Blue Flax Lily Dianella caerulea

Blue flax lily grows as a loose open fan of flat, soft, blue green leaves, and it travels quietly by underground rhizome rather than sitting as a tight clump. Its signature is the flowering: small blue stars on fine branching stems held well clear of the leaves through spring and summer, followed by berries in a glossy violet blue that birds work over. It is a native used mostly in numbers, mass planted under established trees where turf has given up and run along the front of native borders.

Where blue flax lily works, and where it does not

Dianella caerulea is one of the more adaptable natives on this list. It occurs naturally down the eastern seaboard, takes full sun through to fairly deep part shade, handles coastal sites and frost in most temperate districts, and once the roots are down it wants little water. Soil is not fussy so long as it is not permanently boggy. It also copes with root competition better than most border plants, which is why it holds on under gums. Plant it in drifts rather than singles, roughly three to five plants a square metre depending on how fast you want cover, and mulch between them for the first year while the rhizomes knit. The failure mode is not cultural, it is specification. This plant is often ordered when Lomandra was intended, and the two do not behave the same way. Dianella spreads sideways underground and the leaves sit in a soft open fan, so it fills a wide drifted border well but slowly blurs a single clipped row against a path or driveway, where a mat rush would hold the line for years. Use it where spread is an asset: broad borders, wide beds, batters, understorey and swale edges.

Dianella against the other strappy plants here

The obvious comparison in this range is Phormium Bronze Warrior. Both are evergreen and strappy, but that is where it ends. The phormium is stiff, broad leaved, bronze to purple black, and stays as one big architectural clump you plant singly or in threes as a feature. Dianella is soft, blue green, low and spreading, and does its work in dozens. Pick the phormium for a statement and Dianella for coverage. Both sit on low water once established, so they can share a bed without one dragging the irrigation up. In deep dry shade under a canopy neither is ideal, and Silver Lady is worth considering if you can water it. More of the range sits under flax lily.

Cutting back and feeding a flax lily planting

There is really one maintenance job. Every second or third year the clumps tire, fill with dead leaf and look tatty, and the fix is to cut the whole planting back hard in late winter, close to the base, so it flushes clean with the spring growth. Do the lot at once rather than plant by plant, or the bed looks patchy for months. Seed heads can be sheared off after berrying if you do not want self sown seedlings, and note that seedlings of the straight species vary in leaf width and colour. Feeding is light: a native safe, low phosphorus fertiliser once in early spring is enough, and overfeeding only makes soft floppy leaves.

Choosing a size

This plant is available in 3 sizes, from 125mm up to 200mm, priced from $16.95 to $29.95 per plant. The size shown is the pot the plant arrives in, which is the rootball, not the height of the plant. These are younger plants, priced for planting in quantity, and they establish quickly once in the ground. Not sure which to choose? Read our guide to low water gardens.