How to protect plants from late frost in spring.

When you know there's going to be a frost at night, Yes, cover them. I use fleece blankets as rhey are light weight or go to a thrift store and get mattress covers or used fleece blankets. They will not hurt the bush. Some people use sheets as they are light weight, but I don't think that sheets trap the needed warmth.

http://homeguides.sfgate.com/protect-hydrangeas-late-frost-66049.html

If these are rather large bushes, you can also invest in garden blankets. They are lightweight. There are even "pup tents" that are fairly inexpensive. Good Luck.

Hello, you could take plastic tarps or plastic and put over them and then either stake them down or anchor them down with large rocks. The light weight plastic shouldn't hurt the branches.

You can use stakes in the ground near the edges of the hydrangea and drape heavier blankets over the plants like a tent. Or if they are near a fence, use that to keep the blankets from harming the plants.

Cardboard boxes can also be used as well as plastic tubs, rose bush cones and the like. Use a rock or brick to add some weight to these kinds of covers if you fear they'll go flying.

We don't cover our hydrangeas. According to this article you should cover the base with some kind of mulch, but that's it:

http://www.diynetwork.com/made-and-remade/learn-it/winter-care-tips-for-hydrangeas

I agree with the above comments. You should cover your plants when expecting a frost. I have lost many plants (mostly veggies) to frosts. You could really use just about anything to cover them. Blankets, sheets, cardboard and even newspaper can be used. Good luck.

Put lights on them and cover.