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Cultivating a rainbow: bearded irises care guide

Cultivating a rainbow: bearded irises care guide


Much loved by artists, especially Vincent van Gogh, bearded irises are an absolute must have in a spring and early summer garden. The Dutch artist was a serial iris painter and we can understand why. These blooming lovelies, with shades across almost the entire colour palette – including blue, a most uncommon hue in flowers - make the most fantastic impact when in full bloom. You’re bound to find several that will complement any colour scheme you wish to achieve in your backyard – or container garden. These stately, elegant plants also come in a range of heights and can be used to advantage as a great accent when mass planted, or nestled happily in cottage-style planting. Even when they’re not flowering, their dramatic sculptured sword-shaped leaves add interest to the garden year round.

Being rhizomes, they are one of the most reliable of flowering bulbs and flourish in almost any garden worldwide. So with the great conditions we have in most regions of South Africa, you shouldn’t have any problem with growing them. They are one of the easiest plants to cultivate, making them perfect for beginner gardeners.

If you want to get the best out of them in your garden, all you need to do is consult this care guide.

The best position and soil for bearded irises

They can be planted out at any time of the year, but preferably not in full midsummer heat! Bearded irises on the whole prefer a full sun position to bloom at their best, although they will handle light shade as long as there’s dappled sunlight for at least five to six hours during the day. If you live in an extremely hot region, they will need some shade in the afternoon. One thing they do need is friable, well-draining soil, so if yours is clay, do amend with loads of compost. An excellent process to follow is to feed your soil first, then feed your plants. Before planting, prepare your beds well, digging them over and adding compost and bone meal. Once they’re in the ground, give them a thin layer of compost mixed with a dusting of bone meal around the base of the plant, and do the same again in spring.  

How to plant bearded iris

The most common mistake people make when planting out their bearded irises is planting them too deeply. Unlike true bulbs which are generally planted at least twice as deep as their height (excepting amaryllis / Hippeastrum) that prefer to have their head and shoulders above ground), these rhizomes should be planted just barely below the soil surface, with the tops of the rhizomes just visible and the roots spread out downwards. The tops of the rhizome become hardened during the hot summer months, which protects them from pests and diseases. If your area is very hot, or your soil is quite sandy, you can happily cover the rhizomes very lightly with a centimetre or two of soil to help keep them cool. If you want a dense, almost instant effect, plant them closer together, around about 20cm apart. This will provide the best display. You should see new growth happening within a couple of weeks of planting, but it does depend on the time you plant them, as well as where you live. This will also help predict whether they bloom in the first spring after planting – but be patient – they’ll soon reward you with a bounty of blooms. These are happy jostling amongst other plants too, especially those with fine foliage such as Lobelia or Alyssum.

Feeding and watering bearded irises

You should give your bearded irises Hadeco Bulb Food in early spring and late summer. Then water well…They need regular watering, especially in the winter rainfall regions during summer time, and especially in arid regions of the country. This being, three to four times a week and more frequently when they are flowering. Just make sure that they don’t end up standing with wet feet. The rhizomes may just rot if there’s too much water, and they can’t breathe if they’re waterlogged. So don’t overwater them – once they’re established these water-wise wonders only require watering once the top 10cm of soil dries out. 

Further care

The only problems that you may encounter with your irises is if you have long periods of wet weather, which could soften and weaken the rhizome, allowing slugs and snails to get at them, as well as setting up an environment for fungal diseases. If you regularly clear the bed or pot of leaf litter and other debris, it will help avoid conditions conducive to rotting. When numerous leaves turn brown or yellow, and start  falling over, remove some soil around the rhizome to have a closer look to find out whether rotting is happening. If there is, cut out any mushy or soft parts. At the same time, you can check whether there are any iris borer worms about. If you see any worms on the leaves, remove them from the plants before they can get down into the rhizomes.

Pruning and mulching

Cold spells are what set their clocks for flowering in spring, so you’ll find them resting during the heat of midsummer, although some re-bloomers will flush again in late summer when the temperatures have dropped. In autumn, trim away any dead foliage and prune back the leaves to about 20cm, then add mulch.


Do keep up a good weeding regime, so that the irises don’t have to compete with others for water and nutrients. Remove dead leaves and spent blooms by cutting them off at ground level on a dry, sunny day so that sunlight gets right down to the rhizomes.

If you haven’t tried planting any members of the iris ‘bulb’ family before, make this your first. You’ll soon understand why so many artists make them the stars of their paintings…

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