Cultivating lichen indoors represents a unique challenge because these fascinating organisms are not plants but composite life forms, known as a symbiosis. This association pairs a fungus (mycobiont) with a photosynthetic partner (photobiont), typically an alga or cyanobacterium. Unlike common houseplants, lichen growth is extremely slow, requiring the replication of a very specific, stable microclimate to maintain the delicate balance between the two partners.
Understanding the Unique Requirements of Lichen
The primary difficulty in growing lichen stems from their poikilohydric nature; they cannot regulate their own moisture content and become metabolically active only when wet. When hydrated, the photobiont performs photosynthesis, producing sugars that feed the mycobiont, which forms the protective structure, or thallus. Lichens have no roots and absorb all necessary moisture and trace minerals directly from the surrounding air. This dependence on atmospheric input makes them highly sensitive to air quality, often leading to their use as biological indicators of pollution. The growth rate for most species is measured in mere millimeters per year, demanding a commitment to long-term, stable conditions.
Sourcing and Preparing Lichen Samples
Acquiring lichen samples must be done responsibly to protect natural ecosystems. The most ethical method is to purchase live lichen from specialized suppliers who cultivate or sustainably harvest it for botanical use. These suppliers often provide various growth forms, such as fruticose (shrubby), foliose (leafy), or crustose (crust-like). If ethical wild collection is permitted, only take samples from fallen branches or material about to be destroyed, such as wood destined for a fireplace. Never strip lichen from living trees or protected areas.
Initial preparation involves gently cleaning the collected material and ensuring the lichen is securely mounted onto its new substrate. If the lichen is already on a small piece of bark or rock, simply transfer the entire unit. For samples that need remounting, a non-toxic, biodegradable adhesive, such as plant seed mucilage or simple white glue, can temporarily secure the thallus to an inert surface. Before placing the sample in its final enclosure, rehydrate it by lightly misting it with distilled or rainwater, allowing it to become pliable.
Establishing the Optimal Indoor Environment
The most effective way to mimic the natural microclimate is by using a sealed or semi-sealed enclosure that maintains high humidity. The container prevents rapid moisture loss and stabilizes the environment, which is paramount for this poikilohydric organism. The substrate should be non-nutritive and well-drained, consisting of inert materials like porous rock, lava stone, clean bark, or coarse sand and gravel. Avoid standard potting soil or any material that could decompose quickly and generate excess organic nutrients, which encourages competing fungi and mold.
Lichen requires light for photosynthesis, but direct, intense sunlight causes desiccation and heat stress. Place the enclosure where it receives bright, indirect light, such as an east-facing window, or use low-intensity artificial lighting. A full-spectrum LED grow light set on a timer for 10 to 12 hours daily works well, provided it is kept far enough away to prevent heat buildup. Maintaining a consistent relative humidity level, ideally between 70% and 90%, encourages the lichen to remain physiologically active, which correlates directly with growth.
Long-Term Care and Monitoring
Ongoing maintenance focuses on stability and preventing desiccation and mold growth. Water the lichen by misting the thallus and enclosure walls with chlorine-free water, such as distilled or collected rainwater, to avoid the accumulation of tap water minerals. The goal is to hydrate the lichen until it is soft and green, but never soak it or leave standing water on the thallus surface, as excessive wetness suppresses photosynthesis and promotes rot. Misting every few days to a week is a common starting point, depending on the enclosure’s seal.
Temperature stability is important, and a range between 18°C and 25°C (64°F–78°F) is well-tolerated. Air circulation is particularly important in a high-humidity environment to prevent the colonization of mold or pathogenic fungi. If using a closed terrarium, open the lid for a few minutes daily or several times a week to exchange the air and prevent stale conditions. If you notice a white or grey fuzzy growth, which is likely mold, increase the ventilation immediately and reduce misting frequency.