I have a blue hydrangea that I planted last year that looks like it mostly died back. Did I do something wrong, and is there something I should do now to help it?

— Jennifer Duff, Waukegan

It is not unusual for bigleaf hydrangea (Hydrangea macrophylla) cultivars like your blue hydrangea to die back each year due to the winter cold. Simply cut back the dead stems to the point of new growth. Do not routinely prune them back hard in late winter or early spring as you might with ‘Annabelle’ hydrangeas. Give the plants extra time in spring to leaf out before determining whether or not the stems are dead. You should be able to determine what is dead and alive by now. Try to cut the plant back evenly so that you do not leave any stems that are dramatically taller than others.

You do not say exactly which blue hydrangea you planted — type will affect your results. An older variety of hydrangea, ‘Nikko Blue’, is at the edge of its hardiness zone in the Chicago area. This hydrangea blooms on large buds formed on growth from the previous season. After a harsh Chicago winter, a large number of…