Learn about identifying, growing and harvesting irises
You will gain an in-depth appreciation of the iris, how to grow them to achieve optimum results and the identification of different varieties of irises. Significant sections are included on landscaping with irises, hybridisation and propagation, harvest, post-harvest treatments, achieving and assessing quality, and exhibiting the flowers.
There are 8 lessons as follows:
- Review of the system of plant identification
- Information sources
- Pruning, etc.
- Propagation and Hybridisation
- Review of Major Types of Irises
- Pest and Diseases
- Irrigation and Hydroponics
- Landscaping with Irises
- Harvest, Post Harvest, Exhibiting and Quality
Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.
Duration: 100 hours
What Do You Know about Irises?
There are thousands of different types of iris that are cultivated around the world.
These plants vary in appearance, generally having grey-green to deep glossy green sword-shaped leaves usually arranged like a fan. The flowers usually have three outer petals called 'falls' and three inner petals called 'standards'. Bearded irises have hairs on the falls. Given the complexity of this genera, Irises have been categorised in different ways. Botanists tend to classify them into various genera, subgenera, and sections. Gardeners often place them in two groups of bulbs and rhizomes. These groups may be divided further so the bulbs include Dutch and English Irises (Xiphium), Junos Irises (Juno), and Reticulata irises (Iridodictyum), and the rhizomes include Bearded Irises (Iris), Beardless Irises (Limniris and Xyridion), and Crested Irises (Crossiris).
Most grow best in fertile, well-drained soil in full sun. The optimal soil pH is 4.5 7.5 and the ideal pH is around 6. Most do not tolerate lime. In hot climates they should be planted deeper. In wet situations plant them shallower or on mounds. Irises are generally heavier feeders than other bulbs and rhizomes.
The bearded iris seems to be more susceptible to diseases than some of the other groups. Generally, rhizomatous species are prone to rust appearing as reddish brown lesions, leaf spot (usually caused by damp conditions), cucumber mosaic virus and arabis mosaic virus which cause chlorosis of the leaves and distorted growth, and rhizome rot which reduces rhizomes to slime. The bulbous irises are prone to iris mosaic virus which causes chlorosis and distorted or stunted growth, ink disease which results in black spots and lesions, grey bulb rot which is a fungus that hinders growth from the tip of the bulb, blue mould which is a fungus that destroys stored bulbs, leaf spot which causes foliage to decay, and iris scorch which causes leaves to redden and decay. Pests include narcissus fly larvae which attack the above ground parts of bulbs, aphids which are more of a problem with bulbs in storage, eelworms, slugs and snails which attack both bulbs and rhizomes, and some caterpillars which are partial to bearded irises.
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