Creeping Jenny: the golden-green low stem

A bog plant grown underwater

Lysimachia nummularia is a creeping, mat-forming plant from Europe, long grown in gardens as ground cover; the aquarium form is usually the golden cultivar 'Aurea'. Importantly, it is a marginal / bog plant rather than a true aquatic — it grows happily emersed and adapts to being fully submersed, which is how we use it. It can be grown submersed long-term, but it originates from damp ground rather than open water.

Coins of gold and lime

The plant carries rounded, coin-shaped leaves in opposite pairs along low, trailing stems — the species name nummularia means 'like money', for those coin leaves. In the 'Aurea' form the leaves range from lime green to a warm buttery gold. The intensity of that gold is light-driven: strong light brings out the yellow, while in lower light the leaves stay greener. It is grown chiefly for that warm colour, which is unusual among easy plants.

Easy, but colour wants light

Creeping Jenny is undemanding about water chemistry, tolerating soft through hard water, and does not need CO₂. The one lever that matters for its looks is light: give it plenty if you want the gold, and expect greener, softer growth under a dim fixture. It takes up nutrients from both the water column and its roots, so it is not fussy about feeding. Growth is moderate rather than explosive, which makes it easy to keep tidy near the front of the tank.

Parameter	Value
Lighting	Low to high; gold colour needs strong light
CO2	Not required; helps growth and colour
Temperature	18–26°C
pH	6.0–7.5
Hardness	Soft to hard
Fertiliser	Feeds from water column and roots
Substrate	Any; roots along the stem
Growth rate	Moderate
Placement	Foreground to lower midground
Difficulty	Easy

A warm note at the front

Kept trimmed low, it works as a foreground or lower-midground plant, its warm colour standing out against the greens around it and against dark substrate or wood. Left alone, the stems climb and trail, so it can also spill over hardscape. It pairs well with fine-textured greens and with red stems, sitting tonally between them. Because it creeps and roots along the stem, it slowly forms a loose mat rather than a tight carpet.

Cuttings root along the stem

Propagation is easy: cut a length of stem and replant it, or simply lay a trailing shoot on the substrate, where it roots at the leaf nodes. Trimming to keep it low naturally yields plenty of cuttings. As with any fast-rooting creeper, replant the healthiest sections and remove tired growth to keep the patch looking fresh.

Never release it

One caution that is easy to overlook: on land, Lysimachia nummularia is an invasive species in parts of North America, listed as a noxious or prohibited plant in several jurisdictions, because it spreads aggressively in wet ground. That does not make it a problem inside a closed aquarium, but it does mean trimmings and unwanted plants must go in the household waste, never down a drain or into a pond or waterway. Treat disposal as seriously as you would for any vigorous, spreading plant.

More plants in this series

• Staurogyne repens — bushy low green foreground
• Micranthemum umbrosum — bright-green low stem
• Cardinal flower — rounded-leaf low stem
• Brazilian pennywort — round-leaved creeper
• Downoi — compact textured foreground