Propagating Gratiola viscidula by Cuttings

How to propagate Gratiola viscidula, a slow-growing bushy stem plant, by topping and replanting cuttings to build a dense, carpeting fore/midground cushion.

Overview

Gratiola viscidula is a North American stem plant relatively new to the aquarium hobby. Its submersed form has a distinctive, somewhat thorny look, with each stem about 1-2 cm wide. It willingly branches and spreads, forming a very dense fore- to midground cushion that can reach 10+ cm tall but is easily kept low and almost carpeting with regular trimming.

Growth is slow, and under good illumination the bushy tips tighten up. Because the plant branches readily, cuttings are the natural and reliable way to multiply it.

Propagation Method (Cuttings)

Gratiola viscidula is propagated by topping: you cut the upper portion of a healthy stem and replant it, while the remaining base pushes out new side shoots. Over successive trims this turns a few stems into a thick, self-renewing patch.

Step-by-Step

1. Select a healthy, upright stem and snip off the top 5-8 cm with sharp scissors.
2. Strip the leaves from the lowest 2-3 cm of the cutting to expose bare nodes.
3. Plant the bare section 2-3 cm deep into nutrient-rich substrate, spacing cuttings so they fill in into a cushion.
4. Leave the trimmed base in place — it will branch into several new side shoots.
5. Maintain good light and CO2 so the replanted tops root within roughly one to two weeks.

Conditions for Healthy Growth

Provide medium-to-good light and a medium CO2 level (around 6-14 mg/L) to keep growth compact and the cushion dense; weak light makes the bushy form loose and leggy. A nutrient-rich substrate supports its fibrous roots. Although primarily grown submersed in aquariums, it can also be cultivated emersed, which is a robust way to bulk up stock before flooding.

Trimming & Maintenance

Trim roughly every three weeks. Each trim both controls height and doubles as propagation, since every removed top can be replanted and every cut base branches. Regular trimming is what keeps the plant low and almost carpeting rather than tall and open.

Common Challenges

Its slow growth means patience is required — a dense carpet builds over many trim cycles, not overnight. Insufficient light is the most common reason for a thin, stretched stand. Keep the spreading habit in check near smaller neighbours so the cushion does not crowd them out.