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Bearded Iris
Bearded iris will grow and flower well in most gardens provided they have plenty of sun and good drainage. If you can provide it, irises prefer a fairly neutral soil but also do well in alkaline or chalky soil.
If you have bought your plants for a mixed border it would be best if the rhizomes are planted so that they are not shaded from the sun.
Irises like reasonably good drainage, especially in the top 20-25cms of soil. If you have a heavy loam or clay soil it may help to dig in some coarse grit where you intend to plant. Alternatively, why not try growing them in a raised bed?
Like most plants irises appreciate any soil preparation you can give before planting. Dig in some well rotted manure or good garden compost to provide nitrogen and other nutrients. This will improve the physical condition of the soil as well. However, don't use fresh manure immediately before planting. If your soil is acidic lightly fork in some lime and to get your plants off to a good start in any soil, include a handful of bonemeal.
Planting
Pot grown iris should be planted to the same depth as the compost level in the pot. Individual rhizomes of dwarf iris can be spaced 15-22cm (6-9ins) apart and intermediate and tall bearded irises 22-30cm (9-12ins) apart. Firm in well and water.
Bare rooted iris has been despatched freshly harvested and would benefit from being planted as soon as possible. Soak the rhizomes in water now and leave for about an hour. If you can't plant them for a few days, plunge them into a tray of moist peat or sand after soaking.
Don't worry about any old dead roots that you see. These are spent and will soon be replaced by fresh young ones.
Dig a broad and shallow hole with a trowel and plant each rhizome, spreading out its roots on either side. Fill in the hole so that the upper surface of the rhizome is at about soil level. Sometimes it may be better, particularly in a clay soil, to plant the rhizome slightly deeper than this to avoid wind loosening your iris and/or winter frosts lifting it. Don't worry too much about this as your plant will find its own level as it becomes established.
Feeding
In the spring your irises will benefit from top dressing with a compound fertiliser such as Growmore. A second top dressing of bonemeal can be applied after flowering if you wish.
Dividing
Irises should be divided every 3-4 years otherwise the clumps will become woody and produce fewer flower spikes. Splitting the clump is best done straight after flowering, or before the end of September. As you do this you will notice that the youngest and healthiest rhizomes are on the outside of the clump. These are the pieces to replant. The old pieces of rhizome can be burnt or composted.
Diseases
Irises are generally healthy plants but look out for:
Rhizome Rot This may occur in the spring. It normally starts at the bottom of the stem and then travels down into the rhizome where the base of the plant becomes brown, soft and foul smelling. The affected parts should be cut away, back to clean tissue, and a fungicidal powder dusted onto the rhizome. Rhizome rot rarely kills a plant outright if the correct action is taken immediately.
Scorch (or Fire) You can recognise this quite easily as the leaves turn bright orange/brown and look as though they have been scorched. This is probably due to lack of moisture or to starvation. Sometimes plants can be saved by replanting in fresh ground but in most cases it is better to destroy affected plants.
Leafspot This may be a problem during the spring and summer, particularly after a spell of wet weather. You will see small brown spots on the leaves. They rarely do much damage but are unsightly. Affected leaves can be cut back and burnt. Regular sprays of a systemic fungicide during the spring and summer should control it.
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