Hydrangeas are woody shrubs with beautiful white, blue, pink, or purple blooms. Although these plants are hardy, special care should be taken to prepare hydrangeas for winter. No matter what climate you live in, you should offset the cold weather and loss of moisture by watering the soil and adding compost to it. In climates where winter temperatures do not dip below freezing, a layer of mulch will suffice to protect your flowers. If you live in a climate with winter temperatures below , you will have to build hydrangea shelters before the first frost of the season to protect your plants.