Dwarf Iris Bulbs are grown from bulbs - rather than the rhizomes of the large bearded irises. The Iris reticulata bulbs characteristically have a net like skin covering, are small and usually off white - pointed at the top.
This group of dwarf iris bulbs are generally known as Reticulata Irises and are all early spring - late winter - flowering - often to be seen popping through light snow. Needless to say, Iris reticulata bulbs are winter hardy in most areas.
These dwarf Irises are easy to grow and are amongst the first of the spring flowering bulbs to show though and break into flower - regardless of weather is seems.
Small Iris reticulata bulbs are normally available in late August from garden centres - often sold as pre-packs. The bulbs are small, and firm bulbs should be selected, but please don't go squeezing them. Being pointed at the top, there should be no problem in which end goes up when planting.
Iris reticulata 'Joyce'
If bulbs have been purchased, then they should be planted immediately after purchase - if weather conditions permit. Pots of Iris will often have been grown under cover of glass or polythene to get them into perfect flowering condition, so flowers could possibly be a little tender if planted out right away in flowering positions. Better to allow the flowers to die down, then gently part the bulbs and plant in flowering positions.
Bulbs should be planted with the tops just below soil level - even if the potted specimens have the bulbs showing above to pot soil.
These Irises prefer full light and are not generally suited to growing in shade - though light dappled shade seems ok. They draw their strength from the foliage after the flowering has ceased, and any shade at that time - such as with braking foliage in woodlands, would hinder that process and thereby weaken the bulb considerable.
Light soil is preferred - especially only slightly moist during the long dormancy period of summer. Not waterlogged.
Once established after a few years, there should be regular flowering. However, the first two years after planting might see some erratic flowering of this type of Iris.
The same is true if you decide to divide the bulbs and re-plant. Far better left alone.
From experience, Iris reticulata bulbs seed propagation is not easy. But, seed can be gathered and sown in gentle heat - no more than 50deg, or better still to place in coldframe and let the gentle warmth of spring do the job.
Division is possible with larger clumps, but preferably to divide into smaller clusters of several bulbs rather than try to separate every bulb. This should be done in in spring - after flowers have died down, but whilst foliage is still evident.