Polygala myrtifolia aka Myrtle Leaf Milkwort

Polygala myrtifolia is a shrub that stays green all year. Its other name is myrtle-leaved milkwort. It belongs to Polygalaceae, the milkwort family. Its native range includes South Africa and Lesotho. Kew puts it in the subtropical climate group. It is not native to Britain or Ireland. Frost can harm its tender growth, which limits outdoor use.

This shrub grows upright, with a bushy shape and many branches. Its branches spread as well, so it widens with age. The leaves stay mid-green all year. Garden plants reach about 5–8 feet [1.5–2.5 metres] tall. They grow about as wide as they grow tall. Leave room for both height and width when planting. The RHS says plants reach full size in five to ten years. Flowers bloom from spring through summer and into autumn. They come in purple and greenish white, with pink veins. This long bloom time adds value to beds and borders.

Outdoors, choose full sun or part shade in a sheltered spot. The RHS lists sites that face east, south, or west. Use soil with a fair level of nutrients and much humus. Water must drain well, even when the soil stays moist. Chalk, loam, and sand all suit this plant. It grows in acid, neutral, and alkaline soil. The RHS gives it a hardiness rating of H2. It can cope with cold, but it cannot survive freezing. This rating covers a minimum temperature range of 1–5°C. You can also grow it in a greenhouse or conservatory.

Under glass, use peat-free potting compost and give it bright light. In this setting, shade it from hot sun. Give it plenty of water in the summer months. The RHS suggests it for city gardens and courtyards. It also suits flower beds and borders beside walls. Its leaves give cover after the flowers have gone. In spring, prune shoots that winter has harmed. Take softwood cuttings in early summer to grow more plants. You can also take semi-ripe cuttings from mid- to late summer.

Under glass, watch for aphids and whitefly. The RHS lists this plant as a high-risk host for Xylella fastidiosa. Keep this disease warning in mind, along with its need for frost protection.