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Re: selecting and growing azaleas

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  • S. M. Henning
    ... Hi James, This is a fantastic document and represents a lot of very worthwhile effort. I did find one problem. It states under Site Selection that:
    Message 1 of 2 , Nov 5, 2007
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      James Thornton wrote:
      >
      > it's here and on line! the uga extentsion ofc publication"selecting
      > and growing azaleas".this is a booklet by the uga in cooperation with
      > the oconee chapter of the azalea society of america.
      > take a look:
      ><http://pubs.caes.uga.edu/caespubs/pubcd/B670/B670.htm>http://pubs.caes.uga.edu/caespubs/pubcd/B670/B670.htm
      >
      ><<http://pubs.caes.uga.edu/caespubs/pubcd/B670/B670.htm>http://pubs.caes.uga.edu/caespubs/pubcd/B670/B670.htm>

      Hi James,

      This is a fantastic document and represents a lot of very worthwhile effort.

      I did find one problem. It states under "Site Selection" that:

      "Materials commonly used to lower soil pH are wettable sulphur,
      ferrous sulfate and aluminum sulfate."

      While this is true, it is also true that repeated application of
      aluminum sulfate is toxic to azaleas and hence it should not be
      recommend. In fact, a note should be posted to warn against using
      it. Unfortunately many people also are unaware of the problem.
      Aluminum sulfate is great for hydrangeas but can kill many other
      plants. Here are some references:

      Mass. ARS Chapter by Joe B.Parks
      [http://www.rosebay.org/chapterweb/jpchange.htm%5d:
      "Never use aluminum sulfate to increase soil acidity as it is toxic
      to many plants including rhododendrons. This is a most important
      point! Under no circumstances should you use aluminum sulfate
      (Al2SO4) around your rhododendrons. As was pointed out in a previous
      article, soluble aluminum is toxic to rhododendrons. The chemical,
      aluminum sulfate, is soluble in water thus the aluminum component is
      immediately available - and toxic - to the plants. As the pH level of
      the soil decreases, the aluminum component becomes increasingly
      soluble - and thus increasingly toxic. Therefore, although aluminum
      sulfate will certainly reduce the soil acidity, it can, and will,
      quickly injure and may even kill your rhododendrons. Even though the
      plants may tolerate small quantities of this material, why should any
      quantity of a toxic material be added to the soil when other
      perfectly safe materials such as sulfur are available?

      I once saw an entire bed of rhododendrons (no, not mine) killed
      within a week by a "proper" application of aluminum sulfate. Even
      small amounts of aluminum sulfate can stunt rhododendron (and azalea)
      roots and reduce their ability to absorb nutrients and water. True,
      organic materials in the soil will buffer aluminum and reduce its
      toxic effects, but the toxic effects occur immediately and the
      buffering effect is slow. Too, how do you know there is sufficient
      organic material available. Why take a chance with your valuable
      plants, do not use aluminum sulfate regardless of what anyone tells
      you!"

      Hank Schannen of Rare Find Nursery
      [http://www.rarefindnursery.com/index.cfm/action/howtoplant.htm%5d:
      "Do not use aluminum sulfate to acidify the soil because aluminum can
      be harmful to the plants over time."

      H. Edward Reiley in Success with Rhododendrons and Azaleas:
      "Plants in the genus Rhododendron are rather tolerant of aluminum,
      but can be damaged by excess aluminum in the soil. Aluminum sulfate
      should therefore be used sparingly, if at all. As soil pH drops
      below 5.0, more aluminum ions become available in increasing numbers."

      American Rhododendron Society [http://www.rhododendron.org/planting.htm%5d;
      "Do not use aluminum sulfate to acidify the soil because aluminum is
      harmful to the plants."

      "Azaleas as Bonsai" by Jim Robinson (6/2/93) Rocky Mountain Bonsai
      Society [http://www.rockymtnbonsai.org/html/azaleas.html%5d
      "Avoid aluminum sulfate or other aluminum compounds as aluminum is
      too toxic to azaleas. "

      Colorado Extension Service
      [http://www.ext.colostate.edu/mg/files/gardennotes/222-SoilpH.html%5d:
      "Aluminum sulfate will also lower pH, but it is not recommended as a
      soil acidifying amendment because of the potential for aluminum
      toxicity to plant roots."

      Ohio State University [http://ohioline.osu.edu/hyg-fact/1000/1078.html%5d:
      "DO NOT use aluminum sulfate to acidify the soil, as the aluminum
      residue may be harmful to the plants."

      University of Florida [http://hort.ifas.ufl.edu/gt/iron/iron.html%5d:
      "Aluminum sulfate can be applied at the rate of one-fourth pound per
      square yard of bed area. Do not apply aluminum sulfate more often
      than one time in a 12-month period. Repeated use of aluminum sulfate
      can lead to a toxic condition."

      University of Minnesota
      [http://www.extension.umn.edu/info-u/plants/BG497.html%5d:
      "Although aluminum sulfate is available in garden centers and also
      lowers pH, it can be toxic to roots. There are better choices."

      Organic Gardening Tips
      [http://www.organicgardentips.com/how_to_grow_azaleas.html%5d:
      "Because of the acid soil required, aluminum sulfate has probably
      spelled the doom of more azaleas plants than any other single thing."
      --
      Cheers, Steve Henning in Reading, PA USA Zone 6

      Visit my Rhododendron and Azalea web pages at:
      http://rhodyman.net/rasite.html

      Also visit the Rhododendron and Azalea Bookstore at:
      http://rhodyman.net/rabooks.html
    • S. M. Henning
      ... Actually the UGa Cooperative Extension Service is the part of the Colleges of Agricultural & Environmental Sciences and Family & Consumer Sciences that
      Message 2 of 2 , Nov 5, 2007
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        Bob Kelly wrote:

        >That would the University of Georgia (UGA)-- the Cooperative
        >Extension Service. In other words, their Ag school.

        Actually the UGa Cooperative Extension Service is the part of the
        Colleges of Agricultural & Environmental Sciences and Family &
        Consumer Sciences that includes: county agents, home & garden
        publications, supports the 4-H program, and answers questions about
        agriculture, environment, youth, families, and consumer topics.
        Their students are all the citizens of Georgia, not just the college
        students. They do agriculture and consumer research and public
        education.

        Land-Grant Universities were established under the Morrill Acts of
        1862 and 1890. The mission of the land-grant universities was
        subsequently expanded by the Smith-Lever Act of 1914 to include
        cooperative extension - the sending of agents into rural areas to
        help bring the results of agricultural research to the end users.

        The Cooperative Extension Service, also known as the Extension
        Service of the USDA, is a non-formal educational program implemented
        in the United States designed to help people use research-based
        knowledge to improve their lives. The service is provided by the
        state's designated land-grant universities. In most states the
        educational offerings are in the areas of agriculture and food, home
        and family, the environment, community economic development, and
        youth and 4-H.
        --
        Cheers, Steve Henning, Valley Forge Chapter, ARS; PA, USA Zone 6

        http://rhodyman.net/rasite.html

        http://rhodyman.net/VFARSHistory.html
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