Written by Jacob Holmstead, Certified Arborist Serving Portland, OR, and Vancouver, WA

Is Moss bad for trees?

Clients often ask if moss is bad for their trees at Samsara Tree Care, sparking curiosity about the role moss and lichen play in tree health. Often, trees or shrubs with declining health show signs of mosses and lichen clinging to their stems and branches. Although it’s a common belief that Bryophytes and Epiphytes are responsible for tree decline, the reality is quite different—these organisms are rarely the underlying cause of poor tree health.

Moss and lichen are fascinating and beneficial organisms that have adapted to survive in diverse environments across the globe. From Arctic tundras to tropical jungles, and even on oceanic coastlines and in caves, bryophytes and epiphytes have evolved to thrive under extreme conditions.

In the Pacific Northwest, the cool, wet climate provides an ideal environment for these organisms to flourish. You’ll often spot them on tree trunks, branches, rocks, and the forest floor. During dry periods, mosses and lichen go dormant, only to reactivate when moisture returns. This ability to “pause” and “resume” their activity highlights their resilience and adaptability.

Lichens are particularly unique because they form as a result of a symbiotic relationship between green algae and ascomycete fungi. This partnership allows lichens to develop in a wide array of shapes, sizes, and colors. Recent research by Tim Wheeler and colleagues revealed that a third participant—a basidiomycete fungus—also plays a role in this relationship.

In this symbiosis, algae provide nutrients through photosynthesis, while fungi offer the structural framework that houses both organisms. This collaboration enables lichens to survive in environments where other life forms cannot, making them an essential part of many ecosystems.

Beyond their natural beauty, mosses and lichens offer surprising benefits that enhance ecosystems and support both wildlife and human needs. These organisms are used in the production of perfumes, paper products, and even medicinal treatments for burns and cuts. For wildlife, they serve as a food source, and for humans, they offer cultural and commercial value.

Additionally, because mosses and lichens react to air pollutants and heavy particulates, they are often used as indicators of air quality. Their presence can signal clean, healthy air, while their absence may indicate environmental stress or pollution.

At Samsara Tree Care, we believe the answer is “no” for most cases. Mosses and lichens are not parasites. Unlike mistletoe or other parasitic plants, they do not extract nutrients from the tree. Instead, they pull nutrients and moisture directly from the air. Their presence on trees is more aesthetic than harmful, adding texture, color, and character to the tree’s natural architecture.

While moss and lichen are generally harmless, there are specific situations where moss can become problematic, marking an important shift in how we assess its impact. If moss grows too thickly along the trunk and branches, it can block dormant buds from sprouting into new branches. This may hinder the tree’s ability to develop fresh growth.

If you notice a significant buildup of moss, especially on younger trees or trees struggling to grow new branches, it may be wise to remove some of it. Moss removal can be done by hand or with a pressure washer, but it’s crucial to avoid damaging the bark. Bark damage exposes the tree to pests and disease, so care must be taken during removal.

At Samsara Tree Care, our perspective on moss and lichen has shifted over time. Initially, we viewed their presence with skepticism. But as we’ve learned more about their ecological role, we’ve come to appreciate them as beneficial, beautiful additions to trees.

If you’re concerned about the health of your trees, don’t wait—consult with a certified arborist at Samsara Tree Care today for expert advice and a comprehensive tree health assessment. Our team can provide a tree inspection or a detailed arborist report, offering insights into the health of your trees and guidance on whether moss removal is necessary.

For more information or to schedule an inspection, contact Samsara Tree Care—where we’ve grown to love the “mossy stuff” just as much as our clients have.