Growing advice for Iris
Irises are hardy and easy to grow with shapely foliage and spectacular flowers. There is an Iris for every garden as they come in a spectrum of all the colours of the rainbow and are available in both tall and low varieties.
Iris is a genus of 260-300 species of flowering plants with showy flowers. The word ‘Iris’ is Greek for ‘rainbow’ and they certainly live up to the name by offering a rainbow of colours. Pure white, pastel colours, red, orange, yellow, blue and even black! Our own Carl von Linne was the first to describe the flower, already in his book from 1753 it is mentioned.
Irises are hardy and easy to grow, with strong foliage and spectacular flowers. To thrive, they need sun at least half the day and they thrive in most climates. Irises should be planted so that the tops of the rhizomes stick up and the roots spread out and face downwards into the soil. Note that Bearded Iris may not flower in the first year after planting.
Breeders have developed reblooming irises, which tend to flower again from late summer to autumn depending on climate and growing conditions.
Classifications of irises
Three common groups of irises to grow in the garden are: Iris Sibirica – Beach Iris, Iris Germanica – Garden Iris, Bearded Iris and Iris Pumila – Dwarf Iris. There are also hybrids (crosses).
The year of the iris
Plant irises in a sunny spot in late summer The plants need well-drained soil and at least six hours of sunlight per day. Full sun is even better to keep the rhizomes dry. Plant them about 40cm apart (less space for dwarf irises and more for tall varieties).
Fertilise with nitrogen-rich manure twice a year: in early spring and just after flowering when the rhizomes are forming next year’s flowers. Water only if it is very dry or after moving and dividing.
If you don’t want to sow your own irises, remove the seed pods that form after flowering as these take energy from the plant.
In early autumn, the leaves can be cut back to about 15 cm above the ground. This reduces the risk of pests and diseases overwintering. Make dividing a habit. Divide root clumps of iris plants every three to four years in late summer.
Growing irises
The best time to plant Bearded iris is July to September. This gives enough time for the flowers to establish themselves before winter. Dig a shallow hole large enough for the rhizome clump. Create a small mound of soil in the centre of the hole. Make sure the mound is high enough to allow the top of the rhizome to protrude slightly above ground level. Spread the roots around the mound, filling it with soil and water. We recommend planting at least three rhizomes about 20 cm apart. Direct the direction of growth away from the centre of the group. Water sparingly.
Irises prefer bright, sunny locations but can cope with partial shade. If you have heavy clay soil, improve it with some coarse sand and humus. Irises like nitrogen-rich fertilisers such as chicken manure and cow manure.
Over time, the root balls often become crowded and flowering declines. It is easy to divide irises and thus stimulate new growth and flowering. In late summer, carefully dig up the entire clump. Break or cut apart, the new younger root stems from the original centre stem, then replant. If you don’t see new buds coming from the centre of the rhizome, throw it away most likely it is too old and unlikely to flower a second time – the ‘babies’ are what you want to save.