Tiny White Things on Spinach Leaves = Calcium Oxalate Crystals?

Bugs on spinach or something else?

See the white dots in the middle?

I was checking up on my spinach plants recently and noticed that one of them had a bunch of tiny white dots on the leaves, especially the newly emerging ones in the center. Hmm...I thought it might be due to some kind of pest, since the plants were outside. The more I look at the plant though, I thought it had to be something else, because the leaves appeared perfectly healthy, no bites taken out, no sign of distress. So I Googled and Googled some more...until I found someone on GardenWeb saying they were not bugs, but calcium oxalate crystals.

This was an interesting possibility that I hadn't thought of. I then researched calcium oxalate and found out:

1. It is a major component in formation of human kidney stones.

AND

2. Plants can indeed accumulate it within their leaves.

So with that possibility in mind, I forged ahead in my Googling to find this very relevant post on spinach from Helping Gardeners Grow. In her post there, Pam also notes the tiny white specks on her homegrown spinach leaves. Many plants contain oxalates in their leaves. However, spinach has more oxalates than your average vegetable, which combine with calcium to form crystals when exuded from the plant's leaves.

What a relief! So I have nothing to worry about after all. No bugs, just normal calcium oxalate crystals.

A closer look at the calcium oxalate crystals. They're mostly on the inner, more crinkled leaves.