plant that bears biennial stems ("canes") from the perennial root system. In its first year a new stem grows vigorously to its full length of , trailing along the ground or arching up to 4 m high. The stem is stout, up to 2-3 cm diameter at the base, and green; it is polygonal (usually hexagonal) in cross-section, with fearsome thorns up to 1.5 cm long forming along the ribs. The canes can turn more red/purple if they are exposed to bright sunlight. This is common in the summer.

The leaves