Hello. I have done a bit of searching through the forums in hopes to find an answer to my problem, but haven't had any luck so I thought I'd reach out in hopes you guys might have some insight on a recent, unusual findings on my 4 pilea peperomioide plants. I've had them since Oct 2015 and they've all been doing really well. However, I recently noticed something very unusual on the underside of most of the leaves. A very symmetrical pattern of white crystal-like, "grains" or "balls" around the perimeter and into the center on the underside of the leaves. The best way I can think to describe them is similar to table salt in size and texture, but a little more opaque than salt. If you gently rub your finger across them, they pop out of the leaf, leaving a small crater (see images).

Quick Plant Care History:
SOIL:
I bought them from an eBay seller and upon receiving them, I planted each one in a slightly different potting soil (LGM, EB Stone, another organic brand, etc.) and if they didn't already have perlite pre-mixed, I added a little to aid in drainage.
LIGHT:
2 of them hang in a north-facing window and the other 2 sit in a south-facing window.
WATER:
I water them when the soil is almost completely dry, so every week to week & 1/2.
FOOD:
I've only fed them once with Earth Juice GROW and at low-strength. It may be worth noting that I fed them 2 weeks ago, which was ~a month AFTER noticing these strange little grainy-patterns on the leaves, so it's not a direct result of the food.

I don't THINK it's insect-related, and the plants still appear healthy & happy. I just don't want to find them suddenly struggling and realize I'm behind the 8-ball to revive them. Any guidance or suggestions you guys may have is greatly appreciated. I've also included photos.

Thank you,
Emily

That really does look like salt, doesn't it? I have no idea what it is, but hope someone who does will respond just in case I need to know in the future. Your first photo looks like some I just saw when I googled this plant - those little spots on the tops of the leaves but they don't make a point of showing the undersides of the leaves. Its a mystery - good luck finding out the solution, Emily.

Thanks, Carol. After I posted, I found a photo online of a p.pep. that does have the same pattern, but I don't see any discussion about it. Once you click the link & the page opens, you may have to click "Fit to Window" on the top left: http://www.plantsystematics.or...

What doesn't kill us makes us stronger. The same must be true of plants. Here's another one to live by: "You never really know a plant until you've killed it." Let's hope the first saying applies in this case.

Dear EmilyD2,

I would like to kindly ask you how did you solved the problem with the white spots? I got one plant just one week ago and suddenly I see the same. I hope it survives. It is so difficult to get it in our country.

Thanking you in advance for your info, Olive

Dear Emily,

how is your pilea? I find the same white grain on my pilea and I do not what to do and I don't want to lose it.

Thanking you in advance for your info. Olive

Hi Olive,

I honestly believe it is simply part of the plant. All of mine are still doing very well (image attached). I keep them inside, in bright but indirect light and they're thriving! I'm also cautious to not over-water them.

Hope this helps.

Emily

Could this possibly be spores for reproduction? They remind me of the back of a fern. Mine has it also and is very healthy and has several new small plants.

Those are sap secretions from the leaves. They are indicative of a healthy plant, not of a problem.

Tamara - Only Ferns have spores so that they can reproduce. Other plant species reproduce through flowers.

The white spots on the pilea leaves can be attributed to Oedema. This condition is not fatal, nor is it caused by insects. It is typically related to light and water. Essentially the leaves cannot transpire moisture fast enough, the cause maybe due to overwatering, high humidity, or not enough light. Google Oedema for tips on how to reduce it.