How to grow bulb irises

Choosing bulb irises

All you need to decide is when you need colour in your garden – to start the year, or to accompany summer-flowering plants.

Iris × hollandica types reach 60cm (2ft) in tall when in flower and have unobtrusive grassy leaves. Colours range from yellow, blues, purples, whites and bi-coloured flowers.

Iris reticulata is diminutive in stature at 15cm (6in) and flowers in February to March to start the year. The leaves die away in summer when the bulbs are dormant.

Where to plant bulb irises

When and how to buy bulb irises

You can buy iris bulbs in September and October by mail order, in nurseries, garden centres and DIY stores.

Sometimes you will see potted Iris reticulata types for sale in garden centres when they are flowering in spring; this is more expensive but you get instant enjoyment.

Planting

Choose a sunny position where the soil is well-drained. Iris reticulata planted en mass under a tree canopy can create an impressive spectacle to herald spring.

Plant bulbs as soon as possible after purchase. Planting them up to 15cm (6in) deep can help encourage your bulbs to reflower more reliably the following year. Space about a minimum of 5-7.5cm (2-3in) apart.

Plant potted bulbs just as you would for other perennials, with the compost on the top at the pot finishing just below the soil surface.

Routine care

Happily, these irises are very low maintenance. However, it’s best not to consider Iris reticulata as long term plants, especially on a soil that isn’t perfectly well-drained. Dutch iris are more reliable especially on a well-drained soil. Replacement is cheap and bulbs are widely available.

No actual pruning or deadheading is required. The foliage will die away naturally after flowering so just pull away the foliage once dead and straw-brown. At this stage, you may want to mark where the bulbs are (such as with a cane or label) to prevent you digging them up by mistake.

You can divide the bulbs of Dutch iris and Iris reticulata types in autumn. Each single bulb tend to split into many ‘daughter bulbs’. Pot these small bulbs into 7.5cm (3in) pots with a mix of John Innes No. 2 compost and 10% horticultural grit by volume.

Water the compost to keep moist from autumn to late spring to support good development. They can take a couple of years to reach flowering size.

Although iris are usually trouble-free, slugs and snails sometimes favour bulb irises