Subshrubs

low-growing plants (5-60 cm tall) with lignified perennial, usually profusely branched shoots and no clearly expressed main trunk. Subshrubs often have a long rootstock (for example, bilberry and mountain cranberry); some have creeping shoots (cranberry). Sometimes, particularly in the high mountains, subshrubs assume a pulvinate form (Diapensia lap-ponica). The principal aboveground shoots live five to ten years. Subshrubs predominate in the vegetation cover of the tundras (species of birch and willow and many Ericaceae); they sometimes form a solid layer in coniferous forests. Subshrubs predominate in sphagnum marshes (cranberry, bog whortleberry, marsh andromeda, leatherleaf, and rhododendron) and form the vegetation of such wastelands as the heaths in Western Europe. They grow in the high mountains of South America, South Africa, and New Zealand, as well as in the Pamirs.

perennial plants in which the lower parts of the shoots bearing the renewal buds become woody and live for several years while the upper parts remain grassy and die each year (unlike in shrubs and undershrubs). Subshrubs are usually not more than 80 cm high; in rare cases they reach a height of 150–200 cm. They differ from perennial grasses in that their renewal buds are normally several centimeters above the ground. Subshrubs are found primarily in arid regions. The position of the buds above the ground protects them from overheating in the scorching soil. Examples of subshrubs are Ceratoides and many species of steppe and desert wormwoods, vetches, and saltworts (Halocnemum, Kalidium). An example of a particularly small subshrub is the creeping plant thyme.