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 Rhododendron rex 
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Joined: Sat Jul 09, 2016 9:16 pm
Posts: 46
Location: Klaipeda Lithuania 6B zone 55°42 N
Post Re: Rhododendron rex
Thank you David for the reply, but what about the rhododendrons, especially large leaved ones? What is their hardiness pattern - could they better take a short spell of -20C or four weeks of -15C, given they are somehow protected from extra stress of sun and wind?


Fri Feb 03, 2017 8:46 am
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Joined: Mon May 30, 2016 3:16 am
Posts: 186
Location: Missouri USA
Post Rhododendron rex
Here is a link from the Morton Arboretum - looks like rapid and extensive temperature variations are more damaging.
http://www.mortonarb.org/trees-plants/t ... and-shrubs

Excerpt from the above link - "In general, low temperatures are much less damaging than rapid and extensive variations in temperature."


Fri Feb 03, 2017 10:47 am
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Joined: Tue Jun 14, 2011 12:01 pm
Posts: 327
Location: Maryland, USA
Post Re: Rhododendron rex
From having tried a lot of borderline hardy and subtropical plants over the years - and folding in reports here of rexes surviving for years in Nova Scotia - I'm going to go out on a limb to say a properly dormant Rhododendron is a pretty hardy thing. The "four weeks of -15C" sounds a lot like what made our recent 'polar vortex' winters so bad. It wasn't just that they got cold, it was how long and sustained it was. What I saw was that meso-climate plants like Eucalyptus parvula, Viburnum tinus, Escallonia etc...stuff from places - in a broadly geographic sense - with mild winters...took an especial beating from the sustained cold. They might not have cared about a brief dip to -17C, but each time the temperature plunged down, they looked more and more battered. Likewise the Trachycarpus I'd had the very bad luck to plant just before the first polar winter. Each excursion from the norms produced more and more damage.

OTOH even my supposedly borderline rhodies, stuff like 'Captain Jack', augustinii maybe had a bit of leaf burn But seemed to cope with the absolute degree of cold better. They only showed damage relative to the absolute low hit for the season, not the fact the average for the month was so bad.

So I would say if a rhododendron cultivar or species variety is absolutely hardy to temperature x, it isn't going to be mind one day at temperature x or 3 weeks at temperature x. Again, provided it is fully established, and not dessicated by some kind of winter drought. (not a problem here, if anything the winters in my garden are extra-rainy by east coast US standards)


Fri Feb 03, 2017 10:59 am
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Joined: Sat Jul 09, 2016 9:16 pm
Posts: 46
Location: Klaipeda Lithuania 6B zone 55°42 N
Post Re: Rhododendron rex
I see the point. This autumn in November we had an unexpected cold dip down to -11 C during single night from positive temperatures (I did realised this only when checking my temperature logger readings, as the day temperatures were above freezing again and the forecast was something like -7C), which in turn caused devastating damage to the still new growth on "Edith Bogue" and Rh. "Teddy Bear", while no other evergreen plants seems were affected.


Fri Feb 03, 2017 11:58 am
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Joined: Sun Mar 24, 2013 2:37 pm
Posts: 219
Location: Halifax, NS
Post Re: Rhododendron rex
Arturas - The damage on Teddy Bear, was that a late flush that got damaged? If so I'm not surprised even though we've never seen damage on it . One wonders what its parentage is, it's often said to be yak x bureavii or the reverse. My hunch is the west coast "bureavii" used was a hybrid, wouldn't surprise me if the yak was one as well.

'Edith Bogue' is an absolutely useless selection for cold areas. No matter what the low temp it always dies in March or April with bark sliding down the trunk. The exception has been one whip in the city that has hungon since 2013, it is so bad-looking I dare not post it - might have 10 leaves at best. Better '24 Below' (a gross exaggeration that temp, Celsiuis or Fahrenheit!) and 'Bracken's Brown Beauty'. 'Victoria' is useless too, that city hardly knows winter.

We are notorious for sudden temp plunges along the coast and some rhodos do not like that one bit. Believe or not the Finns say BVT is particularly susceptible if early in the year. The worst and most untimely plunge was in the late 70s, we heard Boston had dropped from something like 58F to -9F in a matter of hours on Xmas Day so we braced ourselves knowing the front was headed our way. The damage at the Arnold was bad, I recall the propagator told me the old kaempferis froze out. On Boxing Day the temp was 55F here and drizzly, by about 8pm it was -4F, a decorum with a sizeable trunk froze to the ground as did a circa 8-12ft rex (hard to tell as this big one was on a slope) - both suffered severe barksplit, the decorum tried to send out new basal shoots but died the next winter. We've had similar plunges in January or February with little consequence so I assume the autumn must have been very mild when rex got hammered. A very similar event took place on the west coast in the 50's and again in the early 70's and Eugene, Oregon dropped to -12F.


Fri Feb 03, 2017 2:33 pm
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Joined: Wed Feb 13, 2013 11:56 pm
Posts: 409
Location: Seekonk, Massachusetts USA, USDA zone 6b
Post Re: Rhododendron rex
John, my gut tells me your summer soil temperatures are too cool for southern magnolia. My Edith Bogue did fine the last two winters and last winter we hit -13F (-25C). In our area EB seemed to perform best and beat out BBB, V and LG.

Old video
https://youtu.be/yHCJ7LmmXqU


Sat Feb 04, 2017 9:13 am
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Joined: Sat Jul 09, 2016 9:16 pm
Posts: 46
Location: Klaipeda Lithuania 6B zone 55°42 N
Post Re: Rhododendron rex
John - yes it was the late flush of "Teddy Bear", actually it was a single leaf :D - other leaves were totally intact . Regarding EB I have experience which could be placed in-between ones of Tom and John. EB survived first winter in my country last year in open, but lost 80% of leaves at the end, even the minimum temperature was only - 16.9 C one night - logger was placed next to EB. But the plant recovered quite well and in the autumn was looking much better than a year before - larger and more dense (it is on one of the pictures I posted in this thread earlier). I think damage to young shoots during the winter improved a bit a 'leggy' habit of EB making it more compact and dense. I may try other clones, but it is impossible to find in my country - the EB I have was posted from UK 2 years ago...


Sat Feb 04, 2017 9:58 am
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Joined: Sat Jul 09, 2016 9:16 pm
Posts: 46
Location: Klaipeda Lithuania 6B zone 55°42 N
Post Re: Rhododendron rex
I have received the seed package from ARS seed exchange yesterday - it looks I have acted like a fat boy in the candy store:
17-30    h.p.   'Sandra Hinton' X sinofalconeri 00/188
17-44    h.p.   "Falcon's Crest"1 X 'Laramie'
17-50    h.p.   "Golden Horseshoe"('Papaya Punch' X 'Casanova') X macabeanum, Bones3
17-59    h.p.   [(yakushimanum x lacteum) x (yakushimanum x macabeanum)] X 'Laramie' Goal: large leaves, indumentum
17-73    h.p.   (yakushimanum x wardii) X macabeanum  Goal: yellow flowers, indumentum
17-71    h.p.   (yakushimanum, o.p.#1)3 X sinofalconeri, RSF00/188  Goal: large leaves, indumentum
17-102    h.p.   ‘Hardy Giant’ X hodgsonii, RSF 76/191
17-104    h.p.   'Hardy Giant' X rex ssp. fictolacteum, RSF77/417
17-144    h.p.   (brachycarpum 'Tony Law' X rex ssp. fictolacteum) X 'Babylon'   Goal: earlier flowerer, improved 'Babylon' foliage
17-229    h.p.   'Many Moons' X macabeanum (Finnerty Gardens, University of Victoria, B.C.)
17-262    h.p.   brachycarpum var. tigerstedtii X eximium, RSF 77/737   Goal: big leaf hybrid
17-263    h.p.   brachycarpum var. tigerstedtii X sinogrande, RSF 77/737   Goal: big leaf hybrid
17-264    h.p.   brachycarpum var. tigerstedtii X sinofalconeri, RSF 00/162   Goal: big leaf hybrid
17-265    h.p.   brachycarpum var. tigerstedtii X sinofalconeri, RSF 00/188   Goal: big leaf hybrid
17-268    h.p.   'Francesca' X basilicum, Flavell (FGW)   Goal: big leaf hybrid
17-272    h.p.   'Katherine Dalton' X basilicum,   FGW Goal: foliage
17-273    h.p.   'March Madness' X macabeanum, Bones #1
17-278    h.p.   'Spellbinder' X "Kathy Bones"
17-319    h.p.   lacteum X macabeanum
Actually I marked some of the seeds as substitute, but got both. Now I facing a weekend to spend on the preparing the containers for germination.


Sat Feb 04, 2017 10:46 am
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Joined: Mon May 30, 2016 3:16 am
Posts: 186
Location: Missouri USA
Post Rhododendron rex
Arturas - congratulations on your seed acquisitions.


Sat Feb 04, 2017 7:59 pm
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Joined: Sun Mar 24, 2013 2:37 pm
Posts: 219
Location: Halifax, NS
Post Re: Rhododendron rex
Arturas - You might find some crosses of interest on our local society's seedex, lots of hardy material.

http://www.willowgarden.net/2017%20ARHS%20SeedEx/ARHS_2017_SeedList.pdf

john


Sat Feb 04, 2017 10:37 pm
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Joined: Wed Feb 13, 2013 11:56 pm
Posts: 409
Location: Seekonk, Massachusetts USA, USDA zone 6b
Post Re: Rhododendron rex
Arturas,

Nice list of seed. I too ordered many of the same seed packs.


Sat Feb 04, 2017 11:44 pm
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Joined: Sat Jul 09, 2016 9:16 pm
Posts: 46
Location: Klaipeda Lithuania 6B zone 55°42 N
Post Re: Rhododendron rex
Thanks everybody for the comments on my acquired seed list. Will see if I will mange to grow them. John, as I understood the seed in your link are available only for the NS chapter of ARS ?- I am non-chapter now as there are only two Lithuanian members ;). Here goes my setup for germinating the seed:
First a layer of drainage material - Ceramsite
Image
Then a layer of sphagnum peat and sand
Image
and finally the thin layer of milled sphagnum moss
Image
et voilà.... - this a photo of the second tray - I needed to prepare two ....
Image
I am not sure if doing everything right way.... still placed two trays on a window sill facein southwest, temperature should be ~20C as well, but no bottom heat


Last edited by Arturas on Mon Feb 06, 2017 11:16 pm, edited 1 time in total.



Mon Feb 06, 2017 3:24 pm
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Joined: Mon Oct 29, 2007 4:06 pm
Posts: 4501
Location: Islington, London UK
Post Re: Rhododendron rex
You have some problems with your image code there, Arturas, and I can't figure out how to fix them.

The images are not displaying in the thread. There are small icons that say "image".

I think you have linked to images that require permission or password access to be displayed. When I paste the URLs directly into a browser, I get a "no entry" sign icon.

_________________
51º33'07"N x 0º07'21"W
43m (142 feet) ASL


Mon Feb 06, 2017 6:42 pm
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Joined: Sat Jul 09, 2016 9:16 pm
Posts: 46
Location: Klaipeda Lithuania 6B zone 55°42 N
Post Re: Rhododendron rex
I hope it is fixed


Mon Feb 06, 2017 7:22 pm
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Joined: Sun Mar 24, 2013 2:37 pm
Posts: 219
Location: Halifax, NS
Post Re: Rhododendron rex
Arturas wrote:
. John, as I understood the seed in your link are available only for the NS chapter of ARS ?- I am non-chapter now as there are only two Lithuanian members ;).


Arturas - I think most of the orders from members are in so you can safely order now even though it says non-members after 1 March. And Sharon can do Paypal.

john


Tue Feb 07, 2017 3:03 am
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