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Best uses

An effective landscaping plant that is attractive even not in bloom. Will tolerate sun, shade and dry conditions, making it great for underplanting under trees and shrubs. Can be used in containers and in mixed beds and borders.

Physical characteristics

This evergreen iris produces large, lush fans around 50cm tall, with a flower spike reaching up to 2m. The plants multiply rapidly so clumps can easily reach 1m across.

Flowers and foliage

This iris produces delicate frilled flowers that have a clear lavender hue and bloom from October to December. Every flowering stem of the plant is branched and each of them may bear as many as 50 blooms over a period of 8 to 10 weeks. The flowering stem can reach up to 1m tall. The leaves are a lush vibrant green and sword shaped.

Preferred site

Prefers moist soil in partial to full shade. Plants will cope with dry conditions. However, they will do better if they are given some moisture (although too much will cause them to rot). When grown in places with warmer conditions, evergreen Evansia irises continue to grow almost throughout the year and go into the dormant phase only for a short period. They will tolerate very light frost but this will the damage flowers.

Preparation for planting

Plant when the soil is moist and warm in autumn or early spring so that a good root system develops to support vigorous new growth. Remove all perennial weeds. Incorporate bark compost or other organic material. Before planting, ensure the root ball is saturated and remove the planter pot with minimal root disturbance. Trim any broken roots and plant at the same level as in the container. Dig a hole twice the diameter of the root ball, press in and water once planted. Make sure plants are watered well until established if planting in a drier period. Plant with some general slow release fertiliser and then every spring apply an organic fertiliser (such as blood and bone) at a handful per square metre as new growth appears. Do not apply lime, as iris prefer the soil to be more acidic.

Planting too closely leads to spindly growth, poor flowering and eventual decline. In a well-planned border, flowering plants should just touch each other to create a full effect without overcrowding. Plant approximately 60cm apart.

Maintenance tips

Apply mulch annually to suppress weeds and conserve moisture. Groom plants occasionally during the summer by removing spent flower stalks and dead leaves. Apply organic fertiliser in spring at a handful per square metre or less. Too much fertiliser may result in leafy growth at the expense of flowers.

Plants may be left undisturbed for four to five years before lifting, dividing and replanting. This can be achieved by lifting the plants, putting two garden forks back-to-back through the clump and pushing apart. The resulting clumps should be immediately replanted where they are to flower. If they are left for several years without being divided, they do not perform as well. Dividing not only gives you more plants, but it also rejuvenates them. Do not disturb plants if they are healthy and flowering well.

You can also propagate Iris wattii from stem cuttings. Take a piece of long stem and cut off the main plant using a sharp knife or secateurs. The piece of stem can then be stood in a glass/pot of water for one to two weeks. You will soon notice new roots emerging from joints of the pieces. These can then be potted up or planted out in the garden. As plants of this iris species do not live for long, it is advisable that you grow new plants every few years.

Some iris growers suggest that the flowering stems of Iris wattii should be staked as soon as they start to flower at the onset of spring. This will not only help to maintain the shape of the clump but also stop them from bending due to their own weight. This makes sense when you see that the flowering spray may sometimes be as tall as 2m tall.

Pests and diseases

Generally pest and disease free.

Companion and combination plants

Plant under trees and shrubs to create winter interest and brighten dark areas.

Location at Auckland Botanic Gardens

Urban Trees

Interesting facts and tips

This plant is one of the crested (or Evansia) types of Iris so-called because they have a 'crest' or ridge on their three larger outer petals instead of a 'beard'. Many of these crested types come from Japan and China.