The rhizomes of my bearded iris are pitted with small holes, and last summer I got only three blooms from the whole bed. Should I throw them away – and can I plant fresh ones in the same spot?
The holes could be wireworm, but usually the rhizome goes mushy and rots quickly. You can easily check: leave a potato by the rhizome for a couple of days. To a wireworm, a potato is far tastier than an iris, so if they are present, you’ll find them munching the spud. If the holes are dimpled and black, and the rhizome is firm, the holes may be marks left from old roots that have died back.
Bearded iris rhizomes need to bake for at least two-thirds of the day, preferably with afternoon sun, if they are to flower well. Any competition (weeds, congestion, shading from a tree) will make them sulk. Dividing is usually done in late summer, but you could try the Doddington method in June; search YouTube for a how-to.
Feeding is another reason bearded irises give up growing. They need something well-rounded with high potassium to promote flowering, such as bonemeal or an organic feed such as Chase slow release, applied in spring and autumn.
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