The cultivation required by the different types of iris run the whole gamut from arid desert conditions in full sun, through damp conditions in shade to permanent immersion in water. The wrong conditions will kill off the plants, so care should be taken to supply as correct a growing position as possible before buying the iris, and especially before planting it.
Having said that, most iris can tolerate a certain amount of variation in their growth habits, witness the survival of bearded iris through the rains to which they have been subjected in the five months from October 2000 to February 2001.
The BIS provides new members with instruction booklets on how to grow iris in your garden, which will start them off on the correct road to getting it right.
Pests and Diseases
In the main, iris are not prone to major pests and diseases in the UK. Newly imported bearded varieties being overwintered in a cold greenhouse can be the subject of attack by grey aphids, but these can be killed by spraying with a suitable systemic insecticide. However, if you prefer a "green" solution, running a finger and thumb up the fan squeezing at the same time, is effective, albeit slightly messy.
Green aphids can attack in the garden during hot but damp weather, and the same solution can be applied as above. The worst pests are slugs and snails, which can decimate newly planted iris and seedlings overnight. Preventative measures range from a scattering of slug pellets (or better still the lesser-known liquid alternative), to 'green' remedies of nematode control, beer traps, or even the simple, but time-consuming process of collecting them by hand in the mornings and evenings. The job needs to be done using whichever method you prefer, as you really do not want any iris, much less your new $50 import opening up with damaged blooms.
There are three main diseases to look out for: rot, scorch and rust. The latter manifests itself as brown spots on the leaves, usually appearing after bloom, but can happen at any time. While it is disfiguring to the plant, it has not yet been proved to be harmful, and in the fullness of time the leaves will die down when they should be collected and burnt to prevent spreading the disease. A fungicidal spray will control the rust, although it will not remove existing spots.
Scorch is a condition where the leaf starts dying back from the tip, first turning orange/red then brown. It usually only affects one plant in a block, leaving all its neighbours untouched. There is currently no known remedy for scorch, so all affected plants should be lifted and burnt to prevent spreading the disease.
Rot attacks the rhizome turning it buff/yellow in colour and becoming soft. Quite frequently the first sign of rot is when a healthy looking fan keels over, and examination shows that the cells at the base have turned translucent. The rhizome will yield to pressure, and if the skin is punctured, a noxious smell is released. Lift the affected piece, and cut back to white flesh, discarding and burning the bad part to prevent spreading the disease. Dust the cut end with sulphur powder, and replant 24 hours later in a different place. If possible, remove the soil from the original position, and replace with new before planting anew.
Modern hybrids of any type are virtually unobtainable from garden centres, and anyone wanting to source a particular species or hybrid will need to apply to a specialist nursery. Most of these nurseries do not carry the whole range of even one type, much less of all types, so be prepared to have to search round a little. The RHS Plant Finder lists some the species and hybrids currently available, but you might draw a blank even there. The best way to look for that elusive variety, is though the catalogue library of the BIS which is available to all members, or by joining one of the specialist and/or local groups, and attending their plants sales.