Iris - Tall Bearded
Bearded irises have one of the biggest ranges of flower hues of all plants - aptly enough, as they are named after Iris, the Greek goddess of the rainbow! Their spectacular, bold blooms in late spring offer wonderful potential for creating colour schemes in the garden. The epithet 'bearded' comes from the hairy tufts on their lower petals (called 'falls'). They derive from several Iris species, including Iris germanica, the old-fashioned purple or white 'flag iris' seen growing wild in abandoned country gardens, which starts flowering in winter in Sydney and continues on into spring.
They are grouped into categories according to height: dwarf, intermediate and tall. It is the tall ones (growing 70cm-1m tall) which are best suited to Sydney (as the others need frost in winter to do well) and even so, attention must be paid to their cultivation, because as they are Mediterranean in origin, our climate is on the edge of their adaptability. The best spot for them is in a sunny, dryish garden bed with very well-drained, alkaline soil. Rhizome rot is one of the biggest worries associated with these plants. Avoid the use of animal manure nearby to the irises, as this can cause rot, as can overwatering. The rhizome should not be buried deeply: its top should be at ground level with just a very light covering of soil (to prevent sunburn in summer) but should not be covered with mulch, and the plants should not be shaded by nearby foliage or weeds. Plant them about 30-50cm apart.
To keep the irises vigorous, dig them up and divide them every three or four years after flowering or in late summer, discarding old withered central rhizomes and replanting the healthy ones, preferably in a different position in the garden. Trim away two-thirds of the foliage, cutting about 15 cm above the rhizome - this will reduce transpiration and help the rhizome remain stable until new roots establish. Plant the rhizones about 30cm apart. Fertilise with a slow-release or organic plant food in winter and when replanting. Remove any diseased or brown leaves and dispose of in the green waste bin, not in the compost heap. Remove the flowering stems close to the ground after blooming is over to help protect the rhizome from rot.
Tall bearded irises are natural companions for other Mediterranean plants, such as perennial wallflower (Erysimum), Euphorbia, lavenders, Artemisia, statice (Limonium) and Dianthus, which all enjoy the same growing conditions and are in bloom at the same time. Irises are also often planted amongst roses and they can be grown in pots - in which case they should be divided every two years.
Whilst their flowers are stunning, the blooming season - usually in October - is relatively short (apart from Iris germanica mentioned above. There are some varieties (called the remontants) which rebloom in late summer or autumn, which have an added appeal. Many of these were raised in the USA in the 1920s and 1940s, and in recent times breeders have become interested in this characteristic again and have developed more of them. Some suitable ones for Sydney include 'Victoria Falls' (light blue), 'Cascade Pass' (white), 'Harvest of Memories' (clear yellow), 'Perfect Couple' (mauve, white) and 'Total Recall' (pale yellow). The flowering stems of irises can be picked for vases; some varieties are even perfumed!
There are a number of iris catalogues online, which can whet your appetite for adding a few new ones to your garden.
Flowers in June, July, August, September, October, November.