Rhododendron Troubles

Discussion in 'Ericaceae (rhododendrons, arbutus, etc.)' started by BradH, Jun 11, 2020.

  1. BradH

    BradH New Member

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    Hello friends.

    I’m having trouble with four of our six rhododendrons and I’m on the hunt for answers.

    At the moment two are dropping leaves, one is drying out, and the other has new growth but has a powdery mildew all over. All were planted this spring, and flowered beautifully.

    It’s been quite wet, so I assumed perhaps it was from all of the rain. However, I’m now starting to suspect that there is more going on.

    I’ve attached a couple of photos, and hope that someone will have some advice or recommendations for me. If you know a gardener or master gardener who would be willing to have a look, please send them my way!

    Thanks in advance for the help!
     

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  2. Margot

    Margot Generous Contributor

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    On the whole, I would say your rhodos look pretty good especially considering they were planted just this spring! The cool, damp weather so far this year has been perfect for new plants to establish their roots. The fuzz you see on the tops of the leaves is called 'tomentum' and is considered to be an attractive feature of rhodos. Fuzz underneath the leaves is called 'indumentum', also quite lovely on many plants. The colour can be whitish or brownish; depends on the species or cultivar.

    I wouldn't worry about the yellow spots on a few of the older leaves. It could be the plants were a bit stressed by being moved from pots to garden or it could be they are about to drop off as 2- or 3-year-old leaves often do. Over a few years, you'll get to know what is normal for your rhodos.

    I hope you have the names for the plants because you can learn a lot about their specific needs if you do. A very good place to find excellent information and advice about growing rhodos is on the American Rhododendron Society website: The American Rhododendron Society Welcomes You

    Be sure not to let rhododendrons ever dry out, especially when they are settling in as yours are. Oft repeated advice is to mulch them well with wood chips, shredded leaves or coarse composted bark mulch, all over the root zone but away from the trunk.
    http://osu-wams-blogs-uploads.s3.am...-Study-Group-Mulch-Paper-04-23-2018-Final.pdf

    One last comment: I took the Master Gardener course about 25 years ago and learned a lot, especially about how to find answers to gardening questions. I can tell you without hesitation though that there are many people on these Forums who know as much or more than most MGs.
     
    Last edited: Jun 11, 2020
  3. BradH

    BradH New Member

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    Thank you, Margot, for your reply! I’m relieved to hear that you think they’re looking good.

    Even with so many leaves dropping that i have bare branches, that still seems normal?

    I do know that these plants are Crete and Hotei. My Catawbiense Boursault are perfectly happy and healthy, but they were larger (older) plants that I purchased.



     

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  4. Margot

    Margot Generous Contributor

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    I would keep a special eye on this one because it seems to have only last year's leaves left. New ones are starting to appear though so that's good. If you could bring yourself to do it, it might be a good idea to remove the current flower buds so that the plant can throw all its resources into establishing roots and producing leaves this year. If you mulch it and keep it watered over the next few months, it should start looking happier. Don't fertilize.

    Also, read up on what that specific rhodo likes in terms of sun/partial sun to make sure you have it in the right location.
     

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  5. BradH

    BradH New Member

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    I have just dug up the two Hotei. These two are in the worst shape. They were field grown in Langley, but seem now to have a large mass of clayish soil around the root ball. There are no roots growing through, whatsoever. I took some of the clay from the ball, and from around the stem. I’ve added gravel to the beds, and into the holes where I’ve replanted them slightly higher than before
     

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  6. Margot

    Margot Generous Contributor

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    I hope someone else weighs in on your rhododendron challenges because I have never encountered one grown in clay before. Rhodos should not be grown in clay but, now you own a couple that were, it's hard to know what to do next. I've never done this myself, but I'd be tempted to soak the root ball in a container of water for a few hours - no longer - and see if you couldn't wash off some of the clay without damaging the roots. Putting gravel in the planting holes or beds is not a benefit. Rhodos thrive in soil with lots of humous so planting them higher than before as you have done is good, with plenty of humous around them and topped with a few inches of mulch is about the best you can do at this point. It will be a big challenge to keep them adequately watered during the dry months - you can't let that clay ball dry out.

    Hotei is a lovely cultivar. If you haven't read this site, it gives a good overview - Rhododendron 'Hotei' | Landscape Plants | Oregon State University I really hope you will be successful nurturing your rhodos past these early difficulties and enjoy their beauty for many years to come.
     
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  7. BradH

    BradH New Member

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    Thank you for all of your help and input, Margot!

     
  8. Ron B

    Ron B Paragon of Plants 10 Years

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    Thousands and thousands of field grown rhododendrons have been produced in sticky soils for many years. Remove the gravel and any other textural or drainage alterations you have installed and replant your shrubs in the existing soil, without modification. As long as they will not be sitting in mud or having their root zones baked by full hot summer sun exposure the soil they came in shows what falls within the range of suitability. The defoliation and discoloration may trace back to adversities the plants were subjected to prior to purchase.
     
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  9. BradH

    BradH New Member

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    Thanks for the input, Ron. Any need to try and loosen those root balls? I read here, Planting Rhododendrons and Azaleas, that I should. It also says to cut some of the roots, but I’m unable to see any roots for the sticky soil.

     
  10. Margot

    Margot Generous Contributor

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    I'm interested in knowing where that is happening - and why? I've bought about 200 rhodos over the past 50 years here in BC and have never had to deal with a single one grown in clay or even 'sticky' soil.

    I think your advice to plant in the existing soil is better than mine to surround with humousy soil because it should make watering easier unless the existing soil is very sandy.
     
  11. Ron B

    Ron B Paragon of Plants 10 Years

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    Whatever current field grown rhododendron production levels are there now try the Willamette Valley for starters. An area where I have viewed a rhododendron field that was so big I could not see the end of it. Fine textured, adhesive soils are favored for field growth of nursery stock of all kinds because the balls hold together after the plants are dug.

    Heath family plants such as rhododendron have very dense, brittle root systems that do not lend themselves to being worked on at time of planting.
     
  12. Margot

    Margot Generous Contributor

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    This sounds more like a benefit to large-scale producers than to purchasers such as BradH or to the plants themselves when moved into real-life situations.
    I wouldn't be surprised if they exist mainly to supply Costco. Also, how many are still alive and thriving 5 years after purchase.

    What do you think smaller-scale, specialty producers in Washington State and BC would think of the practice?

    It would be interesting to know how prevalent that kind of production is here in BC eg." a rhododendron field that was so big I could not see the end of it.." More and more, local ARS clubs are propagating special species and cultivars . . . join one and learn!
     
    Last edited: Jun 13, 2020
  13. Margot

    Margot Generous Contributor

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    Re-reading my last comments, I realize that they seem to be directed at Ron B when I was actually just thinking 'out loud' about how growers produce the plants.

    I apologize if my remarks came across as critical toward Ron whose expertise and involvement on these Forums is unparalleled and much appreciated.
     

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