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Riccia spp.

crystalworts

Ricciaceae Cosmopolitan (all continents)

Native to North America

SunFull Sun – Part Shade

Overview

Riccia spp. is a large, cosmopolitan genus of thalloid liverworts in the family Ricciaceae, with well over 100 species growing on damp soil, mud, rock, and, in a few species, on or below water. Plants lack stems and leaves; instead each forms a flat, forking green thallus that branches in a Y pattern and often arranges into rounded rosettes 0.4-1.5 inches (1-4 cm) across on bare ground. Each thallus lobe is 1-4 mm wide with a central groove along the upper surface and thread-like rhizoids anchoring the lower surface to the substrate. Colour ranges from bright green to gray-green, sometimes flushed reddish in strong light or drought. The aquatic species R. fluitans, sold as crystalwort, forms tangled floating or submerged masses with no rhizoids and is widely used in aquariums. Reproduction is by spores formed inside the thallus and by fragmentation. Terrestrial species often appear after rain on pond margins, fallow fields, and paths, then shrink or die back as the soil dries. As non-vascular plants, they have no true roots and take up water across the whole surface.

Native Range

Riccia spp. is cosmopolitan, found on every continent except the deep polar interiors, and is well represented in temperate, Mediterranean, and tropical regions. Species grow on seasonally damp soil, mud, rock, and fresh water. The aquatic R. fluitans occurs across Europe, Asia, the Americas, and Africa.

Suggested Uses

Aquatic R. fluitans, sold as crystalwort, is used in aquariums as a floating cover or a tied-down carpet that shelters fry and small invertebrates. Terrestrial species are studied in soil and bryophyte ecology. Both forms add to the ground and water layers of naturalistic plantings.

How to Identify

Look for flat, forking green thalli that branch in a Y pattern, often forming small rosettes on damp bare soil, each lobe 1-4 mm wide with a groove down the upper surface. There are no stems or true leaves. The floating, rhizoid-free tangled masses of R. fluitans in still water identify the aquatic species.

Appearance

Colors

Foliage Colors

green

gray green

Fall Foliage Colors

no change

Bloom Information

Liverworts do not flower. Riccia spp. reproduces by spores formed within the thallus and released as the tissue decays, mainly after damp periods, along with vegetative fragmentation. Terrestrial species are most visible in cool, wet seasons.

Detailed Descriptions

Foliage Description

bright green to gray-green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 2-8 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Care & Maintenance

Care Guide

Terrestrial Riccia spp. species grow without cultivation on consistently damp, open soil in sun to partial shade and shrink as the surface dries. They need no feeding and tolerate a wide soil pH. The aquatic R. fluitans grows in still or slow fresh water and is kept in aquariums, where it is often tied to wood or mesh to form a green carpet under bright light. Soft, slightly acidic to neutral water and added carbon dioxide speed its growth. Terrestrial colonies are short-lived once their soil dries out.

Pruning

Liverworts are not pruned. Aquatic R. fluitans mats can be thinned by hand or trimmed to keep an even carpet and to stop lower layers from shading out. Detached fragments settle onto new surfaces and start fresh growth.