Dear Carol: My irises never stand upright and always fall to the ground. This is true for all the groups of them that are around my house. What can I do now, if anything, to prevent that from happening next year? -- S.L., via email.
Dear S.L.: Some tall bearded irises simply do not have stems strong enough to support the flowers. This is a characteristic of the variety, but is not a desirable trait. These irises will always have to be staked. Be careful not to put the stakes through the rhizomes, and tie each flower stem, as it develops, in several places with figure-8 ties to just below the lowest flower.
There's an old joke about the winner of the 1984 Dykes Medal, the top award of the American Iris Society. The variety is 'Victoria Falls,' and the punchline is "Yes, she does."
Many peonies have the same issue, but stems sturdy enough to support the flowers look too thick and out of proportion somehow. I use supports on most of them.
If the irises are not healthy, there's a different problem. The wet weather this spring contributed to bacterial soft rot. The rhizomes turn to smelly yellow mush and the plants collapse.
Bacterial soft rot often occurs because the rhizomes have been damaged by slugs and snails or by borers, the larvae of a moth. The plants can have rot, borers or both. The leaves will fall over, and upon investigation, they can be lifted away from the base and will look rotten or chewed up.
Rot and borers call for action. Dig the irises up and cut the foliage back to 8 to 12 inches to make the plants easier to handle. Trim away the bad spots on the rhizomes. Discard all the old, soft, hollowed-out parts and save only firm healthy rhizomes with new fans of foliage. Let the cut areas dry in the sun for a couple of days before replanting.
At the end of July, the borers are large and about to pupate. Destroy any larvae or pupae you find in the rhizomes or the nearby soil. The larva is white with a brown head and the pupa is shiny reddish brown.
Consider a different planting area. Bearded irises need sun and well drained soil. Wet soil will promote rot. If the borers have pupated, they are in the ground. The adult moths emerge in late summer and are active until frost. The females lay their eggs on the iris leaves. The moths are good fliers, but there is no reason to make life easy for them by replanting the irises in the same place.
In theory, iris borers affect all types of rhizomatous irises, but the ones with larger rhizomes seem to be more affected than those with smaller rhizomes like Siberian irises and some species.
Carol T. Bradford, of Syracuse, has been gardening in Central New York for more than 25 years. Send questions in care of Home & Garden, The Post-Standard, P.O. Box 4915, Syracuse, NY 13221, by fax to 470-2111 or by email to email@example.com. Letters might be edited for space and clarity.