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Lichen 101: What You Really Want to Know

Trees need consistent care and maintenance for healthy growth. Right from adequately watering the tree to mulching it properly and pruning it at regular intervals – tree health care involves everything that is required to keep your tree healthy; in the best shape and disease free.

Sometimes in spite of all the care you take, you come across unusual growths on a tree that leave you puzzled. Whether it’s just some mossy residue or more serious symptoms such as alarming lumps and galls, it is important to take immediate action and contact an arborist.

Lichen 101 What You Really Want to Know

One such occurrence our arborists are regularly called to inspect is green growth found on branches and tree trunks. And, in most cases, it’s lichens.

No, this organism is not deadly to your tree, but here is what you should know about this commonly seen tree growth.

What Are Lichens?

Lichens are two-part organisms made up of filamentous fungi and algae with some types of cyanobacteria. They occur together to form one of the most common symbiotic and mutually beneficial relationships.

A symbiotic relationship is one wherein both organisms live together in a mutually beneficial relationship. In the case of lichens, the fungus—which makes up 80% of the lichen—collects moisture and minerals while protecting the algae.

In return, the algae—consisting of chlorophyll—makes food via photosynthesis, which the fungus benefits from as well.

Together, they coexist, creating a conducive environment for each other.

Lichens grow on various kinds of surfaces ranging from tree trunks and branches to rocks and even soil. Being epiphytic in nature, they use surfaces to merely grow on. Lichens appear in colors such as greenish gray, dark brown, yellow, orange, and even black.

Types of Lichens

The three main types of lichens that are seen on trees are crustose, foliose, and fruticose.

Crustose lichens are flat, thin, and closely attached to the surface of the tree. Due to its form, it is almost impossible to extricate them without breaking them.

Foliose lichens are flat but broad and leaf-life. They have an upper and lower surface and are loosely attached to the surface.

Fruticose lichens, on the other hand, are the most complex of the lot. They are shrubby and have a branch-like appearance. They are attached to the surface only at the base.

While foliose and fruticose lichens can be seen with the naked eye, crustose lichens require magnification to be identified.

Lichens and Trees

Lichens grow in areas where they find adequate sunlight and moisture for photosynthesis, be it healthy or unhealthy, young or old trees. For instance, young trees with smooth bark tend to give rise to crustose lichens, but as trees get older, bark develops crevices, which attract foliose and fruticose lichens.

When lichen is seen on unhealthy trees, it is common to think its the reasons behind its deteriorating health, but in reality, the tree’s ill-health is due to other reasons.

The only reason why lichens grow on trees with less foliation is because of the increase in available sunlight.

Trees can also derive benefit from lichens. The decomposition of lichens adds nutrients into the soil which helps trees and other plants in the vicinity, thereby acting as a natural fertilizer.

Lichens can also lead to the formation of organic matter in the crevices of bare rock, which leads to the growth of trees.

Are Lichens Harmful?

While the presence of lichens may lead many to believe a tree is deteriorating, it is untrue. Lichens are not parasites; they don’t extract nutrients from trees and other surfaces they grow on and therefore do not cause any harm.

In fact, lichens are considered to be the best indicators of air pollution. They are highly sensitive to pollution as air pollutants contain sulfur dioxide which prevents the growth of lichens. So, if you have lichens in your area, you are sure to be breathing clean air!

It is due to this characteristic that lichens are used as bioindicators around the world.

Uses and Benefits

While lichens are used as winter food for grazing animals in Arctic regions, they are used by birds and insects for nesting and shelter purposes. This organism also helps in the formation of soil as it is the first to inhabit barren, rocky areas. In fact, it helps in the disintegration of rock stones by forming acids.

Lichens have also been used to create natural dyes for fabrics owing to the fungal component, which makes them a perfect source of pigments.

Many lichens also contain aromatic substances and essential oils, which makes them useful in the perfume industry.

It’s also said to have medicinal properties and many antiseptic creams have originated from lichens.

So, Do I Just Let It Be?

Even though lichens don’t cause harm to trees, it’s better off treated as it isn’t aesthetically pleasing and might also attract tree-infesting insects that lay eggs, which can prove to be detrimental later.

A common way to get rid of lichens on tree trunks is by gently scrubbing the area with a soapy solution. The lichens that are lightly hanging on the bark are likely to come off with this method.

Another way to treat it is with the use of chemical sprays such as copper sulfate and other fungicides that kill the fungal component of the lichen. These sprays should be used in the dormant season; that’s when it’s most effective.

Long-term control measures include regular pruning to make way for better sunlight and air circulation.

Moreover, lichens tend to grow more on slow-growing plants. Therefore, you can aim to fasten the growth process with the use of fertilizers and regular watering to avoid lichens.

Thinking this is an ongoing process you don’t want to take care of yourself. You’re not alone!

Give Mr. Tree a call and we will send our best tree surgeons to inspect your tree and take any necessary corrective measures. Having been in the business of tree care for years, we come with a deep understanding of what it takes to handle all your tree care needs and we’re ready for action no matter what growths we find on your trees.