With summer in full swing and the foothills of Colorado embraced in balmy (and lately even hotter) temperatures, you’re likely spending more time outside. But the more you’re out around your property, the more you’re noticing crusty patches of varying colors growing on your trees. Is it moss? Fungi? Something else entirely? It’s actually called lichen and while it doesn’t harm the tree, it does indicate tree stress.
Lichen on trees is quite common in Colorado. When you understand more about its growing conditions and what it means for the trees in your yard, the easier it is to make informed decisions about your landscape.
Key Takeaways
- Lichen is a beneficial organism commonly found on trees.
- While lichen is not harmful to the tree itself, the presence of it does indicate tree stress from other causes like drought, pests, or disease.
- Because these symbiote organisms can only thrive in clean environments, they serve as nature’s air quality monitor and confirm excellent air quality when found on your property.
- Removing lichen damages bark and creates disease entry points, so a better treatment approach is to monitor and maintain overall tree health.
- If lichen appears on previously clean trees, consult a Certified Arborist to assess any underlying issues that may be impacting your tree.
What Is Lichen? Understanding Nature’s Unique Partnership
Lichen is unusual in that it represents one of nature’s most successful partnerships – a symbiotic relationship between a fungus and an algae or cyanobacterium, often with additional microorganisms joining the mix. This unique collaboration creates an organism that’s neither plant, animal, nor simple fungus, but something entirely different.
Because lichen is completely self-sustaining, it doesn’t need to take any nutrients from the trees it grows on. This is a crucial point to keep in mind: lichen is not parasitic and therefore is not harming your tree. Unlike mistletoe or other true plant parasites, lichen gets all the nutrients it needs from rainwater and the surrounding air.
Science Behind Lichen Symbiosis
Lichen is the perfect example of a mutually beneficial partnership: each organism provides something the other needs:
- The fungal component creates the structure, gathers the moisture, and provides the “anchoring” ability for the lichen to remain attached to the surface it is growing on.
- The algae or cyanobacteria perform photosynthesis to create food for both partners.
This collaboration is so efficient that lichen can survive in environments where neither organism could exist alone, making them often the first life forms to colonize areas after natural disasters like forest fires.
In Colorado’s challenging mountain environment, this resilience explains why lichen thrives across our diverse elevations and climate zones, from the high alpine tundra down to the lower foothills, where most of our residential properties are located.
Seasonal Patterns and When You’re Most Likely to Notice Lichen
Lichen becomes more noticeable during some seasons than others, but that doesn’t mean it hasn’t been present and slowly growing all year. It can be seen in all four seasons or after storms when the moisture levels are higher.
Lichen activity changes throughout the year, demonstrating their climatic adaptability:
- Summer Growth: Lichen is most active during Colorado’s monsoon season (July-August) when moisture and warmth combine.
- Dormancy: The organism becomes less active in the dry winter months but remains attached.
- Color Changes: Lichen shifts in appearance from gray/brown when dry to green/yellow when moist – becoming more noticeable after precipitation.
Why Lichen Appears on Colorado Trees
The presence of lichen on trees is somewhat paradoxical: the good news is that you have excellent air quality in your area; the less “good” news is that new patches of lichen growing on a tree where none existed before indicates that your tree is already experiencing some form of decline or stress.
Lichen is rarely found on healthy, vigorous trees – not because lichen causes problems, but because healthy trees create conditions that aren’t ideal for lichen establishment and growth.
Environmental Conditions Lichen Loves
Lichen thrives in areas with abundant sunlight and moisture, which is why it’s commonly found in sunny, periodically wet locations throughout the Front Range. Colorado’s climate pattern of intense sunshine combined with afternoon thunderstorms during the summer months creates nearly perfect conditions for lichen growth.
However, lichen also requires good air circulation and clean air quality to flourish. This is why scientists use lichen communities as biological indicators of environmental health and air quality indicators – they simply won’t establish in areas with significant air pollution or contamination.
Lichen’s Connection to Tree Health
When a tree loses vigor due to stress, disease, pest damage, or environmental factors, several changes occur that make it more hospitable to lichen growth:
- Increased Light Penetration: If your tree has experienced sudden leaf loss, branch dieback, or thinning canopy due to stress, more sunlight reaches the bark surface where lichen can establish.
- Slower Bark Growth: Healthy trees continuously shed and renew their outer bark, making it difficult for slow-growing lichen to gain a foothold. Stressed trees have slower bark turnover, providing stable surfaces for lichen colonization.
- Reduced Tree Defenses: Vigorous trees produce compounds and maintain bark characteristics that naturally discourage epiphytic growth (a category of plants and plant-like organisms that grow on the surface of another plant), while declining trees lose some of these protective mechanisms.
Common causes of tree stress in our Jefferson County and Front Range area include:
- Prolonged drought conditions (increasingly common in Colorado)
- Mountain pine beetle and other pest infestations
- Root damage from construction or soil compaction
- Improper pruning that weakens tree structure
- Soil chemistry changes from development or road salt
- Competition from overcrowded plantings
IMPORTANT: Lichen doesn’t cause tree decline, but its sudden appearance often indicates your tree is already stressed. This is your cue to have a Certified Arborist assess what’s really affecting your tree’s health.
Understanding this relationship helps explain why lichen often appears on trees that you thought were healthy. The lichen may be revealing early-stage problems that aren’t yet visible in the tree’s overall appearance, making it an early warning system that you can use to your advantage.
Are There Any Benefits of Lichen?
Surprisingly, lichen can actually be of significant benefit to both our Colorado environment and the broader ecosystem. While it may look somewhat concerning, lichen on trees – and everywhere else they grow – provide valuable services that extend far beyond what most people realize.
Scientific Air Quality Indicator
Lichen serves as nature’s sophisticated air quality monitoring system because it absorbs everything in the environment around it but only thrives when the air quality is clean. This makes it invaluable to scientists studying environmental conditions throughout Colorado.
Scientists rely on lichen communities as some of the best biological indicators of nitrogen and sulfur-based air pollution, making them essential tools for forest health monitoring. In fact, the composition of lichen communities provides early warning signs of improving or deteriorating air quality conditions – often detecting changes before other monitoring methods.
Not only does lichen read air quality measures, it helps contribute to better conditions, too. Lichen converts carbon dioxide to oxygen and actively absorbs pollutants, creating a natural air purification system operating directly on your trees.
For Colorado homeowners, diverse lichen species on your property confirms excellent local air quality –particularly meaningful in our Front Range area where air quality can be impacted by urban development, traffic, and wildfire smoke.
Environmental Benefits Beyond Air Quality
In addition to their notable contributions to air quality, lichens have a surprising number of other benefits.
Practical Uses
Historically, lichen has been used for natural dye production, decoration, and even medicinal purposes. In fact, you might find lichen-derived compounds as ingredients in everyday products like deodorant or toothpaste, thanks to their natural antibiotic properties.
Wildlife Support
Wildlife throughout Colorado forests and foothills are particularly fond of lichen, using its unique material for food, shelter, and nest construction:
- Deer rely on lichens for essential nutrition during harsh Colorado winters when other vegetation is scarce.
- Small mammals and amphibians enjoy lichen as a tasty snack.
- Hummingbirds make use of some of the softer lichen species to create camouflaged nests.
- Lichen provides essential protective cover for beneficial insects.
All that to say: if you’ve noticed lichen growing on your trees, it means your landscape is actively supporting local wildlife and contributing to overall environmental health.
Lichen in Colorado: Types, Colors, and Where They Grow
Colorado hosts an extraordinary diversity of lichen species across its varied landscapes. Over 6% of the earth’s surface is estimated to be covered by lichens, with more than 20,000 different species worldwide. They come in a remarkable variety of colors and shapes, thriving on every continent from humid forests to frozen areas and desert sands.
There are hundreds of lichen species throughout Colorado that exist in practically every environment imaginable, making our state a hotspot for lichen diversity. Many have fascinating common names that reflect their unique appearances, such as:
- Pale-footed horsehair lichen
- Lustrous camouflage lichen
- Salty rock tripe
- Veinless pelt
While these colorful species are found throughout Colorado’s diverse ecosystems, most don’t typically grow on trees – they prefer rocks, soil, and other substrates across our varied terrain.
Common Species of Lichen Found on Colorado Trees
In our community, you’ve likely noticed the distinctive lichen called “old man’s beard,” with its distinct appearance of strings or tassels hanging from tree branches. This species (Usnea spp.) is particularly common on ponderosa pines throughout the Front Range and serves as an excellent example of how lichen adapts to our local tree species.
Other common tree-dwelling lichen types in Colorado include:
- Crustose Lichens: Form gray-green crusty patches tightly attached to bark surfaces
- Foliose Species: Create leaf-like structures with lobed edges on trunk surfaces
- Colorful Varieties: Display yellow, orange, and gray variations on smooth bark trees
- Branching Forms: Shrub-like growth with multiple branching structures
Lichen Grows on More Than Just Trees
You’ll find lichen growing on much more than just trees throughout Colorado – it appears on rocks, fence posts, even tombstones and statues. Lichen simply needs a stable surface to call home. Since lichen is not a plant, it doesn’t have roots that burrow into tree bark. Instead, it stays on the surface, attaching with small fungal threads that don’t penetrate deeply enough to cause damage.
Lichen Vs. Moss: Is It the Same?
Lichen is often confused with moss, partially because some lichens look very similar to some mosses, and partially because it’s often found growing near moss on Colorado trees. However, these are completely different organisms with distinct characteristics.
The two organisms coexist well together in Colorado’s Front Range forests, but understanding their differences helps you better assess what’s growing on your trees and what it means for their health.
Key Differences Between Lichen and Moss
Basic Biology:
- Lichen: Composite organism (fungus + algae partnership)
- Moss: True plant with simple leaves and stems
Physical Structure:
- Lichen: No true roots, stems, or leaves; attaches directly to bark surface
- Moss: Has root-like structures (rhizoids) that anchor into bark crevices
Habitat Preferences:
- Lichen: Loves sunlight and exposed locations
- Moss: Prefers shady, moist areas with less direct sun
Growth Characteristics:
- Lichen: Extremely slow growth (one to three millimeters per year); crusty, leafy, or branching forms
- Moss: Faster growth; soft, cushion-like or carpet-like mats
Moisture Needs:
- Lichen: Gets moisture from air and rain; survives dry periods
- Moss: Requires consistent moisture; indicates persistently damp conditions
The “Reindeer Moss” Exception
“Reindeer moss” or “caribou moss” is actually a lichen – not moss at all. This commonly misnamed organism grows in Colorado’s higher elevations and demonstrates how even common names can be misleading about what we’re observing in nature.
What This Means for Colorado Tree Health
When found together on trees, both organisms often indicate stress.
Lichen presence suggests:
- Increased light from canopy thinning
- Slower bark growth allowing colonization
- Good air quality in the area
Moss presence indicates:
- Consistently moist bark conditions
- Reduced air circulation
- Possible drainage or humidity issues
Bottom line: If you’re seeing what appears to be moss in sunny locations on your Colorado trees, it’s likely lichen – which suggests your tree may need professional assessment for underlying health issues rather than moisture management.
Should you Remove Lichen from Your Trees?
Lichen should not be removed from trees as removing it does more harm than good. This is one of the most important points to understand about lichen management. Since the lichen is not hurting your trees, there’s simply no compelling reason to remove it – besides, attempting removal can actually create serious problems for tree health.
Why Removal Isn’t Recommended
Physical removal attempts cause significant problems, such as:
- Causes Bark Damage from Scraping: Lichen adheres tightly to bark surfaces, making removal without bark damage nearly impossible
- Creates Disease Entry Points: Not only does scraping lichen harm and remove bark layers, this damage provides pathways for fungi, bacteria, and pests to enter the tree
- Removes Beneficial Organisms: Lichen contributes to ecosystem health and biodiversity on your property
- Provides Temporary Results: Lichen will return if the underlying tree stress conditions remain favorable for growth
Ultimately, an attempt to remove lichen usually results in severe bark injury, which just causes unnecessary stress and damage to the tree.
Frequently Asked Questions About Lichen on Trees in Colorado
Can lichen spread from one tree to another?
Lichen spreads through airborne spores, but it only establishes where conditions are favorable. If lichen appears on multiple trees, it usually indicates similar stress conditions affecting several trees rather than direct transmission.
What Colorado tree species are most prone to lichen growth?
Aspen, ponderosa pine, and other trees with textured bark in our area commonly host lichen. However, lichen preference depends more on tree health and environmental conditions than species.
How quickly does lichen grow on trees in Colorado?
Lichen growth is extremely slow, typically expanding only 1-3mm per year. If you’re noticing lichen for the first time, it may have been developing for several years, suggesting your tree’s decline began earlier than you realized.
Should I be concerned if lichen suddenly appears on my healthy-looking tree?
Yes. Sudden lichen appearance often indicates early tree stress that isn’t yet visible in the canopy. This is an ideal time for an arborist inspection to identify and address problems before they become severe.
Are there any benefits to having lichen on my property?
Absolutely! Lichen indicates good air quality, supports local wildlife, and contributes to ecosystem diversity. The goal isn’t to eliminate lichen but to ensure your trees are healthy enough to support both themselves and these beneficial organisms.
Worried About Lichen on Your Colorado Trees? LAM Tree Service Can Help
Discovering lichen on your Colorado trees doesn’t need to cause panic, but it shouldn’t be ignored either. While these fascinating organisms are beneficial to our ecosystem and indicate clean air quality in the beautiful foothills, their presence can signal that your trees need professional attention.
Contact LAM Tree at 303-502-2188 to schedule your tree health assessment. With nearly 50 years of experience caring for trees throughout Jefferson County and the Front Range, we’ll help you maintain a healthy, beautiful landscape that benefits both your property and our local ecosystem.
