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Everything You Need to Know About Bearded Iris

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Everything You Need to Know About Bearded Iris

June 5, 2018

After 13 years as head gardener of England’s world-famous gardens at Sissinghurst Castle, Sarah Cook may have been forgiven for putting her feet up when she retired to the beautiful Suffolk countryside. But instead of twiddling her thumbs, she has been on a 14-year odyssey to rediscover and collect Cedric Morris’s bearded iris. The Suffolk-based artist and plantsman introduced and named around 90 varieties during the 1940s and 50s that caused a stir at Chelsea and have a painterly beauty all their own.

In her idyllic garden, the Cedric Morris blooms have their own patch while in another vast bed there are hundreds of other bearded iris all being carefully watched over. She shared her top five expert tips on how to nurture these elegant and statuesque beauties.

Photography by Clare Coulson.

1. Lighten up your soil.

Sarah Cook&#8
Above: Sarah Cook’s irises flourish in a gorgeous cottage garden (complete with a nuttery, an orchard, and picturesque sheep hurdle fencing).

Irises need to be grown on well-drained soil and tend to flourish in areas with lower rainfall. But if you have heavier soil, all is not lost. Sarah makes her beds slightly mounded to help drainage and also adds some grit. Most important, make sure that the rhizome is at ground level (often you may even see a happy rhizome above the soil). If this part of the plant is submerged and sitting in damp soil in winter, it may rot.

2. Choose good neighbors (or preferably none at all)

 Sarah Cook first got to know these bearded irises when she discovered Iris ‘Benton Nigel’—which has a rich blue color—growing at Sissinghurst. “They have a wonderful collection of old irises there and I’ve always found them more elegant than the modern ones,&#8
Above: Sarah Cook first got to know these bearded irises when she discovered Iris ‘Benton Nigel’—which has a rich blue color—growing at Sissinghurst. “They have a wonderful collection of old irises there and I’ve always found them more elegant than the modern ones,” she explains. “My eye is at that period of garden. I always think it’s quite important to have a plant of the right period for the house.”

Irises do not like competition, which is why they are often grown in a separate beds or up against a sunny wall. They will not flourish in crowded herbaceous borders where neighboring plants will shade the sun. “They won’t flower if they are in a poor position and eventually they will die from the competition,” adds Sarah.

3. Divide every four or five years.

 On her quest to find the missing irises, Sarah Cook went to botanic gardens, searched specialist iris catalogs, and visited private gardens (her mother introduced her to Hadleigh locals who had known Morris too); in  she staged a fantastic exhibit at Chelsea. She now has around  named varieties—and many more of what she calls &#8
Above: On her quest to find the missing irises, Sarah Cook went to botanic gardens, searched specialist iris catalogs, and visited private gardens (her mother introduced her to Hadleigh locals who had known Morris too); in 2015 she staged a fantastic exhibit at Chelsea. She now has around 26 named varieties—and many more of what she calls “second division” varieties (ones that Morris had possibly grown but not registered).

As a plant’s rhizomes multiply and form congested clumps, an iris eventually will stop producing flowers. Carefully dig up the whole plant and break up each chunk of the rhizome. These can then be replanted (each rhizome creates a new plant) and the leaves can then be trimmed back to a neat fan shape. This is best done in July. Some smaller rhizomes may not form new plants in the following year; they may need longer to settle in. For this reason, Sarah advises planting some of the chunkier rhizomes close to some smaller divisions to ensure you always have flowers.

4. Don’t forget to feed.

Iris &#8
Above: Iris ‘Benton Nutkin.’ Cook is still on the trail, but she’s now working within Plant Heritage to gather together all the pre-1940s British irises too, an endeavor she is passionate about.

Irises may be happy on light sun-baked soils, but don’t neglect them. “They are quite hungry. They like being fed,” says Cook, who gives them her own custom mix of Grow More with extra sulphate of potash and some kieserite for extra magnesium (a mix she used on the roses in her time at Sissinghurst) around March and then again in July when they are putting on their root growth. And water in irises that have just been planted or newly established plants if there’s no rain.

5. Keep them tidy.

 If you want to neaten up the flower stems, remove spent blooms by snapping them off the stem. But make sure there’s not another smaller bud beneath them. You can also cut off sections of stem to neaten up the plant.
Above: If you want to neaten up the flower stems, remove spent blooms by snapping them off the stem. But make sure there’s not another smaller bud beneath them. You can also cut off sections of stem to neaten up the plant.

When a plant has entirely finished flowering, Sarah advises neatly snapping off the entire stem directly from the rhizome—pull the stem forward to make a neat cut that will help prevent rot or virus. If the leaves look unsightly, then cut them back to a short fan and the plant will quickly make new foliage.

See more growing and care tips at Iris: A Field Guide to Planting, Care & Design in our curated guides to Perennials 101 and Bulbs & Tubers 101. Read more:

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