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German Bearded Iris are the royalty of the spring garden with their gorgeous, orchid-like flowers held on stems up to 40 inches tall and as short as 6 inches. Jung Seed has an amazing selection of varieties in a rainbow of color combinations – solids, bicolors and blends, many splashed, striped, picoteed and all with exquisitely laced and ruffled petals.
Hardy in Zones 3 through 9, the plants have simple needs, namely a sunny location and good soil drainage so the rhizome doesn’t rot. They can be transplanted almost anytime, but will obtain most growth if planted from late July through August so the semi-dormant rhizomes have a chance to root down and establish before winter.
If you have poorly drained soil, incorporate a good amount of sand and organic matter into the soil. Making a raised bed will also help with drainage.
Planting Iris at the right depth is also important. If planted too deep, the center of the fleshy rhizome may rot, especially if soil is wet. When planting, dig a hole large enough to spread the roots. If the roots are too long, cut them so they do not have to be bent to get them into the hole. The hole should only be deep enough so the top of the rhizome is covered with only an inch or less of soil.
Mixing a well-balanced fertilizer with the soil when planting will get them off to a good start. After planting, further fertilization isn’t needed if the iris is growing well other than giving them an annual topdressing in early spring each year. Watering is only necessary to get the iris started. Their root system is capable of storing water once established.
Here in Wisconsin and neighboring states, we often experience freezing and thawing that can cause fall planted perennials to heave out of the ground, certain death for them when their roots are exposed to the elements. Therefore, for the first year after planting we recommend applying a winter mulch as an insurance policy. The mulch should be clean hay, straw or marsh hay, applied 6 to 8 inches deep. Apply the mulch only after the ground is frozen. Once established, mulching is not necessary in future years.
Every 3 or 4 years your iris plants should be divided to maintain their vigor. The best time to divide them is 3 to 4 weeks after flowering. Divide the clump with a sharp shovel, removing half to two-thirds of the clump. The cut surface should be left exposed to the sun for about a week. Then cover the cut surface with soil. After dividing, fertilize the plant with a well-balanced fertilizer. The portion that was removed can be divided by separating central rhizomes with a couple fans on each. Cut the leaves back to half their size and replant.
Iris have few problems, but the iris borer is their worst enemy. The adult moth lays its eggs at the base of the leaf blades where they overwinter, then hatch in late spring and begin eating their way up the leaf blades. This is about the only time you can easily control this insect as they then reverse and bore into the central rhizome. Once in the rhizome, they are not easily controlled. Symptoms of their presence are the ragged edges of the leaf blades.
Dwarf Iris belong to the same family as the tall German Bearded iris, but are much shorter and can be planted in the front of the flower border, making a terrific show en masse or as a colorful accent in rock gardens.
Also consider adding Siberian iris to your flower border. They bloom about the same time as German bearded iris and have the added advantage of having attractive, long-lasting, spiky foliage that forms large clumps, very similar to the effect provided by ornamental grasses. Siberian iris do not have any insect or disease problems that plague them. Divide them every four to five years to keep them looking nice.