Rhododendrons: Rhodo (PJM) problem

Discussion in 'Ericaceae (rhododendrons, arbutus, etc.)' started by Louis Peterson, Apr 3, 2006.

  1. Louis Peterson

    Louis Peterson Member

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    Lions Bay, British Columbia
    A gardener asked me about her problem: She planted seven PGM rhodos over two years ago, in a row as a screen. All bloomed well last year. This year, six have bloomed well, but the seventh, at the end of the row, has not bloomed. It has retained the brown winter colour of its leaves, and it set buds, but has not developed further.

    Could the problem be root weevils, or a root fungus, or ??? How to diagnose? Could the problem (disease?) spread to the other PJMs? How to cure?

    Thank you, Louis Peterson.
     
  2. Ron B

    Ron B Paragon of Plants 10 Years

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    Phytophthora root rot is likely. Rhododendrons and azaleas apt to fail on less than highly aerated soil, typical substrates in the wild are sand, gravel or moss. I have seen many plantings of 'P.J.M.' in particular dwindle away in parking strips and similar settings. A curious thing with less tended local plantings of rhododendrons and azaleas in general is that often part or most of the specimens in a grouping will gradually discolor and die out, as though the site is unsuitable--but few to several will persist and go on to make satisfactory specimens. I have also seen the same pattern with Quercus ilex here.
     
  3. chowntown

    chowntown Active Member

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    Root weevils are highly unlikely wth PJM rhodos as they are one of best varieties in terms of resistance to root weevils. It sounds like phytophthora root rot - remember rhodos like to have lots of air around their roots and are very sensitive to water constantly around their roots. Amend with lots of good organic matter (sphagnum moss is best) and adding some sand probably wouldn't hurt either
     
  4. Ron B

    Ron B Paragon of Plants 10 Years

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    Do not incorporate organic amendments or sand unless entire potential rooting area for many years is worked over. It is undesirable to leave plant sitting in pocket of amended soil surrounded by larger area of unamended soil. Do not use sand at all unless enough is used so that more than half of finished soil (sand already in soil plus added sand) consists of sand. Replanting in new layer of coarser soil placed on top of existing soil easier and more direct than amending existing soil.
     

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