cornus kousa hardiness

Discussion in 'Cornus (dogwoods)' started by Unregistered, Sep 17, 2005.

  1. My wife and I recently moved to zone 4b (-25 F) in the foothills of the White Mtns of NH. Cornus florida apparently is out of the question. But, has anyone had consistent success with cornus kousa in zone 4? Any observations also on the hardiness of pink/red cultivars vs the white ones?

    In searching the internet, most growers/retailers list zone 5 as the hardiness limit but occasionally I see zone 4 noted. Some only rate cercis canadensis as a zone 5 but just as many a zone 4. The information regarding hardiness of many species seems quite suspect and unreliable, or just plain not determined for sure.

    bobw
     
  2. deet

    deet Member

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    Still considering a dogwood? I'm new to this forum and just saw your post. We're in Zone 4a, west of the Adirondacks, and never had any luck w/ kousas. They freeze to the snow line. I'm interested in hearing about the hardiness of the Rutgers hybrid 'Galilean', which is allegedly Zone 4 hardy.
     
  3. NHBabs

    NHBabs Member

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    I'm south of you, a bit north of Concord. We're in a valley, so often get later spring frosts than the surrounding areas at higher elevations. I have a couple of unnamed Cornus kousa that are about 6' tall, and have been in the ground here 3 or 4 growing seasons. Both have done well so far. We've had temperatures to about -20 F most winters and to -22 one winter. There has been no tip dieback, and last spring one of them bloomed for the first time. It was a bit warmer winter than usual, though, so I'm not totally sure they will be bud-hardy every winter. I'll probably give them a few more years before I spend the money on named varieties.

    "Some only rate Cercis canadensis as a zone 5 but just as many a zone 4." I used to live where Cercis canadensis grew wild and really wanted one here in NH, so did a bunch of research on hardiness. Different strains and cultivars have different degrees of hardiness, probably due to where the genetics of that particular type originated. (Exposure to cold temperatures over time will presumably select for greater cold hardiness.) I found a couple of seed strains that are supposed to be hardy into zone 4, and one of my neighborhood nurseries had a couple of trees of one of them. The owner told me that he gets tip dieback some years, but the plants were in mulched pots, so I'm not sure if that affects tip dieback or only overall survival. Anyway, my Cercis is in its second winter and doing well so far. I know we've had warmer than usual winters, but I also know that there are a bunch of Cercis at Plymouth State U. about an hour north of me here. I tend to use the PSU campus plantings as a way to test hardiness - if a particular type of plant looks rotten at the end of the winter there, I probably don't want to be looking at it every day at home.

    Hope this was a help.
     
    Last edited: Jan 12, 2007
  4. Ron B

    Ron B Paragon of Plants 10 Years

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  5. Soferdig

    Soferdig Member

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    I have a 'Satomi' in my garden here in Montana. It is unprotected and does wonderful over the last 2 years. We have had temps this year -22F, and a long -25 last year and it did just fine. The red large brachts were georgeous this last year. I also have 5 other Cornus alterfolia 'Joyeus summer', 'Argentea', (both of these have unique leaf color instead of dramatic flowering) and an unknown save at end of year 7 years ago.
     

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