Salix retusa aka Retuse Leaved Willow

Salix retusa, or notchleaf willow, is a low alpine shrub. It is deciduous, which means it sheds its leaves. It belongs to Salicaceae, the willow family. The RHS lists it as non-native to Britain and Ireland. Its stems creep along the ground to form a mat. They take root at nodes, the joints along each stem. This low growth suits groundcover use where plants need little height.

The two sources give different heights for this small willow. The RHS gives about 0.3 feet [0.1 metres] in height. Chicago Botanic Garden gives a height of 1 foot [0.3 metres]. The RHS gives a spread of 0.3–1.6 feet [0.1–0.5 metres]. Plants reach their full size in two to five years. The small green leaves have a glossy surface. Their shape ranges from oval to oblong. The leaves fall for winter and leave the creeping stems bare.

Small catkins, or flower clusters, stand upright as new leaves emerge. The RHS says these spring catkins have a silver colour. Chicago Botanic Garden lists white blooms from March to April. The flowers and fresh leaves form the spring display together. Its low growth makes it useful in rock gardens. The RHS also suggests banks, slopes, and informal gardens. Its list includes sites by the coast and wildlife gardens.

Grow this willow in full sun, as both sources advise. The RHS calls for deep, moist soil that drains well. The plant accepts clay, loam, or sand. It grows in acid, neutral, or alkaline soil. Even so, avoid thin soil that lies over chalk. Chicago Botanic Garden lists dry conditions for growth instead. These sources differ, so neither sets one clear need for water. The RHS accepts sites both with and without shelter. Its H7 rating shows hardiness below −4°F [−20°C]. Chicago lists USDA zones 3–7.

The RHS lists pests that may attack this species. Aphids and caterpillars are among the pests it names. Others include sawflies and willow leaf beetles. Willow scale insects may also occur on the plant. Diseases may include willow anthracnose, rust, and honey fungus. These risks do not mean that each plant will suffer. To make new plants, divide them or take cuttings. Take softwood cuttings in early summer, or hardwood cuttings in winter.