To propagate Japanese iris, the most common method is by division, where you dig up the established clump and separate it into individual plants with a sharp knife, replanting each section in a new location; the best time to do this is either in early spring or fall, ensuring each division has healthy rhizomes with at least one fan of leaves.
Key steps for propagating Japanese iris by division:
Dig up the clump: Use a spade or pitchfork to carefully dig up the entire iris clump from the ground.
Wash off soil: Rinse the soil off the roots with a hose or soak the clump in a bucket of water overnight.
Divide the rhizome: Using a sharp knife, cut the rhizome into sections, making sure each section has at least one healthy fan of leaves.
Remove old roots: Trim away any old, dark roots, focusing on the newer, white roots.
Re-pot the divisions: Plant the divided sections in new locations at the same depth as the original plant, ensuring the top of the rhizome is slightly exposed above the soil.
Water thoroughly: Water the newly planted irises well to settle the soil.
Important points to remember:
Division frequency: Japanese irises should be divided every 3-4 years to maintain healthy growth and prevent overcrowding.
Soil preparation: Before replanting, ensure the soil is well-drained and amended with compost.