A Houseplant That Glows Without a Light Bulb

It looks like an ordinary white petunia during the day.

Turn out the lights and the plant changes.

Its flowers and leaves give off a soft green glow, with the newest growth shining brightest. There is no bulb hidden in the pot, no battery to replace, and nothing to plug into the wall.

The plant is producing the light itself.

And this isn’t something confined to a laboratory.

Light Bio, an Idaho company, sells the Firefly Petunia to home gardeners. The plant costs about $29, cleared a U.S. Department of Agriculture review, and its first commercial run of 50,000 plants sold out.

The trick that makes it glow came from a mushroom.

Researchers borrowed genes involved in light production from Neonothopanus nambi, a bioluminescent fungus. Those genes worked in a petunia because mushrooms and plants share an important bit of chemistry.

The petunia was already making the fuel needed to produce the light.

Scientists essentially gave it the machinery to use it.

The Fuel Was Already There

The key is caffeic acid.

Ordinary plants naturally produce caffeic acid as part of the chemical processes that build and strengthen their cell walls.

The glowing fungus uses that same compound in its bioluminescent system.

By adding the right fungal genes to the petunia, researchers gave the plant enzymes that can turn chemicals it already produces into light.

That is why the Firefly Petunia doesn’t need owners to continually add some unusual chemical to the soil.

It grows much like a petunia because it is one.

But as it grows, some of its normal chemistry also feeds a light-producing reaction.

The result is continuous bioluminescence.

The plant doesn’t have to sit under a lamp during the day to charge up for the evening. It doesn’t need a special light treatment before guests arrive. As long as the plant is alive and its biological processes are running, it can produce light.

The glow isn’t equally strong across the entire plant.

New growth is brightest.

Developing buds, flowers, and fresh leaves can glow more strongly than older foliage because those actively growing parts of the plant have more of the chemical activity involved in the process.

That gives the plant a somewhat different appearance as it grows.

The newest portions announce themselves after dark.

Another Glowing Plant Works Very Differently

Researchers at South China Agricultural University have also demonstrated glowing houseplants, but they took almost the opposite approach.

Instead of genetically changing a plant to manufacture light, the researchers used phosphor particles.

Their work, published in the journal Matter, involved injecting the particles into common succulent plants.

The basic idea will be familiar to anyone who has owned a glow-in-the-dark toy.

Expose the material to light, and it stores some of that energy. Put it in darkness, and it slowly releases the energy as visible light.

The researchers could charge the succulents for a few minutes using sunlight or an LED.

Afterward, the plants glowed for up to two hours.

They also weren’t limited to the green associated with many naturally bioluminescent organisms. The researchers produced plants that glowed blue, red, green, and violet.

The team went beyond a single glowing plant.

Researchers assembled 56 of the treated succulents into a wall and charged them with light.

The resulting display produced enough illumination for someone nearby to read a book.

That suggests possibilities beyond putting an unusual plant on a windowsill.

But the succulent and the Firefly Petunia are doing fundamentally different things.

One Makes Light. The Other Stores It.

The difference becomes obvious the morning after.

A phosphor-treated succulent must be charged again.

The particles inside absorb energy from an outside light source and release it slowly in the dark. Once the stored energy is gone, the glow fades until the plant is exposed to light again.

The Firefly Petunia doesn’t work that way.

Its glow comes from chemical reactions inside the living plant. It is bioluminescence rather than stored light.

That means no charging.

But don’t throw away the bedside lamp yet.

A softly glowing petunia is not designed to illuminate a room the way an electric bulb does. Its appeal is closer to watching a firefly than switching on a reading light.

Still, both approaches demonstrate something that would have sounded much stranger not long ago.

Living plants can become sources of visible light.

One method changes the plant’s biology, borrowing machinery from a glowing mushroom and connecting it to chemistry the plant already has.

The other leaves the plant’s basic light-making biology alone and adds material that can store and release energy from outside.

Both produce plants that glow.

But only one can truly claim the light as its own.

Put the Firefly Petunia in darkness, and it doesn’t need to remember the sunlight that came before.

It just keeps glowing.