Sunday, March 13, 2011

A Reader's Question

“The hydrangeas on my terrace here in Northern Provence have started to bud, with some tiny pale green keaves already opening.  I am not pleased with the current shape of the bushes as each has lost many odd branches over the winter.  Is it still okay to prune them?  If so, do you have any tips?  Thank you!”
… Anonymous in Provence
           Oh to be anonymous in Provence… but that doesn’t answer your question.  First the conventional wisdom, and then the outliers.

The Conventional Wisdom:
If your hydrangea refuses to bloom, incorrect pruning is likely to be the culprit.  Hydrangeas should be pruned immediately after flowering, or in late winter well before spring (with one exception to follow).  Your plants will be sure to flower if you prune at the right time.  Hydrangeas bloom on new growth, so you can cut it to the ground if you chose, or merely tidy up.  

Even if you don’t get around to pruning at the right time, there are flower buds lurking along the length of the branch.  If you are forced to cut off the terminal bud that you know will bear the summer flowers, cut down to what you think will be the next flower bud and just wait a little longer.

I grow H. macrophlylla ‘Nikko Blue’ in Zone 5 in the Catskills, a climate much too cold for them.  I wrap them in burlap for the winter, but nonetheless the flower buds swell with moisture and then freeze in the early spring frosts that occur more often than not.  When it’s time to unwrap and prune, I cut back as minimally as possible, and hope for the best.  I have not been disappointed.

For you, dear Anonymous, a misshapen plant will bring you more unhappiness than one not blooming.  Shape it to whatever pleases you, and if the blooms don’t appear at the right time, buy an armload of cut hydrangeas at the enviable flower market in your enviable village and stand it next to your recalcitrant potted one.

Not knowing which of the many hydrangea varieties might be yours, here is a rundown of the basics: There are five major groups.  H. Arborescens and H. Paniculata bloom only from buds and new stems produced during the current growing season.  If you want to shape your plant or remove deadwood, cut the previous year’s stems to whatever height suits you or the plant’s location within your garden.  Or whatever height you think you need to support the weight of the blooms.

H. Macrophylla and H. Serrata form flower buds during late summer and fall, and the buds wait until the following summer to open -– unless they freeze.  If your conditions are optimal, don’t remove spent flower heads until the following late winter or early spring, removing only those stems that flowered the preceding summer.  To confuse matters further, the newer cultivars manage to bloom on both old and new growth, so no pruning is required.

The one exception to seasonal pruning is H. Quercifolia, the bold and slightly coarse Oak-leaf hydrangea, which blooms only on old wood.  It is most effectively used as a background plant in large areas, and fronted by rhododendrons, azaleas and spring ephemerals.

In summary, my advice to you is to do what you think best (remembering that plants don’t read the books), and please send pictures of Before, During and After.  

1 comment:

  1. Dear Sunday Gardener,
    You are an overflowing and bounteous fount of useful information. I don't know the type hydrangeas I have--I bought them years ago at the local Thursday morning marché. In the past, they have flowered yearly and early and have continued to bloom until fall in shades of blue, lavender and white. The plethora of new leaves pushing out of the pot soil seems to double in size & volume daily. I can only assume there are stalks soon to appear. The long stalks (some 18 inches or more) from last year have leaves that are very slow growing; so based on your advice, I shall take the plunge and prune them way down. I think we will all be happier! I promise photos, so let's hope they bloom! Merci beaucoup, chère madame! Anonymous in Provence.