Growing Bearded Iris

The bearded iris, Iris germanica, has fuzz or a ‚”beard” on the lower petals of the flower. These three outer petals are called the falls. The three inner upright petals are the standard. Another distinctive characteristic of the bearded iris is the sword like leaves.

This iris grows best in full sun with amended soil, and a fall clean up are essentials for success. This iris requires fertilization at transplanting time and as a yearly treatment in the spring. A low nitrogen fertilizer combination such as 10-20-20 or 5-10-10 is recommended.

Fall Cleanup for Bearded Iris

Bearded iris require fall cleanup, primarily because they are susceptible to iris borer. The clearing out of dead leaves and debris from around the plants is essential, eliminating a place for eggs of iris borer to over-winter. As all the flowers fade on a stalk, removing them throughout the growing season will help keep the garden clean, too. All plant debris from the clean up should not be added to compost piles.

Insect Issue Iris Borer

Iris borer is the plant’s major insect issue. To minimize the iris borer’s impact, understanding its life cycle is helpful. The iris borer’s eggs are laid in old leaf debris that surrounds the plant, during the fall. After the eggs hatch in spring, the caterpillars drill into the leaves, and feed on the rhizome. The iris borer pupates in the soil, develops into a moth and the cycle starts over the following fall.

The feeding on the rhizome by the caterpillars may also allow bacterial soft rot to be introduced. Again, fall clean up is an essential garden routine for healthy plants. Well thought out plant spacing and transplanting is a good practice, too.

How to Transplant Bearded Iris

Bearded iris should be dug and divided every 1-3 years, after flowering. The midsummer to early fall are excellent times for this project. When dividing there should be, at least, one set of leaves, called a fan, on the rhizome. Face the fans outward and space them approximately 2 feet apart. The rhizome should sit high in the soil. These guidelines help improve air circulation for healthy plants.

Wood chip mulches for planting beds containing bearded iris are not recommended. In a colder region with unreliable snow cover, use a temporary protection of evergreen boughs but remove them in early spring.

The reblooming bearded irises will repeat color, some in to October. But for healthy bearded iris all require high maintenance attention. Beardless iris continues to be a better choice for gardeners with less time.