IRISES add a touch of elegance to the flower garden. They are easy to grow and come in forms that live happily in water, in the moist boggy area round ponds in borders or in a rockery situation.

By carefully choosing the varieties you can have colour all year round.

The iris family covers more than 300 varieties, most of them ideally suited to our gardens. Their flowers range from pure white, through all shades of yellow to the deepest purples.

Some of them have the added bonus of being perfumed and by far the majority make excellent cut flowers.

A standard iris plant is recognised by its erect, sword-shaped leaves. The flowers are made up of three upright inner petals surrounded by three larger ones falling downwards.

To simplify, garden irises can be divided into three main groups, each having a different place in the garden.

Bulbous irises, which include those commonly grown in borders, dwarf winter varieties, alpine species which flower in the spring and those sold in florists shops as cut flowers.

Water irises which as the name implies grow in moist soil or shallow water, making them an ideal plant for ponds and pools.

Bearded irises, which get their name from the fleshy hairs on the falls (the downward petals) are generally grown as herbaceous border plants and include "flag" irises.

The most popular hybrids available from garden centres, or bulb catalogues are known as English, Dutch or Spanish irises. The English irises derive from Iris latifolia, the Spanish from Iris xiphium, the Dutch are hybrids. They all share a similar range of colour.

They all have different soil requirements. Iris reticulata does best in light, well-drained, limey soil. English irises prefer soil that is light and moist. Both Dutch and Spanish irises like to be planted in light, fertile soil.

Water irises need shallow water or marshy soil. Bearded irises require a fertile situation in soil that is neutral or slightly alkaline.

The one thing that they all have in common is a preference for full sun.

Once they are settled in a sunny position, they suffer from very few problems. For a succession of flowers through the summer months plant them during the autumn. In the early summer the Dutch are the first to flower, followed a few weeks later by the Spanish and then the English varieties take over.

In some areas, the Dutch and Spanish varieties may not be fully hardy and will need to be protected with some sort of cover. English irises need no winter protection.

Dwarf irises, which flower in early spring are ideal for alpine beds or rockeries as they prefer a well drained soil. They also do well in window boxes and patio pots, making a welcome splash of colour during the cold grey days of late winter.

Iris reticulata, which only grows to approximately 15cm produces delicately perfumed blue or purple flowers. Iris danfordiae is even smaller, 5 to10cm and has strongly scented yellow flowers.

Bearded irises also grow from rhizomes and this group covers most of the popular garden hybrids. They make really good plants for the herbaceous border, but they do need plenty of sun.

Their size ranges from dwarf varieties growing no more than 10cm to the tall forms which can reach heights of up to 1.5m.

Once settled, all irises are easy to look after as they need no special attention. The taller varieties may need staking. Once they have outgrown their allotted space, or they are not producing good flowers, simply divide them to create new plants.

Water irises grow from rhizomes and, as their name suggests, are best suited to waterside planting. Iris kaempferi prefers moist soil on the edge of the pool while Iris laevigata likes its rhizomes to be planted under 15cm of water.

Both of these varieties flower in early to midsummer. Water irises are completely hardy, needing no special care. Once they start to outgrow the pond the rhizomes should be divided and replanted.

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