How to win over your iris

With sunshine and good drainage, you can grow bearded iris in the most unpromising of soils

I'd be prepared to go overboard for big bearded iris if only they would show a few more signs of being interested in me. I've been let down too often to want to go through the whole humiliating process of rejection again.

At least, that's how I felt until last week when, on my way back from the Courson flower show, I called in briefly at Monet's garden at Giverny. There, the bearded iris were looking so fabulously handsome, set in strong, long lines down the edges of the narrow beds that I was hooked all over again.

The Giverny beds are heaped up into long mounds, like asparagus beds, and the garden is open and unshaded. This is what the bearded iris like: good drainage at the roots and plenty of sun to ripen the rhizomes. My garden, being predominantly shady and made on very heavy clay, is not the most propitious place to grow them. But we recently cleared a new area of the bank, not overhung by trees. Being on a steepish slope, it is well drained. Tulips have flourished there as nowhere else in the garden, and I have hopes that bearded iris will, too. I am planning a trip to Croftway's nursery in Bognor Regis to choose plants from the 22,000 they have growing in their iris fields.

Their catalogue distinguishes between the modern bearded, mostly American cultivars and what Tom and Graham Spencer of Croftway's call the "classic" bearded iris, with flowers that are less ruffled (or muddled, depending on your point of view) although no less complex in their colouring.

The Spencers are very keen on the Intermediate bearded iris, shorter and earlier into flower than the tall bearded, but there is plenty else going on in our garden. I want a grand slam in June so will choose from among the tall bearded iris, all more than 28 inches high. The Intermediates can be anything from 16-27 inches tall, the dwarfs, which flower during April and May, hover around the 15 inch mark.

If you have chosen the right place to plant them, bearded iris will need little attention, although an annual sprinkling of bone meal or hoof and horn does wonders for flowering. Avoid feeding bearded iris on fertilisers which are heavy in nitrogen. This makes the leaves too lush and so more prone to disease.

Keep the rhizomes free from weeds and cut down the flower spikes when the flowers themselves have finished. If the clumps do well, they may need splitting and replanting after four or five years. If their flower power does not seem to be fading, then leave them alone.

The best time to split them is immediately after they have finished flowering. Lift the whole clump, refresh the soil with bonemeal and split off the most vigorous portions of the old clump, each with a section of rhizome and a good strong fan of leaves. Trim the leaves down to half their length and replant the iris about 15 inches apart.

The worst disease bearded iris get is a rusty kind of leaf spot. This usually appears just after the flowers have come out. You see small, round greyish-brown spots on the leaves and they spread at an alarming rate. First the tips of the leaves wither, then the entire leaf collapses. Spraying with fungicide helps but the most effective one (Benlate) was withdrawn from the retail market last year. Gardening Which? suggests as a substitute either Nimrod-T (Zeneca) or Tumbleblite (Murphy). A commercial grower tells me that a weak solution of bleach doesn't come amiss, but current legislation forbids recommending such simple remedies. Meanwhile, if you see Benlate still on sale, grab it.

If you spray, you need to start before the iris come into flower and repeat the treatment every 10-14 days. The best solution of all, of course, would be for breeders to concentrate a little less on adding ruffles to the flowers and a little more on producing strong, disease-resistant stock.

The Spencers grow on clay which sounds as unpromising as mine, but they have found that ridging up the soil in their fields, even by as little as three inches, improves drainage enormously. Grit helps too, if you can work it in underneath the iris roots when you plant. If you can't make any kind of raised bed, then the safest way to plant on heavy soils is on a slight mound.

Make a shallow, dish-shaped hole and build a little heap of soil in the centre. Set the rhizome on top of the heap and spread its roots out horizontally on both sides. Cover the roots with soil, leaving the rhizome itself slightly exposed. If you are planting in summer, the iris will need watering in. Otherwise they won't need watering at all, which is a great advantage.

Around 200 species of iris grow wild between the Arctic circle and the tropics. There aren't any in the southern hemisphere. Bearded iris though are unlikely to be happy north of York. The beardless sibiricas are a better bet there. For the bearded iris, alkaline soil is better than acid, though some of the Japanese species such as Iris confusa like slightly acid conditions.

Iris confusa is said to be tender, but I picked up a plant last summer, attracted by the handsome foliage, put it in a pot filled with ericaceous compost and it came through last winter completely unscathed. Since we lost more plants last winter - hebes, ceanothus and cistus - than ever before, this is a puzzle.

It is flowering now, looking more like an orchid than an iris, with delicate white flowers speckled with lilac and yellow. They are quite small, with standards much less important than the wavy falls. The foliage that intrigued me is held on top of strong rigid stems about a foot tall, so the effect is of a palm, rather than an iris. Most iris have leaves that spring straight from the ground. Iris japonica has similar orchid like flowers, slightly larger than those of my Iris confusa but the foliage is not so striking.

At Giverny, the irises bordered narrow beds filled with lamb's ear, forget- me-not, purple tulips, mauve sweet rocket, tall wobbly alliums, dark purple wallflowers, aubrieta and opium poppies. They thrive, because they are on the edge of the beds where the foliage of the other plants does not flop over them too much. They are not good sharers. If you plant them in mixed beds or borders, keep them to the front, so that the rhizomes are open to light and sun.

Bearded iris are available from Croftway Nursery, Yapton Rd, Barnham, Bognor Regis, West Sussex PO22 0BH (01243-552121). The nursery is open every day from 9am-5.30pm. They will also be at the South of England Show, Ardingly, Haywards Heath from 6-8 June, at Jardinage, Chelsea Town Hall, Kings Road, London SW3 on 20 June and at the Gilbert White Museum Unusual Plants Fair at Selborne, Alton, Hampshire on 22-23 June. Plants can be sent mail order during August and September.

For more information on iris try and track down Brian Mathew's The Iris published by Batsford in 1981. Join the British Iris Society, c/o The Secretary, The Old Mill House, Shurton, Stogursey, Somerset TA5 1QG (Subscription pounds 9 per annum). See the national collection of bearded iris at Myddleton House Garden, Bulls Cross, Enfield, Middlesex EN2 9HG (01992-717711).