information:classification
Plants

Blackberries are perennial plants bearing biennial stems (called canes) from their roots.

In its first year, a new stem, the primocane, reaches a full length of about 3–6 metres (9.8–19.7 feet) trailing on the ground and bearing large palmate compound leaves with 5–7 new leaves; it does not produce any flowers. In its second year, the cane is a floricane with a non-growing stem. The lateral buds open to produce flowering laterals. First- and second-year shoots produce short-curved, sharp thorns. Thornless cultivars have been developed during the early 21st century.

Unmanaged plants tend to aggregate in a dense tangle of stems and branches, which can be controlled in gardens or farms using trellises. Blackberry shrubs can tolerate poor soils, spreading readily in wasteland, ditches, and roadsides.

The flowers bloom in late spring and early summer on the tips of branches. Each flower is about 2–3 centimetres (3 ⁄ 4 – 1 + 1 ⁄ 4 inches) in diameter, with five white-pink petals. The fruit only develops around ovules fertilized by the male gamete from a pollen grain. The most likely cause of undeveloped ovules is inadequate pollinator visits. Incomplete drupelet development can signal infection with raspberry bushy dwarf virus.