Planting tips for Iris
As soon as your parcel are delivered, unpack and check the plants. If there are any problems let us know immediately. Remember however that the size of rhizomes can vary appreciably according to the variety and that we send out only vigorous and perfectly healthy plants.
Plant your irises as soon as possible. If they can’t be planted immediately, store them in a cool dry place, but for no more than 30 days.
What aspect ?
Full sun or at least a good half day of sun.
What soil ?
A light well drained soil, iris suffer in wet conditions. If your soil is too wet, plant the rhizomes on a mound to improve drainage. Break up the soil to a depth of 25cm to 30cm. If your soil is heavy dig in sand to improve drainage. Soil can be alkaine (limey), neutral or slightly acid. If its too acid incorporate magnesium limestone (50g/m²)
What planting distance ?
Leave at least 25cm between every rhizome. Planting closer will give a better immediate effect but the plants will soon need to be thinned.
What planting period ?
Mid-July to the end of August. This is the best time because the rhizomes are vigourous and will have time to become well established before winter. However, you can continue planting until the end of September. Your iris will flower from the following spring onwards.
How to plant ?
Dig a hole and create small mound of fine earth at the bottom. Place the rhizome on this mound. Spread the roots carefully around the mound and then fill in and firm gently. The rhizome should be barely covered and with 25cm between each rhizome. Avoid planting iris doo deeply. Water thoroughly after planting.
What fertilizer ?
In good soil iris need no additional fertilizer, in poor soil incorporate bonemeal, blood and bone, or hoof and horn, or compost. Avoid using a fertilizer too high in nitrogen which encourages leaf growth at the expense of flowering and can cause the rhizomes to rot. On poor soil you can use an organic fertilizer (3.5.7 type) in the spring.
General care and propagation
Iris need relatively little care. Keep them weeded and remove the faded flowers and unslightly leaves. In the autumn remove the yellow and dead leaves but don’t cut back the green leaves.
About once every four years its necessary to thin the clumps. This avoids the rhizomes becoming choked which may reduce flowering. You only need to remove the oldest rhizomes from the centre, keeping the most vigourous. This best time to do this is at the end of the summer. The rhizomes that you want to keep can be planted in a circle, with the leaves of the rhizome towards the outside. 3 – 5 rhizomes are needed to make a good clump. Leave 25cm to 30cm between rhizomes and 1 metre between clumps. Hand weeding is always best to avoid damaging the rhizomes, try to keep the soil clean particularly from couch grass and bindweed the sworn enemies of iris.
The main and the most serious disease which affects irises is rhizome rot (bacterial rot), which appears during the flowering time. The simplest way to treat this is to uncover any affected areas and let them bake in the sun. If this isn’t sufficient, dig up the iris and cut off any diseased parts. Disinfect the wounds with a 10% solution of bleach (1 part bleach to 9 parts water) and leave the rhizome to dry for two days in the open before replanting. Any plants that are too badly affected should be burnt. Marked leaves are not a problem for the plant but if you prefer you can treat with a fungicide (Bordeaux mixture) in the spring. The best form of prevention is always to keep the plants weed free and grown in appropriate conditions.
In spring insect larvae can attack iris, eating leaves and then rhizomes. Other enemies include slugs and snails. To reduce these problems to a minimum always keep the beds clean.
How to use iris ?
This depends on the type of iris, its height and vigour.
They make very good cut flowers and look wonderful in a large vase. Take care to remove faded flowers to encourage all buds to open.