One of the questions I am often asked this time of year is, “When can I prune my hydrangeas?” The answer is not as easy as you might think because the answer depends on the kind of hydrangea you have.
Hydrangea that blooms on last year’s wood: An example would be big leaf hydrangeas that have mophead blooms. These are probably the most common hydrangeas in the Pacific Northwest area. Remove any old dead flowers. Wait until you see the new green growth (leaf sets showing up end of February through mid-March here). Go 2 leaf sets below the old flower cluster and cut above the second set. If this hydrangea needs shaping or down-sizing, look at the whole plant. Leave about 1/3 of the branches as they are after dead-heading. Cut out the old dead branches – they will be obvious by now. And cut another third – especially those that are old and don’t have many active leaf sets – back to a major branch or all the way to the ground. Don’t take out too much without stepping back and looking at the overall shape. And don’t take out over 1/3 of the plant at this time. You can do more shaping next year if you wish.
Repeat bloomer hydrangea that blooms on this year’s wood: If this hydrangea is a repeat bloomer – blooming through the summer into fall – you can deadhead once the old flowers fade. Prune all branches to knee-level in mid to late February through mid-March if you want fewer but larger blooms – or just prune out the old dead wood as many of these have beautiful bark if left to grow without much pruning. An example would be Smooth leafed hydrangea (Hydrangea arborescens). Another hydrangea that blooms on this year’s wood is the Peegee hydrangea (Hydrangea paniculata).
If you have a climbing hydrangea, Hydrangea anomala petiolaris, prune it after it flowers as far as you can reach if it is getting out of control! This hydrangea can be quite vigorous once it starts to bloom – which may take a few years – but you would trim out the dead wood, deadhead, and if needed, cut back above a leaf set. Evergreen climbing hydrangeas (Hydrangea integrifolia & Hydrangea seemanii) seldom need pruning. Neither do Oakleaf hydrangeas (Hydrangea quercifolia) or the Mountain hydrangea (Hydrangea serrata) need much in the way of pruning.
Still have Questions? Contact Plant Amnesty at http://www.plantamnesty.org/ Next week: Fertilizing and caring for your hydrangeas through the year.