As I write this my garden is in an iris frenzy. There are bearded irises in the Dry and Jewel Gardens, flag irises rising out of the water of the pond and Iris sibirica in great clumps, also in the Jewel Garden.
As I write this my garden is in an iris frenzy. There are bearded irises in the Dry and Jewel Gardens, flag irises rising out of the water of the pond and Iris sibirica in great clumps, also in the Jewel Garden.
With their intense colours and gorgeously rich petals, they are all the most sumptuous of flowers.
The bearded irises have the greatest range of colours of almost any flower available to the gardener, from a purple – like that of ‘Dusky Dancer’ – that’s so inky dark it’s almost black, to pure white via every blue, mauve, pink, burgundy, orange and some voluptuous, velvety browns. The only shade missing from their palette is crimson.
The petals are frilled and ruffled and carried on strong, straight stems up to 1.2m tall and accompanied by sculptural upright spears of glaucous foliage fanning out from the rhizome. Everything about them is upright and dramatic.
Bearded irises grow from rhizomes that look like ginger and sit on top of the soil – the roots grow down from these.
When planting, it’s very important to leave the rhizomes on the surface so they can become baked by the sun, with just the roots underground. It is the intensity of the baking the rhizomes get in July and August that’ ll determine the quantity and quality of flowers the next May and June – hence the need for the sunniest spot possible.
The best time to buy and plant irises is between the middle of summer and early autumn. If, like me, you live in a wet area and also have clay soil then it is a good idea to plant them on a little mound with lots of added grit beneath them. They really do like good drainage as well as baking sun in order to perform their best.
Every three or four years it is advisable to dig up a clump of rhizome after flowering and cut it into sections, ensuring each section has a visible bud. Replant these new divisions to make three or four new clumps planted 15-30cm apart.
It is best to throw away the oldest part of the rhizome, which will have lost its vigour. Trim the leaves by half to stop them rocking in the wind before the roots have had a chance to anchor them firmly.
The opposite, in growing conditions at least, are the flag irises, Iris pseudacorus, which are happiest in a bog or in the muddy shallows of a pond. They can become a thicket so I divide mine every few years, breaking or cutting up the clumps and replanting at wider spacing.
Iris versicolor, from North America, is also very happy in these boggy conditions but will grow in a border with rich soil. The Japanese iris, Iris laevigata, is bright blue and is best grown submerged in shallow water. There is also a white variety, I. laevigata ‘Alba’ .
Last but by no means least in the roster of irises in my own garden is Iris sibirica, which has small blue flowers tinged with mauve and yellow and orange ‘tiger’ stripes on the outer sepals. It has a freshness and clarity that few other flowers of any sort ever achieve. It will grow both in the damp margins of a pond and quite happily in a border as long as the soil is not too light and has plenty of organic matter added to it.
The foliage is much slimmer and floppier than that of bearded irises and they do need supporting. It is available in other colours, such as the amethyst ‘Ruffled Velvet’ and the reddish-purple ‘Showdown’ . But it is the clear blue that I love the best.
The clumps grow outwards and tend to thin out in the centre, so it is a good idea to lift the whole lot every few years, divide them up and replant in a number of new groups, which will then grow all the more vigorously.
