Blue flax lily

Sun

Full sun to partial shade; afternoon shade helps in hot, dry inland gardens.

Water

Water regularly while establishing. Established plants tolerate dry spells, but grow better with occasional deep watering during prolonged drought.

Soil

Well-drained sandy, loamy or clay soil; avoid ground that stays waterlogged, especially in winter.

Height

1.5-4 ft (0.45-1.2 m), depending on the form and growing conditions

Spread

1.5-3 ft (0.45-0.9 m), gradually widening through rhizomes

Flowers

Spring to summer; small blue to violet-blue flowers with conspicuous yellow anthers, followed by blue berries.

Foliage

Evergreen. Tough, narrow, green strap-shaped leaves arising in fans; leaf width and plant size vary considerably within the species.

Growth

Moderate

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Heat tolerant
• Wildlife
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.6 ft (0.47 m)

3. After 2 years

   2.1 ft (0.65 m)

4. After 3 years

   2.7 ft (0.83 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Mildly toxic: may upset a stomach

Native to

Australia

Growth rate

Moderate

• Water deeply during the first growing season, allowing the soil surface to dry between waterings.
• Keep the crown at soil level and avoid planting in poorly drained hollows.
• Apply a light dressing of balanced, slow-release fertiliser in spring if growth is weak; avoid heavy feeding.
• Mulch around the clump, leaving the crown clear.
• Divide crowded clumps in spring and water the divisions until new growth appears.
• Move container plants to a bright, frost-free place where winters are too cold.

Pruning. In late winter or early spring, cut dead and badly damaged leaves individually at the base without cutting into the crown. Remove spent flower stems after the berries finish, or earlier if you do not want seedlings.

Spring

Plant or divide clumps once the risk of hard frost has passed.

Spring

Remove winter-damaged leaves and feed lightly if needed.

Summer

Water new plants regularly and established clumps during prolonged dry weather.

Late summer

Leave berries for display and birds, or remove fruiting stems to limit seedlings.

Autumn

Move pots under cover before freezing weather in colder regions.

Winter

Keep sheltered pots barely moist and check that outdoor crowns are not sitting in wet soil.

• Plant repeated clumps along paths for a loose, evergreen edge.
• Use beneath open-canopied trees where its upright leaves contrast with softer groundcovers.
• Combine with lomandra, small grevilleas and other Australian plants in informal borders.
• Grow in containers beside a sheltered entrance or courtyard.
• Mass on well-drained banks for year-round foliage and seasonal blue fruit.

Garden styles it suits: Australian native, Modern, Architectural minimal, Coastal, Low-maintenance and Wildlife garden.

Plant it with: Lomandra, Kangaroo paw, Westringia, Dwarf grevillea, Coral bells and Cast-iron plant.

Wildlife: Flowers provide pollen for bees, and birds may eat the berries. Dense established clumps provide shelter for small garden animals.

• Root or crown rot in waterlogged soil: improve drainage, reduce watering and replace badly rotted plants.
• Rust or fungal leaf spotting: remove affected leaves, improve air circulation and water at soil level.
• Scale insects: inspect leaf bases and undersides; remove small infestations by hand or use a labelled horticultural oil.
• Brown or frost-damaged foliage: shelter from severe cold and drying winds, then remove damaged leaves when spring growth begins.

Reports about the edibility of Dianella berries conflict, and species are easily confused. Treat the berries as potentially harmful rather than edible; ingestion may cause digestive upset. Reliable species-specific evidence for poisoning in cats, dogs and horses is limited, so keep pets and livestock from eating the plant. Seek medical or veterinary advice after a significant ingestion or if symptoms develop.

• Tasman flax lily (Dianella tasmanica)

  Usually has broader, more arching leaves with conspicuously toothed margins. Blue flax lily generally has narrower, more upright leaves, although forms vary.

• Spiny-headed mat-rush (Lomandra longifolia)

  Has dense clusters of small cream flowers rather than open sprays of blue flowers, and does not produce glossy blue berries.

• Mondo grass (Ophiopogon japonicus)

  Usually makes much lower, fine-leaved tufts, with short flower stalks tucked among the leaves rather than taller, branching flower sprays.

Dianella is a diminutive of Diana, the Roman goddess, while caerulea means blue, referring to the flowers.

Propagation. Divide established clumps in spring, keeping roots and several healthy leaf fans on each division. Seed can also be sown after cleaning away the fruit pulp, but germination may be slow and seedlings can vary.

Accepted botanical name

Dianella caerulea

In the US and Canada

Introduced in the lower 48 states.

Native range

New Guinea, New South Wales and Queensland.

Measured

Average height 50 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.