Propagating Ludwigia atropurpurea (Dark-purple Ludwigia)

How to propagate the dark purple-red Ludwigia atropurpurea by cuttings and topping, and how high light, CO2 and iron deepen its purple coloration in a planted background.

Overview

Ludwigia atropurpurea is a stem plant of the family Onagraceae prized for very dark purple-red foliage under strong light and good nutrition. It grows upright as a background or mid-ground accent and, like its red ludwigia relatives, only shows its deepest color when light, CO2 and fertilization are all in balance.

Propagation Method

It branches willingly and is propagated by cuttings and topping. Cutting the top of a stem yields a replantable cutting while the base responds by pushing new side shoots, so topping both multiplies stems and builds a denser purple group.

Step-by-Step

Cut the stem at a node below the height you want, staggering cuts across the group for a slope.
Take a 5–10 cm top cutting and strip the lower leaves to expose a clean node.
Plant the bare node into nutrient-rich substrate and let it anchor.
Keep the topped base; side shoots emerge at the cut and can be split off later.
Trim away any outlying shoots that break the slope to keep tidy clusters.

Conditions for Healthy Growth

Purple intensity rises with light: about 70–80 umols PAR gives good color and high light (80 umols+) also drives more side shoots. At least 10 ppm CO2 improves color and branching, with roughly 30 ppm suiting most demanding reds. Iron and balanced nutrients in the column or substrate sustain the dark pigment.

Trimming & Maintenance

Trim about every 7–10 days. Repeated pruning at the node thickens the bush as the base branches, and every removed top is a fresh plant. Stagger the cutting height to keep a layered purple background.

Common Challenges

Color loss: low light, CO2 or iron turns foliage green instead of deep purple.
Leggy growth: too little light stretches stems and thins the lower leaves.
Import melt: emersed-grown stems may shed leaves before adapting to submersed purple growth.