Some Trees Glow Under UV Light (And Why That Feels Like Magic)

I was editing my old post about neon fish that glow (GloFish if you want to check it out) and I felt nostalgic again about glowing things. I know I’ve talked about it before, but I really love glow-in-the-dark things. I blame my dad for always giving us GloSticks on holidays and then peppering my room with those glow-in-the-dark stars.

I was thinking about other things that glow and realized a lot of people didn’t know you could walk in the dark hush of a wooded trail, flick on a UV flashlight, point it at an ordinary piece of bark on a tree, and suddenly the tree glows back at you in ghost-green.

Technically, this is a glow the human eye was never meant to see, but was there all along.
When I found out about this years ago it made me wonder how many other secret wavelengths the world keeps folded behind our everyday vision.

Some trees, or more specifically the woods within them, fluoresce under ultraviolet light. Scientists online call it a photonic reaction, a shift in wavelength, or a quirk of plant chemistry. But when you stand there in the dark, watching a beam of purple light turn a dead branch into something neon and alive, it doesn’t feel like plain chemistry, it feels like magic.
It’s the quiet kind of magic that nature never brags about (per usual), so I’m here to blow up its spot and sing its praise to you.

The Forest Has More Light Than Your Eyes Can See

I’ve mentioned before that our vision is painfully small, and we see just a tiny sliver of electromagnetic energy we call “visible light.” Bees see colors we don’t, birds see patterns on feathers invisible to us, salmon can sense wavelengths hidden below our threshold, and I think it was some sort of shrimp that holds the world record for how many colors it can see.

Somehow we tend to forget that plants also live in wavelengths we’ll never naturally witness. Trees like to stand there all inconspicuous so we don’t always give them the credit they’re due. Except me…I prattle on endlessly about how amazing they are. Inside the grain of certain woods like Black Locust, Osage Orange, Mulberry, and a scattering of others, exist compounds that absorb UV light and re-emit it as visible green or yellow.

This is fluorescence at its most basic where light goes in as one thing, then leaves as something stranger and brighter.

Under the sun, the effect is muted, and under a forest canopy it’s completely invisible.
But under UV light, suddenly the tree glows.

From what I can find online it’s not a glow like the pulsing of a firefly or bioluminescent plankton. It doesn’t seem to be like anything that evolved to glow on purpose. No, this glow is more of a happy accident of chemistry. A quirk in the wood’s molecular makeup has the side-effect of protective compounds that protect the tree from UV radiation, fungi, insects, and even decay.

Trees, in their quiet resilience, grew colorful invisible shields against the horrors of nature. Us, in our curiosity, found out some shields shimmer in the dark.

Science In a Way That Doesn’t Kill the Magic

I don’t want to kill the magic for you (or me), so I’m going to explain the why, but just know that doesn’t make anything less magical. If anything, it’s more magical because it’s crazy how much had to come together to make this possible.

Wood contains naturally fluorescent molecules. Lignin, flavonoids, tannins (yes really, that’s why oak-aged wines have more tannin), phenolic compounds, each reacts to UV differently. Some are stable, while some glow green-gold, while yet others burst with lemon-yellow fluorescence.

UV light excites some of these molecules. Think of UV as a ripple in a pond that wakes something sleeping in the wood. They release that energy they produce from the shock as visible light. Green and yellow are common, but people have documented even blue-white in rare cases.

It’s like discovering that the world has been adding another layer of aging to your wine your whole life, but you’ve only ever been looking at the swirl in the glass, not tasting it yet.

The Trees That Glow

Not every tree glows, sadly for me, but a surprising handful do even when they look utterly ordinary during the day.

Some of the best-known “luminous” woods might be in your backyard right now. Black Locust glows a bright, almost electric yellow-green. Its fluorescence is so distinct that woodworkers use it as an identification test.

Osage Orange has one of the strongest glows in the plant kingdom and shines a vivid neon yellow under UV, like the tree swallowed sunlight and never let it go.

Mulberry (especially older heartwood) gives off a warm greenish-yellow flare under UV, soft and gentle, but unmistakable. These are the trees right in my backyard I like looking at at night.

Ailanthus (Tree of Heaven) sometimes shows patchy fluorescence in the inner wood so you might need to look at a log or some dead trees to see it well.

Boxelder & Maple (certain specimens) sometimes show that the sapwood can glow, depending on age and fungal interactions.

Spalted woods not from the tree itself, but from fungal patterns inside the grain glow wildly, unpredictably, and take-your-breath-away-beautifully.

Most of these trees aren’t rare or hard to find. You could be walking past one every day for a decade and never know it was hiding a secret until you shined the right light at it. Sometimes we miss so much of the world because we forget to ask what lies outside our narrow spectrum.

Fluorescence Feels Like Magic (Even Though It’s Just Physics)

If you’ve read my work before then you know I have an obsession with physics and think it’s magical no matter what you call it. I’m also a crazy plant lady so anything to do with trees or growing things I’m going to explore every aspect of.

We don’t really go into forests to learn most of the time, we go to regulate our nervous systems that have been fried to all hell thanks to social media and our modern life. I like to go because something in me still instinctively believes that trees hold old truths that are older than our cities, older than our fears, older than the version of ourselves we show the world.

When you see a tree glow under UV light, it taps into something primal and it’s proof that nature doesn’t need our permission to be extraordinary

A glow that serves no evolutionary advantage, no survival purpose, is beautiful to me. Sort of like the universe left a hidden watermark behind.

Grab yourself a UV light and walk into a forest at night. Shine the light on the ground first (bark sometimes gets in the way of this, and fallen branches or trees are more exposed), and marvel at the wonders of life and light.

When you walk through a nighttime forest holding a black light, you’re asking, “what am I not seeing?”

And the glowing bark tells you, “almost everything.”

Science tells us that we’re built to experience only a fraction of reality and the world around us should humble our assumptions that we know anything at all.

When a tree lights up under UV, it forces us to confront the uncomfortable truth that the world is full of light your eyes were never built to see and you’ve been walking blind in a glowing universe.

The forest hides a language of light under its skin, one that only appears when approached at night, with curiosity instead of conquest. You have to feed the tree some light to have it give some to you in return. It’s a delicate balancing act, one offering leads to another. What you give out comes back to you.

Nature keeps secrets until we learn the right way to look.

Trees don’t glow for us and they never cared if we saw their quiet luminescence.
But the moment you witness it, the instant a beam of UV light turns bark into something that looks alive with hidden fire, you realize the universe is always more complicated, more generous, and more luminous than you thought.

You’re not discovering magic in that moment, you’re just remembering it. The world is full of wavelengths waiting for the right eyes and you’re finally learning how to look.