Dianella

( dye - an - NELL - uh )

At-A-Glance Information

Commonly called Flax Lily, these perennial flowering plants need full sun in cooler climates and regular water. Their foliage is grass-like, and they have small blue flowers followed by shiny berries. These clump-forming plants are native to Africa, southeast Asia, the Pacific Islands, New Zealand, and Australia. Plants grow from underground rhizomes, and can have fleshy or fibrous roots. Take care when you are planting these flowers in your garden, as plant parts are potentially toxic to humans and pets if ingested.

Dianella Species and Varietals

The genus Dianella includes around forty distinct species and is a member of the plant family Asphodelaceae. Dianella grows best in USDA hardiness zones 5-8 or Sunset growing zones 8, 9 and 14-24. To find your zone, click here: Zone Map.

Dianella amoena (Matted Flax Lily)
Endemic to Australia, this endangered species of Dianella produces long grey-green strappy leaves and bluish-purple fragrant flowers in summertime that are considered large for the genus. These plants can form large colonies (over 16 feet wide) via underground spreading roots.

Dianella brevicaulis (Coast Flax-Lily, Coastal Flax-Lily)
This species has fibrous roots and produces purple flowers that bloom in summer. Leaves are green and form a tussock that reaches about a foot and a half tall at maturity. These plants prefer to grow in sandy soils in coastal and subcoastal locations, and are native to southern Australia.

Dianella brevipedunculata (Blue Flax Lily, Common Blue Flax Lily)
This hardy species reaches about a foot and a half tall at maturity, and produces purple-blue flowers followed by bright blue round berries that are mildly toxic. This species of Blue Flax Lily is native to eastern Australia, and can be an aggressive spreader in favorable, humid environments but is not considered invasive.

Dianella caerulea (Blue Flax Lily, Blueberry Lily, Paroo Lily)
This species is native to east Australia, and forms a mat of foliage 1-2 feet tall and 2-3 feet wide of shiny medium green leaves. Flowers can be either light or dark blue and have yellow stamen. They are followed by purple-blue berries. Varieties include 'Casitas Springs' (with grey-green foliage), 'Little Jess' (a compact variety) and 'Cassa Blue' (a dwarf of the species; to to 18 inches tall with soft, blue foliage).

Dianella longifolia (Blueberry Lily, Pale Flax Lily, Smooth Flax Lily, Blue Flax-Lily)
This species, native to Australia, produces a tussock up to 5 feet tall. Flowers are purple, blue, or whitish green in color, and foliage is green. Flowers bloom during the spring and summer months, followed by pale blue berries. These plants are highly adaptable, and can become weeds in disturbed areas.

Dianella nigra (Inkberry, New Zealand Blueberry, Tūrutu, New Zealand Flax Lily)
These plants are native to New Zealand, and produce purple flowers in spring and summertime in their native range. Berries that follow blooms are greyish-white to violet blue and glossy. Individual plants form clumps of foliage to between 16 and 24 inches tall and wide when mature.

Dianella revoluta (Black Anther Flax Lily, Blueberry Lily, Blue Flax-Lily)
This species, native to Tasmania and Australia produces tight clumps of foliage that spread via rhizomes. There are two common varieties: 'Baby Blue' (with green leave to 12-18 inches tall and pale purple blooms/green berries) and 'Little Rev' (to 2-3 feet tall, with yellow-green leaves - with blue-green undersides; though it rarely blooms).

Dianella sandwicensis ('Uki'uki, 'Uki, Hawaiian Lily, Hawaiian Dianella)
This species of Flax Lily is native to Hawai'i and New Caledonia. The berries from these plants have been used to create dyes for clothing and other textiles, and leaves were uses historically to thatch house walls. Leaves are green and strappy, a bit wider than those of many other species in this genus. Plants reach about a foot and a half tall at maturity, and have a spread of around 3 to 5 feet. Flowers are white to light blue and are followed by striking purple-blue shiny berries.

Dianella tasmanica (Tasman Flax Lily, Tasmanian Flax Lily, Flax Lily, Blue Berry Flax Lily)
This native of southeast Australia and Tasmania grows to 3-4 feet tall and spreads by rhizomes with age. Summer flowers are blue and are held in loose clusters and are followed by large blue berries. Varietals include 'Variegata' (with striped white leaves, pictured), 'Yellow Stripe' (with striped yellow leaves), and 'Tasred' (with green leaves that are red at the base).

Caring for Dianella

Take care when you are planting these flowers in your garden, as plant parts are potentially toxic to humans and pets if ingested. Flax lilies prefer to grow in full to partial shade. The warmer the climate, the more shade these plants will need. The less sun they get, however, the less they will flower. The best exposure is around 4 to 6 hours of direct sun each day, with shade during the hottest afternoon hours. Soil should be well-draining and moderately fertile. Flax Lilies prefer a pH between 6.0 and 7.5 (slightly acidic to neutral) and to have their roots in loamy or sandy soils, but can adapt to poor soils. If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Dianella can be planted either in-ground or in containers. Apply a thick layer of mulch around the base of plantings to increase soil moisture retention, maintain soil temperatures, and suppress weed growth.

Water newly planted Dianella regularly as they establish a strong root system. At maturity, these plants are considered to be somewhat drought-tolerant and will get by on rainwater alone with supplemental waterings during the warmest times of the year. Signs of overwatering include plants drooping or turning brown; if this occurs, cut back on irrigations. Each year in springtime, apply a 2-inch layer of organic compost around the planting area to improve soil structure, drainage, and nutrient load. This feeding should be sufficient to provide these flowers with enough nutrients to get through their growth and flowering seasons with ease. Pruning is not necessary, but if any foliage is becoming unsightly, it can be removed at any time during the growing season. Spent flowering stalks can be removed to neaten up the look of plants or to discourage pets or children from picking and eating the toxic berries that follow. If propagating these plants via seed, the flowering stalks will need to remain and berries will eventually mature, providing seeds for the next generation of plants. Dianellas will survive in the landscape for 10-15 years in the garden before needing to be replaced.

Propagation

Dianella can be propagated either by division or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the division method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Flax Lily plant, follow the instructions below:

Propagating Dianella by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seed heads on plants are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will continue to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
In either late winter or early springtime, get your container prepared. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 2-6 weeks from sowing.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 65 and 72 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Propagating Dianella by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil, compost and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring (after the plant has entered dormancy, but before it has begun its new spring growth), and needs to be done every few years (typically every 2-3 years) regardless of whether you have the goal of propagating the plants for best performance, especially if you are growing Dianella in containers. To propagate by division, follow these steps:

Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the root(s). Once you have worked it up out of the ground, lay it out.
Start to tease apart the roots with your fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick root section attached to shoots.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divisions and water thoroughly.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout in the next growing season.