Throughout the year, I often receive calls from concerned individuals about gray, fuzzy growths appearing on plants that seem to be causing harm. The culprit that raises the alarm is usually lichen.

It is a common misconception that lichens are parasites that feed on landscape plants. But lichens are actually not harmful to plants.

Instead, their presence might indicate underlying environmental factors, such as poor air circulation, insufficient sunlight or general plant stress. Addressing these issues can improve the health of the plant, but removing lichens themselves is unnecessary and counterproductive.

Lichens are fascinating organisms formed through a symbiotic relationship between a fungus and an algae or cyanobacterium. This unique partnership allows lichens to thrive on tree bark, rocks and even bare soil in some of the harshest environments on Earth.

Their ability to survive in such diverse conditions is a testament to their resilience and ecological significance.

Lichens come in a wide variety of shapes, sizes and colors, often adding an understated beauty to natural landscapes. They can generally be classified into three main types based on their growth forms: crustose, foliose and fruticose.

Crustose lichens form a thin, crust-like layer that is tightly attached to the surface they grow on. This makes them difficult to distinguish from the bark, rock or other surface beneath them. They are often small and grow in circular or irregular patches.

Crustose lichens come in a wide range of colors that includes gray, green, orange, yellow, white and even black.

These colors are produced by pigments or the lichen’s photosynthetic partners, either algae or cyanobacteria. The colors often serve protective functions, such as shielding the lichen from intense sunlight or ultraviolet radiation.

Unlike crustose lichens, foliose lichens are loosely attached to their supporting structure, allowing their edges to lift away. This creates a three-dimensional, textured appearance and makes them easier to identify.

Foliose lichens are smooth or textured. They can display colors such as green, gray, brown or orange, depending on the species and their photosynthetic partner.

Fruticose lichens are perhaps the most striking, with their shrub-like or branching structures that may grow upright or hang from trees like miniature chandeliers. These types of lichens are found on various surfaces, including tree bark, rocks and soil.

Despite their sometimes mysterious appearance, lichens play a crucial role in ecosystems. Due to their sensitivity to pollutants, they are important bioindicators, providing insights into air quality and environmental health. Lichens also provide shelter and food for different insects and small organisms.

I believe lichens are a remarkable example of the complex and delicate relationships found in the natural world. Far from being a threat, they are a sign of resilience and adaptation. They deserve our appreciation and respect for their ecological contributions and beauty.