Phormium cookianum

A medium-sized native evergreen, clump-forming, arching perennial growing to around 1.5m tall with flower spike and 1m wide.

This large perennial produces wide strap-shaped, bright green leaves up to 1.5m long. Cylindrical yellow-orange flowers are produced in summer on tall stems ranging from 60cm to 1.5m in length.

Once established flax are tolerant of a wide range of conditions including windy coastal situations. They will also tolerate both dry and wet but don’t do well in full shade so would prefer full sun. They are also frost hardy.

Always choose healthy, well-grown, plants and plant after autumn rains, when the soil is moist and warm allows plants to establish a good root system well before summer. Planting is often improved on clay soils by adding extra topsoil and forming raised beds. Incorporate coarse sand, bark, peat, compost or other organic material to improve soil structure. Before planting, ensure the root ball is saturated and remove the planter bag or pot with minimal root disturbance. Trim any broken roots or damaged leaves off and plant at the same level as in the container. Dig a hole twice the diameter of the root ball to plant in. Long term slow-release fertilisers may be added at this stage. As soil is placed in the prepared hole tread firmly to bring soil in close contact with the root-ball. Unless the soil is very wet, water thoroughly making sure that moisture penetrates to the depth of the root-ball. Mulch with an organic mulch to help suppress weeds and retain moisture.

Apply an organic mulch annually to help suppress weeds and conserve moisture. Feed annually in spring with a balanced fertiliser such as blood and bone at a handful per square metre in spring as new growth begins. Divide and replant to revitalise plants that have started to look barren in the centre, if they start to get loose in the ground or if coloured plants start and revert back to plain green, then the green growth can be removed. This can be done in autumn to early winter and enables the new plants to establish while the soil remains relatively warm then plants can then burst into life the following spring. Dividing can be achieved by lifting the whole clump or digging pieces off from around the edge of the clump. Placing two garden forks back to back in the middle of the clump and then pushing in and forcing apart with the forks can be easiest. The resulting clumps can then be divided further either with forks or by hand. Cultivars are often best divided into clumps. The clumps should then be immediately re-planted in their new positions and watered in. People often divide clumps into fans, which is just one portion of the plant rather than a large section. This can be done also, plus you get far more plants this way but they just take longer to get to larger plants. Some people also like to trim the leaves diagonally. This helps with the establishment of the new plants as then the plants put more energy into root growth rather than leaf growth.

The rich nectar produced by the flowers is loved by tui and bellbirds.

Mealybugs can be a problem with flax. They tend to make their home in the bottom of the leaves/fans. They get in between the basal leaves. They are tricky to eradicate but large numbers on small plants can have a detrimental effect. They can be carefully cleaned off with a cotton bud dipped in meths.

Threatened Native Plant Garden

The best way to tell the difference between P. cookianum and P. texax isn't just by the size of the plants but by its flowers. P. tenax holds its flowers and seed held up tall and straight, whereas P. cookianum the flowers are drooping on the stem and the seed capsules droop and are twisted.

Maori used this flax as well as Phormium tenax for weaving into household items and clothing. They recognised some cultivars in particular for their fibre quality and strength.