The Iris Genus
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Overview:
Iris basically fall into four categories, each with their own sub-sections.
The categoreis are; Bearded, Beardless, Bulbous,and Crested.
Bearded section:
Pogoniris
The flowers in this category have hairy beards on their falls, the roots are rhizomatous, and the leaves are flat.
They flower from May to June, and grow to a height of approx 600mm (24")
They will grow in most types of soil, and flower best in full sun.
Do not plant deeply to allow the rhizomes to develop at or near the soil surface.
Plant 100mm (4") apart and approximately 50-75mm (2"-3") deep.
Sub-sections:
Arillate group:
The rhizomes are stoloniferous and generally grow 25-75mm (1"-3") under the surface of the soil.
Eupogon group:
The rhizomes grow on the surface of the soil.
Beardless section:
Apogon:
The flowers are beardless, the falls are smooth, the roots are rhizomatous, and they have flat slender leaves.
They flower from May to June, and grow to a height of approx 600mm (24")
Sub-sections:
Californicae-Pacific group:
The foliage is usually evergreen, the rhizomes are generally long and slender with a sparse root system.
Laevigateae group;
The foliage is deciduous and the rhizomes are slender.
This group can be planted in wet conditions such as shallow water or boggy soil as well as ordinary soil.
Sibiricae group:
The foliage is deciduous and the rhizomes are quite short with numerous roots and should be planted 25-50mm (1"-2") under the surface of the soil.
Hexagona group:
The foliage is usually evergreen, and the rhizomes are generally long and slender, with a creeping root system.
The flower stems tend to zig zag.
Spuria group:
The foliage is evergreen and the rhizomes are fibrous and grown 25-75mm (1"-3") under the surface of the soil.
Bulbous section:
Reticulata group:
The bulbs are small and are covered with a netted husk, the leaves are tubular and multi sided.
Xiphium group:
The bulbs are medium sized and covered with a smooth husk, the leaves have a channelled cross-section and are generally few in number.
Juno group:
The bulbs are small with fat storage roots attached to the base, and the leaves have a channelled cross section. The flowers are produced in the leaf axils.
Crested section:
The flowers have fleshy crests on the falls instead of beards, and the rhizomes are slender and grow on or just below soil level.
The leaves are flat, broad and glossy.
Location:
Iris varieties need the right growing environment for example; arid desert conditions in full sun, damp conditions in shade, permanent immersion in water.
Placing them in a wrong location could kill them off.
Pests and Diseases:
Aphids:
Bearded varieties being overwintered in a cold greenhouse can be the subject of attack by grey aphids,these can be killed off by spraying with a suitable systemic insecticide.
Alternatively run your index finger and thumb up the fan squeezing at the same time,this is a quite effective control, albeit slightly messy.
Greenfly; can attack in the garden during hot but damp weather, and the same solution can be applied.
Slugs and Snails:
These can decimate newly planted iris and seedlings overnight so preventative measures should be taken to avoid this.
Measures such as removing them by hand, scattering slug pellets, spraying with a slug/snail repellant, beer traps, or using nematodes can all help.
Providing a slug / snail shelter can help manual control.
This is done by placing a slightly raised plank of wood (or similar) in a convenient spot to allow the slugs/snails a place to crawl into during the day.
Then it is simply a case of lifting the plank daily and removing any that have taken refuge underit.
Rust:
This disease manifests itself as brown spots on the leaves, usually appearing after bloom, but can happen at any time.
It is normally not harmful to the plant/s.
Allow the leaves to die down then collect and burn them to prevent spreading the disease.
A fungicidal spray may control the rust, but will not remove the spots.
Root Rot:
The symptoms of root rot is the softening of the rhizomes and a change in their colour to buff-yellow colour.
When the rhizome is squeezed it will yield to pressure, and if it punctures, it will give off a noxious smell.
Cut back the affected section to unaffected tissue,dust the cut ends with sulphur powder, then burn or remove the affected part off site to prevent spreading the disease.
Do not place it in the compost heap!
If possible, remove the soil from the original position, and replace with new before planting anew.
Another symptom is when a healthy looking fan keels over, then on examination the base of the leaves has turned translucent.
Scorch:
This is a condition where the leaf starts dying back from the tip, first turning orange/red then brown.
There is currently no known remedy for scorch, so all affected plants should be lifted and burnt to prevent spreading the disease.