Lichen on a tree

Just What Are Those Green Spots on My Trees?

Do you have green spots on your trees? This is something that many people have been noticing in their yards lately, and it is quite curious. There are many many reasons why you may have more green spots this year than ever before – and a lot of it has to do with the changing climate. However, it also has to do with the fact that many more trees are coming from the same places, which means that the funguses that cause some of the problems spread much more easily.

Some of the green spots that you have on your tree aren’t any problem at all – they are just natural. In fact, this is probably the greatest majority of the green spots that there are in our area.

Still, there are some problematic green spots that you can have as well. If you think this might be your tree, it is best to reach out to a professional to have them help you determine whether or not you have an issue.

So why are there green spots on your tree – and more importantly, do you need that professional intervention? Let’s have a look:

3. I Have Green Spots on My Trees – What Are They?

Tree with green spots
Credit: Nicholas A. Tonelli
  • Many things manifest as green spots
  • All look similar and some are safe – some aren’t
  • Algae, moss, and lichens are the most common in our area

If you do happen to have green spots on your trees or shrubs, there are three primary culprits: algae, moss, and lichens. These green spots will all grow on the branches of your trees, the trunks, and maybe onto the leaves and roots. It is difficult to tell these three blights apart, but there are some distinct differences in the way they look, how they come to be, and what you have to do with them.

The Royal Horticulture Society provides an outline on how to tell them apart:

Algae: On tree trunks and leaves of evergreen trees and shrubs, algae can be seen as a green, powdery deposit. It is not unattractive on trunks but can make leaves dull and unsightly. The alga Trentepohlia is seen as a vivid orange powdery deposit on tree trunks and branches.

Lichens: Lichens growing on trees and shrubs are mainly grey to green in colour. They may form as crusty patches, leafy mats, or upright branching or hanging growths on the bark or wood.

Moss: Various mosses can grow on the trunks or branches of trees and shrubs. These mosses may form large, coarse, loose, green or yellowish-green tufts, densely matted tufts, or compact green cushions.

If that seems complicated, a professional can help you to determine what you have, and even more importantly, what you can do. Sometimes, you won’t have to do anything unless you do not like the look of the green spots.

2. Why Are There Green Spots on the Trunk of My Tree?

Lichen on a tree
Credit: John Rusk
  • The climate or placement of the tree helps it
  • The weather has allowed it to grow
  • There is a transfer of fungus

If you have green spots on your tree and you can’t tell them apart using the listing above, don’t worry – you aren’t alone. Each of those green organisms can look different, depending on the tree or the yard. You may need to look at the surroundings to narrow down the list even more.

If you have algae on your trees, you have to know that it is rare and could be the sign of an underlying problem. Your tree’s bark may be too moist and that can lead to deeper problems within the tree. Sometimes, the tree will be able to adapt and grow regardless, but it is still something to look at with a professional.

Moss is far more common and can grow in almost any part of the world. Most often, it will grow on trees that have a lot of shade – so trees that have a thicker canopy, trees that are tightly packed together, or trees that are in the shade from other structures like a house or pool. Most often, moss does grow on the north side of the tree, so you can use it for navigation, but not all the time.

According to North Carolina State University, “Lichens increase over time. So older tree have more lichens. Often the lichens will multiply when the tree slows down it’s growth and the canopy becomes less dense. Slow growth and few leaves are not good signs. But it doesn’t mean the lichen is causing the death of the plant. The increase in lichens happens because the tree is dying. Sometimes a cherry tree, apple tree, or azalea becomes covered with lichens. When this happens the tree may be a few years away from death. Of course, every lichen doesn’t mean the plant is declining. Lichens are common on the trunks of large healthy oaks and maples.”

1. Can I Treat Green Spots On My Tree?

Green spots on bark
Credit: Paul VanDerWerf
  • Depends on what causes the green spots
  • If it doesn’t cause harm, don’t do anything
  • Consult with a professional before taking matters into your own hands

Most often, the best thing you can do with your green spots is just to let them be. By trying to do something by yourself, you could be causing more damage. There are some ways to scrape off the green spots, but this often opens the tree up to other infections that are going to harm your tree. If you do have to do something, the best thing you can do is consult a professional.

According to Hunker, “There are also commercial sprays that can be used on the trunk, the leaves and roots of an infected tree. These products are best used at the first signs of an infection and sprayed directly into some of the discoloration that’s found on the affected tree. This may help prevent the infection from spreading further and may help save the tree. However, if a bark is fully rotted through and if the fungus has spread throughout its entire internal system, the tree will not be able to take in water or sprays.”

Tree care is difficult, nor is planting a tree, but it isn’t something that you want to do all by yourself without at least some help from a professional. For daily maintenance and maybe even planting trees, you can do most of it. However, when it comes to the health of your trees, it is best to talk to professionals who can help you out.

At Portland Tree Service, we can help you with all of your tree care needs – and we will bring our own tools. For more information about our services, give us a call today at (503) 941-0922.

Header photo courtesy of Joshua Mayer on Flickr!