Propagating Rotala sp. 'Bonsai'

How to propagate the compact small-leaved Rotala sp. 'Bonsai' by topping and replanting stem cuttings to build dense, tree-like midground clumps.

Overview

Rotala sp. 'Bonsai' is a compact cultivar in the Rotala rotundifolia group, a flowering stem plant of the family Lythraceae native to wet places across India, China, Taiwan, Thailand, Laos and Vietnam. Its thick, opposite, oval leaves recall a miniature tree's foliage, and it grows more slowly and densely than typical rotalas, developing bronze-red tones in good light.

Like the rest of the group it is propagated by cuttings. Because it stays short and bushy, repeated topping turns a single stem into a tight, tree-like midground clump.

Propagation Method

Propagate by topping. Cut the top of a healthy stem and replant it as a new plant; the rooted base then branches into several side shoots. Rotala is among the easier stem plants to propagate this way, and 'Bonsai' rewards the technique with especially dense, compact regrowth.

Step-by-Step

Select sturdy, well-formed stems and cut the top few centimetres with sharp scissors.
Remove the lowest leaf pair from each cutting to expose a clean node.
Insert the cuttings into nutrient-rich substrate with the bare node buried.
Leave the rooted bases to branch and thicken the original clump.
Provide good light to keep new growth compact and bronze-tinted.
Top again each time stems gain height to maintain the bonsai-like density.

Conditions for Healthy Growth

As a rotundifolia-type plant it is undemanding but light-dependent: too little light causes lower leaf loss and a leggy habit. Good light plus nutrients brings out the bronze-red tones and keeps internodes short; CO2 and a nutrient-rich substrate support steady, compact growth even though 'Bonsai' is slower than its relatives.

Light: medium to high to keep growth compact and coloured.
CO2: beneficial for dense, even growth and best colour.
Nutrients: regular dosing with a nutrient-rich substrate.
Temperature: standard tropical range suits it well.

Trimming & Maintenance

Trim regularly to maintain the compact, tree-like form. Topping keeps the clump dense and supplies a steady stream of cuttings for propagation. Thin overcrowded stems occasionally so light reaches the lower leaves and the base stays leafy.

Common Challenges

Stretching and bare lower stems signal too little light, and pale growth points to thin nutrients. Increase light and feeding to restore compact, bronze-red growth, and top regularly so the clump does not open up and lose its tree-like outline.