Australian flax (Dianella) and New Zealand flax (Phormium) are two plant genera within the Asphodelaceae family, often mistaken for each other due to their similar common names and ornamental use in landscapes. However, while they share many characteristics, they also possess distinct differences that make each unique.
1. Little Jess™ Dianella caerulea ‘DCMP01’.
2. Sweet Mist™ Phormium tenax ‘PHOS2’ PVR.
Taxonomy and Family
Both Dianella and Phormium belong to the Asphodelaceae family, which underlines their botanical kinship. This familial link points to some shared characteristics, such as their rosette habit arising from rhizomes, their robust nature and adaptability in various environmental conditions. Despite this connection, their genus differences give rise to varied aesthetic and functional attributes.
Growth Habits and Landscape Uses
In terms of growth habits, Dianella spp. and Phormium spp. display remarkable similarities. Both are evergreen, forming rosette clumps of sword-like foliage emerging from rhizomes that add structure and texture to gardens. Each leaf has a mid-vein that distinguishes them from other strappy plants when not in flower.
Their adaptability makes them excellent choices for a range of settings—from dry, sunlit areas to shaded, moist spots. Most prefer not to sit in wet feet for extended periods. These plants are renowned for their minimal maintenance requirements and resilience, thriving in diverse soil types and tolerating drought and coastal conditions effectively. As ornamental plants, they provide a year-round visual appeal, often used to create striking foliage contrasts in landscape design.
3. Tasred™ Dianella tasmanica ‘TR20’ PVR.
Flower Shapes and Differences
The primary difference between these two genera lies in their flowers. Dianella boasts small, star-shaped flowers that are typically blue or violet, perched on slender, wiry stems above the foliage. These are often followed by decorative berries, adding a subtle yet attractive element to the plant’s appearance.
In contrast, Phormium produces more robust flower spikes with tubular flowers, often in hues of red or yellow. These flowers mature into seed pods once pollinated.
So, if your flax plant has little star-shaped blue flowers or berries, it’s an Aussie native. But if it has yellow/orange tubular flowers or seed pods, it’s an NZ native. Also, Phormium spp. can grow a lot larger than Dianella spp., but there are many smaller Phormium that can be easily mistaken for Dianella.
Conclusion
While Australian flax (Dianella) and New Zealand flax (Phormium) share a family lineage and similar landscape uses, their distinction is most evident in their floral presentations. Both serve as versatile and hardy additions to gardens, offering structural interest and ease of care. Whichever option you choose, your garden will be more colourful and beneficial to native NZ wildlife!