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Avatar for sydwest
May 29, 2020 2:50 AM CST
Thread OP
Sydney, Australia
I have a birds nest fern growing on volcanic rock on kitchen window sill. A white growth has recently flourished and I'm guessing this might be a fungus. Any suggestions on how to treat to get rid of it will be appreciated.

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Avatar for oneeyeluke
May 29, 2020 11:42 AM CST
Name: one-eye-luke US.Vet.
Texas (Zone 8a)
Quitter's never Win
Birds Cat Lover Dog Lover Hummingbirder Organic Gardener
Efflorescence is a white, chalky substance that appears on the surface of natural stone, clay brick, concrete pavers or any other porous stone material.This moisture is drawn to the surface of the stone where it evaporates, leaving the salts behind as a white haze. Sometimes it can be very hard to remove and you will need a strong acidic liquid. Try water and with a toothbrush first and if that doesn't work then go to the next step.
Add undiluted vinegar and apply it to your stone with the plastic toothbrush. Make sure you don't get any on your plants. See if it removes the white residue. You may have to use a mix of deluded muriatic acid mixed with water.
NOT A EXPERT! Just a grow worm! I never met a plant I didn’t love.✌
May 29, 2020 11:56 AM CST
Name: Daisy I
Reno, Nv (Zone 6b)
Not all who wander are lost
Garden Sages Plant Identifier

I agree, it could be leaching of minerals from the lava rock but, I would not use any of Luke's cures if I wanted to keep my plant alive.

The other possibility is a mold - you could try spraying it with a fungicide. Otherwise, a toothbrush and some scrubbing is all I would recommend. Personally, after I determined it was mineral leaching and not mold, I would let nature take its course.
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and proclaiming...."WOW What a Ride!!" -Mark Frost

President: Orchid Society of Northern Nevada
May 29, 2020 1:39 PM CST
Name: Gina
Florida (Zone 9a)
Tropical plant collector 40 years
Aroids Region: Florida Greenhouse Tropicals
I like that mount. I have used crushed lava rock to pot up lithophytes before but never thought of using a block as a mount. These large pieces of lava rock used to be popular with Anthuriums mounted on them (the Andreanum types)
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May 29, 2020 3:18 PM CST
Name: sumire
Reno, Nevada (Zone 6a)
The white is minerals leached out of the rock. Unsightly but not harmful. Water and a toothbrush might take some off, and watering by dumping the whole plant in a bucket for a moment might (it depends on the rock) keep it from growing more.

Don't use vinegar (or any other acid) next to your fern. You'll kill it.
Avatar for sydwest
May 29, 2020 7:50 PM CST
Thread OP
Sydney, Australia
Thanks for all the helpful observations and suggestions.

I've cleaned it gently with a toothbrush and water and it's now looking good again. Thank You!

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