Fall Care for Healthy, German Bearded Iris

Article written by Saturday6TM blogger Matt Mattus from Growing with Plants

Of all of the iris species, the large German Bearded Iris is by far the most striking. German Bearded Iris can be identified by their thick, ginger-like rhizomes, which sit on the surface of the soil, and by their large, flat fan-like leaves. They are common, old-fashioned perennials often seen in cottage gardens or perhaps even in your grandmother's garden, but their culture can be confusing for many new gardeners.


The bearded iris group contains many divisions - ranging from very dwarf and miniature types to mid-sized (knee-height forms) all the way to the large, 3-or 4-four foot tall varieties - and they come in most every color of the rainbow. Many are fragrant, particularly the heirloom varieties with scents reminiscent of concord grapes, grape soda or even root beer. German Bearded Iris can also be identified by their 'beards,' which appear on the large, down-facing lower petals (called 'falls'). The beards are often bright yellow, white or violet-blue on a contrasting petal.

Bearded Iris with large rhizomes need two essential tasks completed if one wants to keep the display looking at its best. First, clumps should be divided every three years in late June or early July just after they finish blooming.

The second task, perhaps the most important come autumn, is a task many gardeners forget to perform. The common Iris Borer (a Lepidoptera larva) starts its life cycle in September, when the adult moths lay their eggs on dead or aging (yellowing) iris foliage. The iris borer causes most of its damage in the spring, when the eggs hatch and the larvae feed and crawl around the rhizomes, leaves and floral stems silently eating. Damage is usually identified after it is too late - when buds drop, rhizomes rot or foliage wilts with the tell-tale swirling trails of insect damage.

To avoid damage, the trick is simple - sanitation. By simply removing all aging or dead foliage in the autumn - and with it, the moth eggs - one can avoid a severe infestation. One female Iris Borer moth can lay nearly 1,000 eggs before frost, so be studious in removing old foliage. Be sure to destroy all foliage, and not compost it. Also, make sure to keep the rhizomes clean and free from mulch or other decaying foliage.


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