By the way of  contrast,  rhododendrons belong to a category called ‘Stress-tolerators’,  (J.P. Grime, Plant Strategies and Vegetation Processes, Wiley, 1979).   Stress-tolerators are those slow-growing,  long-lived plants whose first priority is to put all their energy into building up a substantial structure of roots, shoots and leaves.  They frequently delay flowering until they are  many  years old (from seed that is).

     Stress-tolerators also differ from Ruderals in that the percentage of their energy from photosynthesis going into seed production is very small.  You might contrast a rhododendron seed, which is tiny, with that of wheat, which is maybe a thousand times heavier. 

     By now you should be able to see where I am going.  The “energy drain” justification for deadheading rhododendrons doesn’t have a leg to stand on.  It seems likely that most or all of the photosynthesis required to nourish the growing seeds goes on in the walls of the seed capsules.  The seeds do not inhibit shoot growth by “sucking up” the available energy supply.  In rhododendrons the seed is not a “parasite” on the plant.

 

To Deadhead or not to Deadhead? 

     Don’t misunderstand the above.  I’m not saying that deadheading is pointless.  What I’m saying is that the justification many of us have used for deadheading may be wrong. 

     When you compare new shoots sprouting just below a flower truss with those coming from vegetative shoots on the same plant, the shoots below the flowers will usually be shorter or start growth later.  What developing seeds do, apart from absorbing a microscopic amount of foodstuffs, is produce hormones that then diffuse down the stem.  I suspect this is a hormonal effect that slows shoot growth. 

     At a certain time in the growing season a shoot has to decide whether or not to initiate a flower bud for next year.  This decision time is quite early, I don’t know when, but probably June or July.  It is long before the tip swells to indicate a flower bud.  If a shoot is small or delayed in its growth it will decide to not flower next year. 

     So the reason for deadheading becomes one of trying to promote shoot growth.  You can do this by deadheading immediately after the petals shrivel.  I doubt if deadheading later in the summer or fall will do anything to increase the abundance of flowers. 

     You will have realized that gardeners were deadheading long before pseudoscientific reasons for it were made up.  Even gardeners in Victorian times did it.  So what was their reason?   Well, labor was cheap and the bushes looked neater, and I think that is why most of us do it.

____________________________________________________________

 

The Pilchuck Fuchsia Society will be joining us this month for the gift exchange so be on your best behavior; we don’t want to embarrass Shirley.  Unfortunately your President will be in sunny San Diego the week of the meeting so Ellen Moon will be leading the fun.

Pilchuck Pollinator