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Rhododendron information

Posted by GGardens 8 (My Page) on
Thu, Feb 21, 13 at 18:41

Does anyone have any info regarding rhododendrons -- varieties, best time to buy, transplant, etc.


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RE: Rhododendron information

  • Posted by bboy USDA 8 Sunset 5 WA (My Page) on
    Thu, Feb 21, 13 at 21:22

Buy in bloom during spring to get the flowers you want. Some kinds are in bloom now or about to bloom, for instance I have Rhododendron dauricum in bloom right now, saw 'Cilpinese' coming on at a local garden center recently. The parade at local outlets will probably continue into June, with the greatest number showing color April-May.

Apart from getting habit, foliage and flowers you want for a particular spot there are some cultural issues to be considered:

1. Foliage mildew. This came on in a big way in this area during the 1990s and can be quite a spoiler, the most susceptible kinds of rhododendrons even defoliating completely and dying - if not kept sprayed all spring. In general the most susceptible kinds are the most interesting ones with orange or yellow flowers, or other special features. While the old stereotypic tough "K Mart Rhododendrons" are the most resistant. But there are exceptions. A good way to get an idea of how the more common types are holding up is to look at local plantings, see which ones still look good and which are consistently shabby. Rhododendrons are still very common here yet most people do not spray them, you can pick up on some performance patterns pretty quickly just walking around neighborhoods with sidewalks and front gardens visible from streets.

2. Drainage. No wet areas for these, they don't like hot sun on the root zone either.

3. Summer watering. Lots of old specimens of tougher types around that don't get watered much, if at all, but in general expect to have to water in order to get decent results. Especially with newer plantings they may even wilt and die if you don't pour it on during dry weather.

4. Mulching. Like other trees and shrubs establishment and growth much enhanced by covering the soil around them with organic material (arborist wood chips are the best) or rocks - anything that shades the root zone and retards frost penetration.


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RE: Rhododendron information

I'm something of a native plant snob, but still can't resist some of the really nice Asian varieties. I purchased a 'Clipinese' last year. It budded back in December and appears to be in a holding pattern right now.

Ditto the above pieces of advice. In addition, use good bark mulch (fir, pine, redwood, oak, etc.). No manure or lawn clippings. Rock mulch is OK, but is better for desert plants.

I'm amazed at how tough established rhodies can be. I have a mature (70+ year old) Black walnut in my front yard. There are two 7' rhodies 10-15' from the trunk (planted by a previous owner), yet they survive the the juglone that is emitted from the walnut's roots and leaf litter. They don't look good, but they flower every spring and exhibit a little growth afterwards.


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RE: Rhododendron information

  • Posted by bboy USDA 8 Sunset 5 WA (My Page) on
    Fri, Feb 22, 13 at 17:55

The not looking good could be foliage mildew, this is by now pretty much universal up here. Afflicted plants have a sometimes quite visible dusty coating of fungus on the leaf undersides, with dark spotting and pale blotching carrying over onto the upper sides. Leaves die and drop prematurely, resulting in a more gaunt aspect than normal. Leaf size may diminish over time, if severe enough infestation may diminish entire plant over time - some kinds go bare and die in only a few years. At the other end of the spectrum are those that chug along almost as though not infested. These are the ones to watch out for, if you don't want to spray - or put up with the results of not spraying less tolerant kinds.


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RE: Rhododendron information

  • Posted by saly Z7, NW, USA (My Page) on
    Sun, Mar 3, 13 at 22:16

my rhododendrons are planted int he south west, west directions. They have less foliage and flower very scanty in early spring...I dont see any powdery mildew or any problem in leaves shape.
What do i do to get it going good this season?

Thx,
-Saly


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RE: Rhododendron information

  • Posted by bboy USDA 8 Sunset 5 WA (My Page) on
    Mon, Mar 4, 13 at 16:59

Depends on what the problem is. Might they be burning up in the summer? Exposure is wrong unless site has shadows over it during hot weather.


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RE: Rhododendron information

  • Posted by saly Z7, NW, USA (My Page) on
    Mon, Mar 4, 13 at 21:56

Is this a good time to transplant them....they are 6-7 yrs old now and woody...
Thx,
-Saly


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RE: Rhododendron information

I am giving up on R. 'Cilipinens' I'm in a weird little cold sink in north Seattle. Every year since I moved here (five years ago), it has suffered winter damage. This year it didn't, but last night all the open flowers got frosted. Free to a good home as soon as I figure out what I'm going to replace it with.


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RE: Rhododendron information

  • Posted by bboy USDA 8 Sunset 5 WA (My Page) on
    Mon, Mar 4, 13 at 23:33

Saw some frost damage to this today in Bellevue as well.


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RE: Rhododendron information

I'm thinking Korean Abelia Leaf.


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RE: Rhododendron information

  • Posted by bboy USDA 8 Sunset 5 WA (My Page) on
    Tue, Mar 5, 13 at 10:26

Some years that has a twig dieback. Growth is also slow. Needs a hot location, one in the parking lot plantings at Molbak's has done well, is pretty showy this year. There are also one or two at the Greenlake PCC, again in a parking lot where there is asphalt around.

The typical white plant leaves me a little cold, I'm thinking if the bigger one at Molbak's was one of the pink forms (Roseum Group in British publications) it would be more compelling.


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RE: Rhododendron information

Korean summers were pretty hot I remember. I've never seen the 'Roseum' except in photos. I may have to rethink that.


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RE: Rhododendron information

  • Posted by bboy USDA 8 Sunset 5 WA (My Page) on
    Tue, Mar 5, 13 at 15:11

Pink cultivars offered by Heronswood and Greer Gardens in the past, have also seen one at Wells-Medina nursery, Bellevue - do not know if any of them have it this year.


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RE: Rhododendron information

  • Posted by botann z8 SEof Seattle (My Page) on
    Wed, Mar 6, 13 at 13:34

I have a Rhododendron called 'Olive' blooming now. I pruned it for an open look, given it's location.


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RE: Rhododendron information

That's lovely, Botann.


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RE: Rhododendron information

  • Posted by corrine1 7b Pacific Northwest (My Page) on
    Thu, Mar 7, 13 at 12:58

Amazing work on that pink rhody, Mike! You made me smile.

Corrine


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RE: Rhododendron information

  • Posted by botann z8 SEof Seattle (My Page) on
    Thu, Mar 7, 13 at 13:21

Glad you like it.
I'm not afraid to cut branches with blossoms. Some people treat blossoms as a commercial food crop and don't do anything to lose them. I'm after form over quantity most of the time. Trouble is, I have more rhododendrons and other plants to prune to keep up.
I will post more pics as they bloom.
Mike


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RE: Rhododendron information

I'll admit I prefer to prune after bloom. Do you at least pot the flowering branches in a vase?


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RE: Rhododendron information

  • Posted by botann z8 SEof Seattle (My Page) on
    Thu, Mar 7, 13 at 13:53

I pruned these branches before it bloomed. Crazy as it sounds, I prune Rhododendrons at all times of the year. I cut the offending branch at the beginning rather than out on the tip where I would get a lot of secondary growth subject to damage by frost at certain times of the year like late summer or early fall pruning.
Yes, I bring in blossoms for Marilyn to put on the dinner table when they're available. :-) Sometimes just a trusses in a bowl of water. Hey, it works for me!
Mike


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