Moss vs. Lichens: Key Differences

Most everyone is familiar with mosses. These low-growing plants have the tendency to coat any surface that remains moist for long periods of time — tree trunks, rocks, hillsides, you name it. What most people are also familiar with are lichens, even if they don’t know it. They tend to grow in the same environments as mosses, often side by side, and are frequently mistaken for mosses themselves. But what are lichens, anyway, and how can you distinguish between these two important types of organisms?

In this article, we’ll highlight the differences between mosses and lichens. We’ll talk about how each grouping of organisms is classified, how their structures differ, and some of the ways you can tell them apart visually.

Structural Differences

When it comes to distinguishing between mosses and lichens, we first need to look at their structures. Mosses are simple plants, falling between algae and vascular plants in terms of complexity. They have no true leaves, stems, or roots, but are capable of long-term survival on land where they can anchor themselves to surfaces and take in water and nutrients via osmosis. While algae, which are protists, can photosynthesize, they tend to be much simpler in structure and most often reside in aquatic environments. Vascular plants, on the other hand, are true plants and have specialized parts like roots, xylem, and phloem for active water and nutrient transport.

Lichens may sometimes look like plants but they are entirely different in terms of their structures. They are essentially compound organisms — the result of symbiotic relationships between fungi, algae, and sometimes bacteria. Not all lichens are green, but due to their algal or bacterial components, all of them can photosynthesize. These internal powerhouses synthesize carbohydrates from sunlight, air, and water to feed themselves and their fungal partners. In return, the fungi, who produce the main body of the organism, protect their photosynthetic partners from the outside world. With a chitinous fungal body to protect them, the algae and bacteria can survive in much dryer terrestrial environments.

Visual Differences

While it is usually quite apparent that mosses are plants, lichens can take on a less familiar and impressive variety of shapes and colors. In many cases, they have a crusty or rubbery texture. Some, like the reindeer lichens (Cladonia sp.) tend to resemble mosses very closely while others, like Usnea and Umbilicaria species, can look much more alien.

Lichens exhibit three primary growth forms: crustose, fruticose, and foliose. Crustose lichens grow very closely to their substrates, resembling a crust, cracking paint, or dried-on soil. They can show off a variety of colors from matte gray to vibrant yellow. Foliose lichens most closely resemble plants. They produce wide, flat bodies that resemble simple leaves and stems that rise just above their substrate. These lichens tend to flake off of the surface they are growing on with little effort. The third type, the fruticose lichens, tends to look the most alien. They often take on a bushy, branching appearance that resembles a coral or bushy moss. Often, this fluffy body is decorated with cups, tubular structures, fine hair-like protrusions, or all of the above They can be strikingly colorful and beautifully complex!

Moss vs. Lichens: Similarities

Like mosses, lichens lack root structures and must rely on osmosis to take in water. Because of this, they favor moist environments and tend to be small and low-growing. Both rely on water to spread their spores during reproduction and oftentimes, they grow side-by-side.

Without the ability to actively transport moisture, both groups of organisms can only grow in accordance with the available rain or water vapor. As local and atmospheric humidity changes, so does the moisture content within their bodies. That means that they are at their best during a long bout of rain, fog, or mist when they have great access to water. During dry spells, when there isn’t enough moisture to sustain growth, both can go entirely dormant. As humidity drops, their bodies can dry out almost completely, suspending their ability to photosynthesize. When moisture returns, they reawaken and begin to grow again. This incredible and complex survival strategy is known as poikilohydry. Their habitats, sometimes similar appearances, and tolerance for drying out are about where the similarities between mosses and lichens end, though!

The photo featured at the top of this post is © Petra Richli/iStock via Getty Images