Position - Irises prefer full sun, but good blooming can be obtained with half day sun.
Climate - Some winter cold is needed for a good blooming season. Occasional frosty areas are preferred. High summer rainfall can cause the plant to rot.
Soil - Irises are very tolerant. PH 5.5 to 7.5 they are not too fussy. They will grow in a variety of soils, but soft well draining soil is best.
Planting - It is best to plant between December and February. Irises should be dug and replanted every 3 to 4 years. When planting, the rhisomes should be level with the surface of the soil. The top of the rhisome should be visible to catch the sun and promote good blooming. Plant approx 40 cm apart.
Fertilizers - Irises will respond well to nitrogen fertilizers to promote green healthy foliage. To promote flowers add phospherous based fertilizers such as sulphate of potash or phostrogen. Irises also love lime and this helps them produce lovely blue green leaves. I prefer to use a well balanced slow release Osmocote.
Watering - A good soak once a week in Summer and Autumn and twice a week in the main growing seasons of Spring and Winter is required. Over watering can weaken the rhisomes making them prone to rot and
Diseases - Leaf Spot or Rust Virus is the most common disease of irises. It is a fungal disease that lives in soils and occurs when the spores are splashed onto the leaves when watering. Remove diseased
leaves and spray with a fungicide. I use Mancozeb. Animal manures increase the chances of Leaf Spot. Add lime to your soil to make your irises stronger.
Rhizome Rot occurs when the rhisome is too wet. Cut away infected part of the plant and dust the rest with lime. Then allow to dry out before replanting.