Propagating Persicaria kawagoeanum from Cuttings

How to propagate the fast, fine-leaved Persicaria kawagoeanum by cuttings, with light and CO2 tips to keep its bright pink-red submersed color.

Overview

Persicaria kawagoeanum (also sold as Polygonum kawagoeanum) is a Japanese member of the knotweed family Polygonaceae, the genus that was segregated from Polygonum and carries alternately arranged leaves on usually erect, self-supporting stems. It is a fine, narrow-leaved stem plant valued for fast growth and warm light-green to orange-red color.

Underwater it converts to its submersed form quickly, within days, and develops bright pink coloration, which makes it a rewarding midground stem or a low-trimmed colorful groundcover.

Propagation Method (Cuttings)

Like other stem plants, kawagoeanum is propagated by cutting the top few centimetres of a stem and planting it straight into the substrate, where new buds and roots emerge from the internodes. Aquatic stem plants take replanting well and regrow their root systems quickly.

Step-by-Step

Cut healthy tops 5–10 cm long from fast-growing stems with clean scissors.
Strip the lowest 2–3 cm of leaves so the buried section stays clean.
Plant each cutting a few centimetres deep, spacing stems apart rather than in one dense bunch.
Leave the trimmed bases in the substrate so lateral buds form and thicken the group.
Because it converts to submersed form within days, expect new pink-tinged growth quickly under good conditions.

Conditions for Healthy Growth

kawagoeanum is a fast grower that benefits from CO2 and responds to higher nutrient, CO2 and light levels with bushier, more branched growth. Strong light brings out the pink-red tones; with CO2 and good fertilization it extends quickly and needs space at the back or middle of the layout.

Trimming & Maintenance

Because it grows fast it needs regular topping. Trim while the lower stems are still healthy — up to about three times — then replant the colorful tops and discard the old stems and roots. Trimming low repeatedly keeps it as a dense, colorful groundcover instead of a tall stem.

Common Challenges

Under weak light or without CO2 the plant grows leggy and loses its pink-red color, and shaded lower leaves drop. Thin crowded clumps, keep light and CO2 strong, and replant fresh tops when the base deteriorates.