German Irises put on quite a display with their spectacular colors, unique flower forms, and foliage. Also known as a Bearded German Iris and Tall Bearded Iris, these plants can grow anywhere from 8 to 48 inches tall and bloom in a variety of colors, some multi-colored.
Tips for Growing German Bearded Iris
Bulbs, or rhizomes, should be planted in late summer with plenty of time for rooting before cold weather arrives. Plant bulbs even with the soil (too deep and you're likely to see rot) and in loamy, well-draining soil. A slope or raised bed is best. German Irises prefer lots of sun, but if you're in a hotter climate, try to plant where sun exposure is 4 to 6 hours, with shade the rest of the day.
Blooming will begin in early May for most areas of the US and will continue through mid-June, depending on climate. For care, water generously right after planting and infrequently once established. Fertilize German Irises with a high phosphorus fertilizer every few years.
German Iris Planting and Growing Tips
Plant in late summer or fall, in free-draining soil, in full sun or partial shade. Plant horizontal rhizomes so that the top 1⁄3- 1⁄2 is above the soil level. In hot areas, plant the rhizomes just below the surface and grow in light shade. Space 12-24" apart. Water deeply during periods of drought. After the flowers have faded, cut back the flowering stem and trim the foliage into a fan shape about 12" tall. Grows 30-36" tall. Blooms May. Hardy in zones 4-10.
Dividing Bearded Iris Rhizomes
Most bearded Iris need to be divided every 3-5 years. These are the steps to take to divide iris rhizomes:
- Prune Iris in late summer or early fall when the foliage starts to fall over (if this has not been done earlier). With a sharp knife, cut the foliage 8-10" above the soil level. Trim the plant into a fan shape.
- Carefully dig up the old clumps. Divide rhizomes with a sharp knife. To avoid spreading disease, dip the knife in rubbing alcohol or a 20% solution of household bleach between each cut. Discard the oldest (center) part of the rhizome. Check for evidence of disease or borers. Destroy (do not compost) any infested rhizomes.
- Make sure each new division has a strong root section and a single fan of leaves. Dust the cut surface with powdered sulfur and allow to dry for 1-2 days. The sulfur acts as a fungicide and helps avoid problems with disease and pests.
- Replant the horizontal rhizome with the top 1 ⁄3- 1 ⁄2 of the rhizome showing above the soil. Plant with the fan of the leaves pointing in the direction you want the plant to grow.