Dianella caerulea aka Blue Flax Lily

Dianella caerulea is an evergreen perennial in the Asphodelaceae family. Its common names include flax lily and paroo lily. It comes from southern New Guinea and eastern Australia. Its range extends south to Tasmania. Wild plants grow near creeks, on heath, and in open woods. These sites often have sandy soil. The species varies in size across its wide range.

Plants form leafy clumps that grow from underground rhizomes. The many narrow leaves give them a grass-like look. The RHS describes plants about 1.6–2 feet (0.5–0.6 m) tall. Its broader garden range reaches 3.3 feet (1 m). Spread reaches about 1.6 feet (0.5 m). Useful Tropical Plants records extremes of 6.6 feet (2 m). Those taller plants fall outside the usual garden range. The leaves stay green through the year.

Pale blue flowers appear in summer above the leafy growth. They grow in panicles with short side branches. Glossy, rich blue berries follow the blooms. Reports put fruit width at about 0.05 feet (0.015 m). The leaves and fruit give the plant much of its garden value. It suits beds, borders, pots, and sheltered courtyard gardens. The RHS also lists coastal and informal garden settings. Plants reach their mature size in two to five years.

Choose a sheltered spot with sun or partial shade. Grow it in soil that drains well but contains humus. Moderately fertile loam or sand suits its needs. It prefers acid to neutral soil. The RHS gives it a UK hardiness rating of H3. This limits outdoor use to mild or coastal UK sites. Plants For A Future lists USDA zones 8–11. Cold tolerance varies, and some forms withstand brief frost or snow. Long spells well below freezing do not suit it.

The RHS reports few usual pest or disease problems. Plants need no routine pruning. Sow seed in spring, or divide the rhizomes in mid-spring. The leaves yield strong fibre and provide material for baskets. Food safety accounts conflict and need care. Plants For A Future and Useful Tropical Plants describe edible fruit. They report eating it either raw or cooked. The RHS warns against eating the fruit and flags risks to pets. Treat the berries as ornamental rather than food. Plants For A Future lists no known medicinal use.