Hydrangea Macrophylla (either a Mophead or Lacecap form bloom) in Zones 3 or 4?

Discussion in 'HortForum' started by Luis_pr, Aug 28, 2021.

  1. Luis_pr

    Luis_pr New Member

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    Dallas/Fort Worth, Texas USDA Zone 7B/8A
    Just wondering if anyone is growing any hydrangea macrophyllas either in the ground or in pots/containers in zones 3 or 4? These zones are typically -shall we say- " incredibly difficult" for Big Leaf Hydrangeas and their roots but someone in Calgary, Alberta who loves them asked me to post if anyone had even tried with some success. Endless Summer advertises their macros as good in zone 4 but not z3. But while winter hardy in z4, I hear some macros may not be very bloom reliable.

    So, let me know if anyone has had any success (only) please. I was personally curious how they would fare in pots and in a heated garage in z3.

    Note: I am just looking for any success stories to pass along. He just wants lacecap macros. I already told him it would be easier to get lacecap smooth/arborescens hydrangea (or paniculatas) but, eh, he does not want those. Go figure.

    Thanks in advance, Luis
     
  2. Sulev

    Sulev Well-Known Member

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    I'm in the zone 5, but maybe it is interesting for you, what I have to say. My neighbor is a great fan of Hydrangeas. She has several different varieties, including a bunch of macrophyllas. Macrophyllas are in containers only. Earlier years she over wintered her macrophyllas in the basement of her house. Plants woke up early, got leggy and she had trouble to acclimatize these in the spring, because they were very sensitive to the sun. Last year she left half of her macrophyllas overwintering into her greenhouse. This is a small greenhouse of poly-carbonate panels, without heating. Those bushes, that were in the greenhouse, were much stronger in the spring and she told, that from now on she leaves all her macrophyllas into her greenhouse for winters. We had -30ºC (-22ºF) several nights last winter, and below -20ºC couple of weeks.
    In zones 4 and 3 temperature lows may get even lower, but if you have container plants and a place to keep them protected from frosts, then it doesn't really matter. Growing season is possibly significantly longer and warmer in Calgary, than here.
    See Compare the Climate and Weather in Tallinn and Calgary - Weather Spark for comparision.
     
  3. Luis_pr

    Luis_pr New Member

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    I will pass the word. I never asked him if he had a greenhouse! Is your friend's greenhouse heated or not? Thanks, Sulev.
     
  4. Sulev

    Sulev Well-Known Member

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    This greenhouse is not heated, it is small, ca 2 by 4 meters, covered with thinnest 2 layer poly-carbonate sheet. During short winter frost it keeps temperatures up ca +10°C compared to the ambient (in case of -30°C outside there is ca -20°C inside). For longer frost periods this difference is even smaller, ca +5...6°C (-20°C out = ~-15°C inside).

    She put some layers of floating row cover on top of her Hydrangeas. Containers are pretty crowded there, touching each other.
    Containers are laying on the ground, catching the natural heat radiating from the ground and trapped under the floating row cover.
    I think, that temperatures in an unheated garage are still warmer than in this greenhouse.

    They say, that those "new" cultivars of macrophylla (Endless Summer and more recent cold hardy ones) are cold hardy enough to survive even in the ground without protection in zone 5. My neighbor found it out by her own test, that over wintering these plant in the cold results stronger growth and earlier blooming, than protecting them from freezing temperatures (her basement is ca +10°C during most of the winter, drops maybe to +5°C or even 0°C shortly for the coldest period). The issue is, that in the basement plants woke up too early and became leggy because of lack of light.
     
  5. Georgia Strait

    Georgia Strait Generous Contributor

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    That’s a fascinating comparison website you link to @Sulev

    One odd condition that happens in Calgary AB (airport YYC) is called a Chinook

    And it is due to proximity of city on east side of Rockies etc

    Anyway - it can warm up in a quick hour — then plunge back down
    Chinook wind - Wikipedia

    and I wonder if that might confuse tender plants like hydrangea

    One thought I have is that hydrangeas are relatively inexpensive floral plant esp around Mother’s Day in spring (May) — so just get a couple to accent the patio (i would carefully transfer to a larger pot and feed water accordingly) and at end of season — see if they last in the garage
     
  6. Georgia Strait

    Georgia Strait Generous Contributor

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  7. Sulev

    Sulev Well-Known Member

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    From the Wiki article I understood, that Chinook is more like a winter nuisance. For container plants kept in a heated garage that should not be a problem, as it is possible to keep relatively even temperature inside the garage. I suppose, that optimal over wintering temperature for macrophyllas is ca +5ºC. Too warm garage can, of course, cause early wake up. But as Calgary is 8.3 degrees southwards of me, there should be much more light in the winter.

    I just visited my neighbors tonight and saw that their macrophyllas are especially lush and in blooms this year. It seems, that they benefit from a bit warmer summer than we usually have.
     

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