Bearded Irises are the sun lovers of the Iris family and are so called because of the "fuzzy" little growth that appears just at the top of the falls. The falls are the 3 bottom petals of the flower; the 3 top ones are called standards. All Bearded Iris flowers are made up of these 6 petals. If the flowers are a single colour this is often described as a "Self". Multi-coloured or bi-toned flowers have all sorts of fancy names such as "Amoena" which means white standards and coloured falls or "Plicata" which means that the flowers have dots or lines on the petal edges. Bearded Irises come in all sizes from the very small - Miniature Dwarf Bearded - to the very tall - Tall Bearded - with an in-between group known as Intermediate and Border Bearded. Bearded Irises grow from a rhizome which is actually a swollen stem and this is why they are known botanically as rhizomatous. Irises are named after the Greek Goddess of the Rainbow and with their attractive grey foliage and stunning flowers they are one of the easiest and most rewarding of perennials to grow, here's how.
Situation - Bearded Irises require full sun for at least half a day in summer, insufficient summer sun will hinder the development of the flowers. If at all possible full sun all day is desirable for most. As much as Bearded Irises like to bake in the summer heat, they also like to be nice and chilled in winter. The degree of chilling required depends on the cultivar but many Irises will require actual frosts to bloom. Some areas north of Auckland will not receive enough winter chill for Bearded Irises to bloom well.
Soil - Bearded Irises grow best in well drained, neutral to alkaline soil. In other words they will do well under average conditions.
Water - The general rule with water and Bearded Irises is that less is more. Bearded Irises are relatively drought tolerant once established and many will survive without summer watering; they certainly should not be watered any more than every 2 weeks or so in dry periods. Container grown Irises should be watered every 2-3 days in hot dry periods and new plants will need to be watered once or twice a week until they get established.
Feeding - Most Irisarians use a well balanced fertilizer such as Rose Fertilizer to feed their Irises. This is usually done before flowering around about August. A light feed can also be done after flowering as the plant will have exhausted its reserves putting on its magnificent floral display. Lime is usually applied in winter around May-June to make soil less acidic.
Cultivation - Bearded Irises should be planted with the rhizome exposed or with no more than 1-2cm of soil over the rhizome, maximum. The reason for this is to expose the rhizome to the summer heat and winter chill as mentioned above. If your garden is very hot and you are growing your Irises in an all day sun that is when it is OK to cover the rhizome with a little soil.
Your Iris clumps will establish quite quickly and will need dividing every 2-5 years. This should be done in summer, after flowering; divisions should be planted in fresh or new soil.
Never cover the rhizomes with moisture holding mulch such has pea straw or lawn clippings as this will cause the rhizomes to rot. If rot starts to happen, remove the rotten part of the rhizome with a sharp clean knife and expose the cut surface to the sun for a few days to dry out.
Pruning - Remove spent flower stalks at the base. Clean away any untidy foliage as and when it is annoying. There is no need to cut the leaves back after flowering, they will die down naturally and pull off easily with a gentle tug.
Wairere Nursery 826 Gordonton Road, R D 1, Hamilton Ph: (07) 824 3430 Email: Open 7 days 8:30am-5pm