Common Liverwort
Marchantia polymorpha
Common liverwort is a moss-like weed that colonises damp, poorly drained pots, seedling trays and shaded soil surfaces.
Common liverwort is a primitive, non-flowering plant that forms flat, green, ribbon-like structures called thalli that spread across the surface of damp soil or potting mix. The thallus is lobed and branching, with a slightly leathery texture and a distinct midrib visible down each lobe. Under humid or wet conditions, small umbrella-shaped structures rise on stalks from the thallus surface, these are the reproductive structures that release spores. Liverwort also produces tiny cup-like structures on the surface containing gemmae, small clumps of tissue that splash out during watering or rain and start new plants nearby.
Liverwort has no true roots, stems or leaves. Instead it anchors itself with fine hair-like rhizoids on the underside of the thallus, which draw moisture and nutrients from the top layer of soil or growing media. It thrives in constantly moist, shaded, low-oxygen conditions and is a common problem in nurseries, greenhouses, seedling punnets, garden beds with poor drainage, and around leaking taps or downpipes.
It is widespread across temperate and subtropical parts of Australia, appearing year-round in irrigated or shaded situations but becoming most vigorous during cooler, wetter months such as autumn and winter when soil surfaces stay damp for extended periods.
Management relies on changing the conditions that favour it rather than direct control alone. Improving drainage, reducing overhead watering frequency, increasing light and airflow, and allowing the soil surface to dry between waterings all discourage establishment. In pots and trays, top-dressing with coarse sand or grit reduces surface moisture and makes it harder for gemmae and spores to establish. Removing existing growth by hand or scraping it off before it produces spore-bearing structures helps limit spread.
How to identify
- Flat, green, leaf-like patches spreading across the soil or potting mix surface, often overlapping to form a continuous mat.
- Small umbrella-shaped stalks appearing above the thallus in wet weather, these carry spores that spread the weed further.
- Tiny cup-shaped structures on the thallus surface containing gemmae, which splash out during watering to start new colonies nearby.
- Reduced seedling emergence or vigour where liverwort forms a dense crust over the soil surface, restricting oxygen and water movement to roots.
- Persistent dampness and poor drainage in the affected area, often with algae or moss also present.
Field check: Liverwort is easy to confirm by touch and appearance, it forms a flat, rubbery green sheet rather than upright growth, and lifts away from the soil surface in one piece rather than being rooted like a true plant.
Lookalikes: Liverwort is often confused with moss, which forms a fuzzier, upright, thread-like growth rather than a flat ribbon, and with algae, which forms a slimy, often slippery green film without the lobed, leaf-like structure of liverwort.
