Iris Growing Advice

Tall, bearded irises like a well-drained soil in full sun all day.  The ground should be clean and deeply dug with well-rotted manure incorporated into the lower spit.  Spent mushroom compost or good garden compost are fine, not peat (pH 7 to 7.5 is best).  Most of the iris family are deep-rooted and should be planted about 15" to 18" apart (38 to 45cm) with the rhizomes of bearded irises  lying at the surface and, in the case of bare-rooted plants, with the roots spread out and sloping down into the soil.  The leaves should be trimmed to six to eight inches (15 to 20 cm) and the roots well firmed into the soil.  This prevents wind rock while the roots are developing.  They should be watered in and not allowed to dry out for the first few weeks, allowing the roots to get started.  After that they will only need watering in prolonged dry spells and once or twice after flowering.  Leave them exposed to winter frosts and don’t cut the leaves down.  You may be reducing the production of next year’s flowers.  Simply keep them clean and tidy by removing old and brown leaves and tip the leaves that may collect leaf spot, etc.  Cut flower stalks down to 4”/10cm after flowering.  Do not cover the rhizomes or they will rot.  They should be planted within two weeks of arrival, preferably as soon as possible.


If you have purchased pots, simply fork over the ground and dig a hole in your prepared bed and place some garden compost in the bottom.  Knock the plant out of the pot and place it in the hole with the rhizome level with the soil surface.  Water it in.  If you have bought a plant in flower it should be staked until you wish to cut off the flower stalk  -  at about 4ins/10cm.  Some varieties do not rush into growth after flowering and may remain dormant for some time, even a year or so.  As long as the rhizome is firm and hard it will wake up eventually and start into growth again in the spring, but it is unlikely to flower again for another year.   After flowering, if you wish, they may be fertilised with any garden product – rose or tomato fertiliser or blood, fish and bone .


You may find that some plants are smaller than expected.  This can occur for two reasons. Firstly, the season may be late and so the plants have not grown so fast or, secondly, the variety may have small rhizomes anyway.  In either case, do not worry.  The plants will soon catch up and those with smaller rhizomes will still flower as well as the bigger ones.  New roots will rapidly appear.  Remember to water them in and, if there is a dry spell, again after a week or so.


In the unlikely event that one of our plants fails within two weeks of purchase we will gladly replace it.  After that time the problem will be in your garden. We can give no guarantee that a plant will flower in any particular season.   We usually find that failing plants are due to:


                a)     Planting the rhizome below ground level

                b)     Planting in shade

                c)     Planting in wet ground

                d)     Cutting off the leaves or covering in winter

                e)     Keeping under glass in the winter - they should be in the open.



Generally, our climate provides too much rain, rather than too little, hence the need for a well-drained soil to reduce the chance of rotting.  Irises come from a harsh environment and do not need top dressing.  By adding coarse grit to the soil the drainage is improved and the ground can be regularly tilled to keep down weeds, the main enemy of irises.  The weeds use the nutrients, keep the essential sun and wind from the rhizomes and induce disease by reducing air circulation.  The same applies to other border plants growing too close to the irises. Give irises plenty of elbow room.


After a few years they will become crowded and flower less prolifically.  They should be lifted any time after flowering and before the first frosts of autumn.  The rhizome should be broken or cut into sections of new growth ready for replanting, discarding the old parent rhizome.


Please Note:      The heights and seasons in our plant list refer to those that we find occur here in South Lincolnshire.  You may find variations according to your soil, care and climate.  Reblooming is not guaranteed.

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