Woodiness

Woodiness is the characteristic of plants to develop and maintain woody tissue, primarily secondary xylem produced by the vascular cambium. In woody plants, stems and roots gain rigid structure through lignified cell walls, enabling greater height and longevity compared with herbaceous vegetation.

Wood is composed of xylem cells such as tracheids and, in many angiosperms, vessel elements, along with sclerenchyma fibers and parenchyma; the lignin-rich secondary walls confer strength and resistance to decay. Growth rings, formed by differentiated early- and late-season xylem, reflect annual growth in many temperate species. Across taxa, woodiness is not a single anatomical trait but a functional outcome of secondary growth. Gymnosperms generally produce softwood, consisting mainly of tracheids; angiosperms typically produce hardwood that includes vessels and fibers.

Woodiness has evolved repeatedly in plants and is often associated with a perennial, self-supporting life history. Some species remain herbaceous or become lianas or vines, retaining limited woody tissue or only seasonal lignification. Ecologically, woodiness supports vertical structure in forests, enables ongoing water transport under negative pressure, and contributes to long-term carbon storage in woody biomass. Human use centers on timber, pulp, and fuel, with properties varying by species, growth conditions, and age. The degree of woodiness ranges from herbaceous stems with minimal lignification to durable heartwood that persists for decades or centuries.