tainted milk, which processors may reject.
It is sometimes mistaken for wireweed, and incorrectly called field cress.