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Lichen

Episode #2
Release Date: January 05, 2024

You’ve heard of lichens, but what exactly are they? Let’s explore how to spot them in the landscape and understand what they really are.

Episode Transcript:

JULIE
On this episode of Your Central Florida Yard. Join us for a discussion on lichens. Lichens? You might be saying, what are those? Learn how to recognize lichens in the landscape and what exactly they are doing on your tree, or even a garden bench or fence post.

ANNE
Welcome to your Central Florida Yard, the podcast series where we explore how to successfully garden in the unique climate of Central Florida. Whether you're a seasoned gardener or just starting out, this podcast is for you. So grab your shovel and get ready to dig in. This podcast is brought to you by UF/IFAS Extension Polk County.

JULIE
Earlier this year, I received a call from someone very concerned about this red growth on their oak tree. They were alarmed that a disease was affecting the tree. I asked for some photos to try to identify it. As soon as I saw the photos, I knew what it was. It turned out to be a lichen commonly called a Christmas lichen, Christmas wreath lichen, or also it's known as Baton Rouge lichen. 

In this case, it was found on several branches and probably around a foot long on the branches and several inches wide from what I could see in the photos. This particular lichen is very bright pinkish red in color, and I see how alarming it could be if you don't know what it is. But it turns out it's perfectly harmless. 

ANNE
Okay, so what exactly are lichens? They're really interesting organisms, lots of shapes and sizes, and can be really confusing to people that don't know what they are. So they do come into the office quite a bit. We would consider lichens, epiphytes, not parasites. We talked about epiphytes in our Spanish Moss episode, if you're interested in learning more about other epiphytes, what epiphytes get their nutrients and water from the air and the water that runs over them? 

They're not harmful like parasites that actually take their nutrients from the host plant that they're on. So an example of a parasite would be mistletoe that grows in trees, that actually takes from that tree and will eventually kill the plant.

JULIE
Yeah. So a little bit more about lichens. They actually consist of a fungus and an alga growing together in a mutually beneficial relationship. Pretty cool, right? The fungus gets water and minerals from the air and the material it is growing on, and it actually provides structure and protection for the alga. The algae then provides carbohydrates and vitamins that the fungus needs to grow. 

Nitrogen is acquired from organic material, plant runoff, and even bird dropping. Just an FYI, alga is the singular form and algae is a plural form. So the entire fungus and algae structure are called a thallus. And so the thallus is different structurally from either component. And so it takes actually a microscope to distinguish the fungus from the alga, when you're looking at a lichen. 

ANNE
All right I think it's important to point out, too, that when we hear fungus, it's not necessarily bad. That doesn't mean it's a bad thing. So fungus are actually a group of organisms that are classified as different from plants. So in the case of a lichen, it's an algae and a fungus that have a symbiotic or mutually beneficial relationship to each other. 

So they're helping each other out. And while the lichens themselves are not harmful, there are lichens that can indicate a stressed or declining plant. So just like with Spanish moss, people assume that the Spanish moss is killing the tree. But actually the plant is already declining and that situation only provides what those lichen need to grow. So more sun, maybe more access to nutrients not from the plant itself, but from the environment. 

So in some cases, lichen could be on a stressed plant, but not all cases. And it is important to remember that if you do have lichens growing on tree branches or tree trunks or things like that, you don't want to spray chemicals to remove the lichen or scrub them off in any way. That won't make any difference. And certainly the chemicals could actually harm the plant that it's growing on. 

JULIE
So Anne, what are the benefits of lichens then, if we shouldn't be removing them? What would make us want to leave them? 

ANNE
So lichens can tell us a lot about the environment around us. They're actually beneficial to humans because they're absorbing things in the atmosphere like pollutants. Carbon, sulfur, heavy metals or other pollutants in the atmosphere can be absorbed into that lichen thallus. And then researchers can extract toxins if present and determine the levels that are currently in our atmosphere. 

So that's a pretty cool thing that lichens are doing too. 

JULIE
Yeah, that sounds very beneficial. And so hearing about all these benefits, that's a lot of information to help us like lichens. But I also find their appearance to be interesting as well. 

ANNE
I do too. I think lichens are really attractive. They're such unique forms and everything. Can you explain a little bit about what lichens look like? 

JULIE
Yeah. So there's four basic growth forms of lichens. One form is known as crustose. They're crust-like. And so you're going to find these growing in tight areas against the substrate, so like on the tree or the trunk where they're found. Another is known as squamulose. And so these are clustered in a tight form. They kind of have the appearance of slightly flattened pebble like components to them. 

Another is foliose. And so as it sounds, they're leaflike in appearance. And unlike the other two, these are not tightly bound and have flat sheets of tissue. The fourth basic form is fruticose. It appears as a freestanding tube that are branching. 

ANNE
Lichens can be lots of different colors too. So don't be alarmed if you see something green, red, gray, white, yellow, or even black growing on your plants. 

JULIE
Yeah, and the Christmas lichen that I mentioned earlier is a form of crustose, that type of lichen and it has that reddish pink color. Another example of a lichen is something we call reindeer lichen and strap lichen. And those are both the fruticose forms and I would say reindeer lichen is probably one of my favorite lichens. 

ANNE
Yeah, I like those too. They look really kind of weird when you see them in a natural area, the kind of the little grayish green bumps all along the ground. It kind of looks like alien type of thing, but they are really noticeable if you're out hiking or something and really cool to see. Lichens are really interesting organisms that consist of symbiotic relationships between an algae and a fungus. 

And remember when you see them in the garden, whether on a tree branch or a garden bench, they're not harmful plants and they actually benefit us by absorbing pollutants in the air. So our garden checklist for this episode is to take a closer look and notice different forms, colors, and sizes of lichens, whether in your yard or out in a natural area. 

Share photos with us on social media or send them to us and we can identify them for others and kind of help people learn a little bit more about lichen identification. 

JULIE
For more information on lichens, information and workshops available, contact your local UF/IFAS Extension. All resources from this episode are listed in the show notes. 

Thanks for listening to Your Central Florida Yard. We hope this episode has provided you with valuable insights and tips for your gardening journey in this unique part of the state. Your Central Florida Yard is produced by Anne Yasalonis and Julie Schelb. If you have any questions or suggestions for future episodes, find our contact information in the show notes. 

This podcast is brought to you by the University of Florida's Institute of Food and Agricultural Sciences Extension, an equal opportunity institution. Thank you for listening and as always, happy gardening. 

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Transcribed by J. Bayer-Fermier - 07/12/24 

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