Iris, a genus of the Iridaceae family, evolved in the northern hemisphere in a wide range of soils and climates, from Europe, Middle East, and Asia to Northern America with around 280 species. With such variety, there are Iris suited to all garden types, locations and climate conditions. Most Iris grown in home gardens are cultivars of a just a few of these species and subspecies, but there are thousands of hybrids. Lesser known Iris species are also grown and studied by enthusiasts and collectors.
Bearded Iris, so named because of of the thick hairs that grow from the throat of the flower are the most commonly grown garden Iris, with the largest number of cultivated varieties. There are a dazzling array of hybrids available, from the simpler form, referred to as ‘historic’ Iris to the ‘modern’ cultivars. Bearded Iris cultivars are classified by height:
- Miniature dwarf under 20cm (MDB)
- Standard dwarf 20-38cm (SDB)
- Intermediate 38-71cm (IB)
- Miniature Tall Bearded 38-71cm (MTB)
- Border 38-71cm (BB)
- Tall 71cm+ (TB)
Bearded Iris need a sunny, well drained position, with cool to cold winters. They prefer neutral to slightly alkaline soil. Known for their drought tolerance bearded Iris only need moderate watering. Excessive water can cause rhizome rot. For this reason mulch should be avoided and they should be planted with the upper part of the rhizome at or above soil level. They are evergreen, but spent flowering stems and damaged leaves should be removed. Each rhizome will flower once, (with the exception of rebloomers) then put its energy into producing more rhizome offshoots, eventually making a clump which can be left or divided. So plant with room for the clump to expand. Feed in Autumn and early Spring with a low nitrogen fertiliser.
Aril and Arilbred Iris
These are some of the most extravagantly coloured flowers in the plant world, prized by collectors. The best show the following characteristics: the Aril ‘Spot’, a large deep black or dark signal in the middle of the fall, the aril shape with elongated upright standards and curled pendant falls, exotic veins and streaks in all parts of the flowers, unusual colours and combinations, extremely rich colours and some with large hairy beards. They prefer totally dry, hot baking summers, but can tolerate some wetness. In winter they will rot if they get too much rain. Arilbred Iris are Arils crossed with the more familiar bearded iris and these are less demanding to grow while still as rewarding with their spectacular blooms.
There are many more beardless Iris (apogon) species than bearded, and they are suited to a range of conditions, so that it’s possible to find a beardless Iris for nearly any place in the garden.
Ensata (Japanese Iris)
Descended from their species ancestor I laevigata, ensata hybrids have been carefully cultivated in Japan for hundreds of years. They range in form from elegant 3 falls(petals) to complex structures with up to 12 falls. All patterns are ‘acceptable’ but the effect must be harmonious. They need moisture and nutrient rich, mildly acid conditions. Ensata are dormant in winter. Suitable for pots, garden beds and pond edges. They bloom after the bearded Iris and can be enjoyed in pots or in drifts.
From Southern parts of USA these evergreen, colourful Iris need moisture, sun and warmth. They are low maintenance with attractive foliage all year round. Louisianas grow particularly well in frost free areas of eastern NSW. They do well in pots as long as moisture is maintained, such as standing in water, as well as garden cultivation in moist areas. They are happy growing in or beside ponds, and are heavy feeders preferring slightly acid soil.
Pacific Coast Iris (Californian)
Native to Oregon, Washington and Northern California, they grow in mostly mountainous areas near forest edges. While not the easiest Iris to grow PCIs are immensely rewarding if you can provide the right conditions. Most of them need acidic soil and prefer winter and spring rain and dryish summers. They can make excellent ground covers and can be grown in pots. The exquisite colours and patterns of the hybrids befit the term ‘jewels’, used to describe these diminutive Iris.
Crested Iris are also known as Evansia Iris. The majority originated from China and Japan, with a few from United States. Different to other members of the Iris family, with crests instead of beards, many suit semi shaded areas, under trees and shrubs and are referred to as woodland Iris. Crested Iris produce broad leaves that are arching or floppy. Flower stems are usually segmented with each segment producing a flower stem and further leaves. Most commonly grown are Iris japonica cultivars and the taller Iris wattii. The blue (and occasionally) white flowering Iris tectorum, common name Japanese roof Iris are also a delight.
Spuria Iris Originating in the Mediterranean area of Europe Spuria are among the tallest Iris. They bloom after the tall bearded Iris and grow best where summers are dry. Plant with room for the clump to increase, such as the back of a border – as they do not like to be moved – and they will make a spectacular display.
Most commonly grown in this group are the reticulata Iris, small gems which flower in late winter and are suitable for pots and rock gardens and the spring flowering ‘Dutch’ Iris ubiquitous in florist shops, and equally striking in pots and gardens, and of course vases. Plant bulbs in autumn. Feeding with bonemeal or fertiliser high in potash after flowering has finished will help the parent bulb and its offsets for the following season.