Prolonging the life of cut hydrangeas

I was thrilled with my Thanksgiving centerpiece, but, within a day or two of my making it, the hydrangea (back right) abruptly wilted, leaving an unfillable gap.  Why would a fresh-cut hydrangea die so fast?  I have since learned that hydrangea blooms are notorious for their delicacy.  To make them last longer and more reliably, florists have developed a trick or two.  I haven’t tried them yet, but I’m going to.

Hydrangeas draw in water slowly because of their woody stems, so the key is to make it easier for the cut stem to draw.  Florists achieve this in several ways.

One technique involves stripping away the outer bark at the bottom end of the stem, just as you might peel away the tough outer skin on a stem of broccoli before cooking.  Use a sharp knife to scrape off the tough outer layer of hydrangea bark.  Some florists cut a single gash that exposes the white flesh of the stem; others neatly scrape off a uniform amount all around, leaving a thin layer of bark covering the last inch or two.

Cut a cross into the bottom of the stem’s cut end.  And be sure that each stem is cut at an angle so that the end is not “plugged” when resting in the floral container or vase.

A second technique for preserving the bloom involves dipping the cut end of the stem in alum (a white powdery substance bakers sometimes use).  A professional florist I spoke with said that this was the single most reliable and efficient way to prolong the bloom.

I’ve read that briefly plunging the cut end of the stem in hot water before placing it in the vase is effective, too.  This is a technique that Martha Stewart employs.  She recommends plunging the ends of the stems in boiling water for 30 seconds.  This technique requires some caution, because one must protect the heads of the flowers from the effects of the heat.  (Some people recommend wrapping them in paper or damp paper towels.)  Though it sounds off-beat, this is a traditional floral method, commonly used when arranging other woody-stemmed plants, like forsythia.

If you happen to have experience using any of these techniques, I’d love to know.  Do they really work?  Next time I buy hydrangeas for the house, I’m going to try the alum approach.