Why Does Lichen Glow Under UV Light? The Hidden Fluorescent World of Lichens

Lichen has always fascinated me. Ever since I was a small child there was something intriguing about lichen, I just couldn’t put my finger on what it was. It comes in a variety of colours and shapes, some look like tiny delicate flowers (they are not flowers), others look like bizarre coral (they are not coral), and others look like an unsightly mess. 

Lichen seems to grow in some of the most inhospitable, unlikely, and sometimes unbelievable places. Lichens are a pioneer species, often colonising a barren rock somewhere, paving the way for moss and eventually higher vascular plants to start growing. 

Different lichens 

When I was younger there were a few hills that were covered in old abandoned mines. Very little grew in these places as the top soil was gone and they were just rocks and sub soil that had been dug up by hand a hundred or so years ago in gold rush times. Some of these places were covered in thick beds of lichen. I used to scrape some of this off and take it home to bury in the vegetable garden. I figured it had probably liberated some of the rock minerals that may be useful for my vegetables. Now I am older I think I was onto something, on the other hand it may have contained high concentrations of heavy metals and other toxins, I will never know either way.

Lichen often slowly dissolves the rock they are growing on and releases minerals that were locked up and other organisms can use them. Some types can also absorb heavy metals and other toxins and can be used in bioremediation. Different types of lichen grow on the trunks of different trees. For years there has been debate among horticulturists whether or not lichen is harmless to apple trees or if after the lichen reaches a certain density that it can cause any issues.

Some types of lichen are extremely slow growing, while others seem to almost grow while you are watching them. Some can take extreme heat and dry, others can be frozen solid for months with no ill effects. Some lichens are simple to grow, some people might say they are almost impossible to kill. They can be hot glued onto surfaces or even mashed up and painted on to colonise a larger area quickly. Some people paint them onto gates and artworks to give a new creation an aged and distinguished look. I have seen some growing in interesting low maintenance terrariums. Yet you won’t often find lichen for sale in garden shops or online.

Another fascinating thing about lichen is that they aren’t one organism, they are two or more. Lichen is a combination of fungi and algae living in symbiosis, with each organism benefitting from the other. The way they reproduce and disperse can be rather bizarre and intricate, but I am not going to talk about any of that in this post.

As I said, lichen is fascinating, but it gets better. So much better, and that is what I want to talk about in this post.

Lichen glows in the dark but it isn't bioluminescent. 

If you turn out the lights lichen won't glow, they are dark just like everything else. Nothing to see here, move on, they are boring, go do something else. Put lichen under an ultraviolet light and it is an entirely different story.

Most lichens will fluoresce under ultra violet light, different types will be different colours and different intensities. Some are pretty uninteresting, they kind of glow a little. 

Others glow bright orange, or bright green, or any number of other incredible intense colours. Some lichens have one part that is one colour and other parts that glow another colour, others will have one part that glows and other parts that do not glow.

Unfortunately the camera didn't capture it properly; this lichen glowed bright orange under UV light

 
Some types glow very bright under UV light and are incredible to see. These lichens tend to fluoresce under UV light alive or dead. This means you can plant out a terrarium with these more impressive lichens and even if the conditions are not to their liking and they all die they will still look unbelievable under a black light. 

The lichen on the right fluoresced orange under UV light, although the camera failed to capture the effect

Another fun thing that can be done is to set up an enclosure for something else that glows under UV light, and include different lichens.

Scorpions fluoresce under UV light, they look amazing and I am unable to capture this in a photo. I would not leave a UV light on them the all the time as over time they lose some of their glow and they aren’t really fond of UV light. Putting the UV light on every now and again when you really want to show them off is fine.

If there are lichens that fluoresce bright yellow or orange or green, as well as a scorpion, the enclosure can take on a look that is impossible to describe but is a sight to behold. 

All scorpions have a sting, but none of the Australian scorpions are deadly to people. Some species are certainly grumpier than others, some are more laid back while others are very fast, and some species are far easier to raise than others, so not all are suitable for beginners.

Scorpions are a fascinating animal, they give birth to live young and the female carries the young on her back for some time. Another interesting thing is that adults and young of many species fluoresce different colours under ultra violet light. 

Scorpions shed their skin to grow. I have an exoskeleton from a baby scorpion I had that shed its skin in the year 1999 or 2000, this will still fluoresce when I shine a black light on it. I think that is absolutely remarkable after all this time. If I kept a black light on it all the time it would eventually grow dim and lose its glow, but still glowing after more than twenty years is just incredible.

Baby scorpion exoskeleton 

The same scorpion exoskeleton under UV light 

The more I learn about lichen, the more fascinating they become.  They help create soil from bare rock, survive in places where few other organisms can live, and under ultraviolet light they reveal a hidden world of colour that most people never notice.  Next time you walk past a patch of lichen on a fence post, rock, or tree trunk, take a closer look.  There may be far more going on than first meets the eye.

Ultra Violet torch

Recently I bought a small UV torch.  Mostly because I want to look for scorpions, but also because a lot of things look incredible under ultra violet light.  

While I have no way to measure or confirm this for myself (and have to go off what it said on the order spec sheet) this torch emits light in the range of 365nm 395nm.  

Anything below 400nm is often referred to as invisible, but that isn’t strictly true.  In small torches like this there is always a trailing off of light to the edge of the visible spectrum.  The 365 emits a dull bluish light that is almost invisible to the human eye.  The 395 emits a blue purple light that is more easily seen by the human eye.  

If it only emitted invisible light I would not know if my torch was ever working, so I find that the little visible light they produce is a good thing.  This little torch runs off three AAA batteries and can make things glow intensely even from a reasonable distance.

Parts of corn stalks fluoresce under UV light 

There are a bunch of things around the house that glow under UV light.  Some plastics glow, while others do not.  I can't work out by looking at them which will and which won't.  Interestingly some white paper glows intensely, and other white paper does not.  Some fabrics glow, while others do not.  Under UV light my daughters' room looks somewhat like what I imagine a fairy princess rave party would look like.

Some clear plastics glow, some white ones glow, and some of the dark colours glow.  Below are some photos of things under UV light as well as under normal light for comparison.  

I can't take photos that really look the same as the UV light looks, my phone alters some of the photos and makes them less bright, but this gives you a decent idea of what we are seeing.

A plastic jewel

Some plastics glow, but not others

The plastic container on the lower shelf looks the same but did not glow

My little pony under UV light

My little pony under normal light

This glows a lot more in real life

The same bottle 

Some foods also glow under UV light.  Some things I would have guessed, such as milk, while others took me by surprise.

Honey under UV light looks cloudy

The same jar of honey under normal light

Peanut butter under UV light

Peanut butter under normal light

Ripe bananas under UV light - not a great photo

The same bananas under normal light

White sprinkles glow

I took the kids for a quick walk around the yard to see what would glow under UV light.  We found something under a log that glowed which I think was eggs of something.    

One thing I found interesting is that some spider webs glowed.  No other spider webs glowed, so I think this one had an egg sack under it.  Once the weather warms up and more things are active I would like to see if all spider egg sacks glow, or if it just some species.  I have a feeling that most do not glow.

This spider web glowed, most others do not

As we were walking past the guinea pig hutch something glowed brightly.  

I had a closer look and it was part of a corn stalk.  I wasn't sure if it was due to guinea pig urine, or if corn stalks normally glow under ultra violet light.  

I noticed something in the guinea pig house glowed brightly

This photo does not show the colour, but the corn stalk was bright yellow/green

Glowing corn stalk under ultraviolet light

I still have some corn in the garden that is standing from last season, so we went to have a look at it.  To my surprise, parts of the corn stalks glowed green/yellow, other parts glowed bright blue.  Some of the corn stalks glow intensely under UV light.  I looked on the internet and have not been able to find any other mention of corn stalks glowing under UV light.

To be honest, I thought the corn looked a bit creepy under UV light.  Blair witch style creepy...

I am interested to see if corn stalks glow when they are alive and growing, or if it is only once they are dead.  It may be that there is some fungus or something breaking down the dead stalks that makes them glow.  I don't know yet but I plan to find out in Summer when I have new corn plants growing.  

Corn glowing under ultraviolet light

My photos don't do it justice

I need to look around and see what else glows under ultraviolet light and take some photos.  I really should also put up a blog post of scorpions under ultra violet light because they look incredible.