White Rectangular Shaped "Eggs" on The Back of Lea

[Brandywinegirl]

Every year there are these white, chalk-like rectangular things on the back of many of my Hydrangea leaves. I don't see them on anything else in my garden. Does anyone have an idea what this is? Is it insect eggs?
Thanks for your help!

[applestar]

If insect eggs, I would think the leaves would be eaten -- are they?

I'm thinking spider nest silk stretched over the puckered back of hydrangea leaves. But you said chalk-like? Do they come off like powder?

[Brandywinegirl]

No applestar, the leaves are not eaten. It's not spider nest silk, Its dry. I'll check & see if it comes off like powder if I can find any leaves with this on it.
Thanks for helping me problem solve.