Rotala 'Nanjenshan' Propagation Guide

How to propagate Rotala sp. 'Nanjenshan' (Rotala 'Green') by cuttings — topping the stems, replanting tops, and growing dense bushes under strong light and CO2.

Overview

Rotala sp. 'Nanjenshan', also traded as Rotala 'Green', is a cultivated aquarium stem plant of the rotundifolia group within the genus Rotala (family Lythraceae). Like its parent species Rotala rotundifolia — a common weed of rice paddies and wet places across India, China, Taiwan, Thailand, Laos and Vietnam — it is an undemanding stem plant that develops narrow, lanceolate submerged leaves and thrives wherever it receives sufficient illumination.

Because 'Nanjenshan' is a vegetatively propagated aquarium form rather than a seed-grown wild plant, it is reproduced almost exclusively the way the genus is in cultivation: by cuttings. The notes below draw on the biology and cuttings method documented for Rotala rotundifolia.

Propagation Method (Cuttings)

Rotala is propagated by cuttings. Once a stem reaches a useful length you cut it at an internode and plant the cut end elsewhere; new shoots then sprout from the nodes on the remaining stem. If the parent plant is healthy you can cut away most of it, leaving stems only a few inches high, and those stumps will continue to push out fresh shoots.

Step-by-Step

Select a healthy stem and cut the top 5-10 cm with clean scissors, ideally just above an internode.
Strip the leaves from the lowest 2-3 cm of the cutting so a clean section can be buried.
Plant the stripped end into the substrate, spacing each stem at least half an inch (about 1.5 cm) apart to leave room for side shoots.
Leave the original stem in place — new shoots will sprout from the remaining nodes, multiplying the plant.
Repeat each trimming cycle; tops can be replanted many times before the stand needs renewing with fresh tops.

Conditions for Healthy Growth

Light is essential: the plant can grow in lower light, but 80+ umols of PAR promotes better colouration, with the strongest colour seen at roughly 150-200 umols PAR. Strong lighting can turn the foliage almost wine red. CO2 injection is necessary to achieve higher-density bushes, because CO2 encourages the branching of stem plants that produces the bushy form.

Trimming & Maintenance

Rotala rotundifolia takes well to pruning and forms dense bushes. For the first trim, cut about 4 inches (10 cm) below the final height you want the tops to reach; the cut stems branch and fill in. It can be pruned repeatedly for many cycles before it needs replanting with healthier, newer tops.

Common Challenges

Leggy, sparse stems and bare lower stems usually mean too little light or no CO2 — branching depends on both.
Planting cuttings too tightly chokes side shoots; keep at least half an inch between stems.
Old, repeatedly trimmed stands eventually thin out at the base — restart from fresh healthy tops.