German Bearded Iris Rhizomes

German Bearded Iris Planting & Growing Tips

Bearded iris bulbs, or rhizomes, should be planted in late summer or fall with plenty of time for rooting before cold weather arrives, though they can also be planted in the spring. Plant horizontal rhizomes so that the top 1⁄3- 1⁄2 is above the soil level (too deep and you're likely to see rot) and in loamy, well-draining soil. Be sure to space bearded iris bulbs 12-24" apart. A slope or raised bed is best. German iris prefers 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.

Your German bearded iris flower will begin blooming in early May for most areas of the US and will continue through mid-June, depending on the climate. For care, water generously right after planting and infrequently once established. Fertilize bearded irises with a high phosphorus fertilizer every few years. After the flowers have faded, cut back the flowering stem and trim the foliage into a fan shape about 12" tall. German iris flowers grows 30-36" tall and are hardy in zones 4-10.

Read our Iris care guide to learn how to plant and grow Iris bulbs.

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:

1. Prune German irises 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.
2. 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.
3. 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.
4. 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.