Preparing Bigleaf Hydrangeas for Winter

I woke up to 37 degrees F this morning, a stark reminder that I need to prepare to wrap some of my bigleaf hydrangeas (macrophyllas) for winter. Those that aren't planted in protected locations as I described in my earlier blog posts, https://bit.ly/2lRGNlm and https://bit.ly/2A8tzZE need a little help if I want to give them their best chance of having their buds make it through the coming winter to see flowers in 2019. Exactly what does this mean right now? SHRUBCOVERS : something I can use to safely protect the plants from ice and snow, maybe even give them a few degrees of insulation.