Unprecedented cold snap

Discussion in 'Outdoor Gardening in the Pacific Northwest' started by Margot, Jan 12, 2024.

  1. Margot

    Margot Renowned Contributor 10 Years

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    Apparently it has been decades since the Pacific Northwest experienced such a cold few days as we are living through right now. Of course, the impacts on people, traffic and infrastructure are of greatest concern but we gardeners worry about how the sudden cold, following a rather warm fall and early winter, will impact our treasured plants and our gardens.

    This, on top of an unusually dry summer, is pushing many plants to their limits. Are Plant Hardiness Zones even relevant anymore?

    I'm starting this thread for everyone interested to share their stories - the conclusions to which may not be known until spring arrives or even beyond.
     
  2. Ron B

    Ron B Paragon of Plants 10 Years

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    I've been at my current location on an island in the Salish Sea for 3 years. Since I moved here, I have seen 5F on my automobile dashboard outside temperature display. Which continues to appear to be giving accurate readings on numerous other occasions, via comparison with other sources. And as a result of the involved cold episode had an outdoor house wall spigot - that had a Styrofoam faucet cover on it - freeze and produce a cascade of ice that extended to the ground. (The plumber thought this one faucet failed among many others that did not because the supply line for it came out of the unheated garage). This was during one of the previous winters and not recently. Also, it could perfectly well have gotten colder than 5F here - that reading was what was being displayed inside the car when I happened to see it.

    As a result of these conditions local cordylines and phormiums were leveled. Including an example of the latter that was maybe 7 ft. tall, apparently was not able to grow back. Windmill palms were burned and slow to recover. Certain Asian mahonias were also scorched, a long-established Azara microphylla apparently died. As did a percentage of ceanothus. These last three sets were among unsheltered plantings in the mud of the Skagit Flats.
     
    Last edited: Jan 13, 2024
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  3. Margot

    Margot Renowned Contributor 10 Years

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    5F is pretty chilly alright! What hardiness zone would you say you are in?

    My min/max thermometer hadn't gone lower than -2C (28F) for the past several years but it's down to around -11C these days. Maybe I'm not in Zone 8 after all.

    I threw sheets over a couple of phormiums but I don't think that will be enough to protect them.

    Between dry summers and cold winters, my list of dependable plants is definitely growing shorter. I've started a list of things that thrive even under challenging conditions and will plant more of them rather than try new ones.
     
  4. Ron B

    Ron B Paragon of Plants 10 Years

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    I'm designated USDA 8 using the current USDA zone search tool and mapped Sunset 5 by the last edition of the Sunset Western Garden Book. The damage to cordylines and phormiums was apparent even in a variety of Seattle locations despite the urban smog dome often making lows higher there than in communities to the north and east. In addition to existing natural circumstances, such as hyper-maritime neighborhoods of the south half of Puget Sound having Californian winter minima.

    Teens F. were forecast by the National Weather Service for my area last night and the night before. If it ever got into the single digits, I have not learned of it yet.
     
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  5. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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    That's still well within the remit of zone 8; remember the zone number is based on the average winter low of a long series of winters, and the cold ones can be a lot colder than the average, just as the warmer winters are well above the average. In our last really severe winter (1981/82), zone 8 sites were getting temperatures down to -16°C to -18°C, some even colder than that, while zone 7 areas of the Scottish Highlands and Denmark were getting down to -25°C to even -30°C locally.
     
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  6. Ron B

    Ron B Paragon of Plants 10 Years

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    Saw it stated in an article on recent conditions at Mount Baker and vicinity that it was the coldest there it had been in 14 years.
     
  7. vitog

    vitog Contributor 10 Years

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    In the Vancouver area (YVR temperatures) we have just had three very cold winters in a row, with a minimum temperature of -15.3 C two winters ago, -13.5 last winter, and so far this winter: -13.4 yesterday and -13.6 or lower today.

    That -13.6 drops the 30-year average low to -9.05 C, which still keeps this area in USDA Zone 8b (the transition between 8a and 8b is at -9.4 C). However, many (maybe most) plants react to current year minimum temperatures and don't keep track of averages. So, I expect a lot of damage this winter, probably significantly more than last, because we've had two nights of extreme lows already. My only worry is the 20 subtropical Feijoa bushes that I have. Most of them were damaged during the previous two winters and will probably sustain significant damage this winter. I only protected three of the plants and left the rest unprotected.
     
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  8. Ron B

    Ron B Paragon of Plants 10 Years

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    Yes - it only takes a few hours below a given plant's bottom floor for it to be nailed. And pineapple guava is generally on the edge of its tolerance in the Salish Sea area. Another plant for hyper maritime sites that usually have high minimum temperatures not seen away from the beach.
     
  9. Margot

    Margot Renowned Contributor 10 Years

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    Quote from Vitog: So, I expect a lot of damage this winter, probably significantly more than last, because we've had two nights of extreme lows already.

    I’m starting to think that plant hardiness guides are not really that much use to me. Knowing that a particular plant (like Phormium) will survive MOST winters isn’t much consolation when it succumbs to a winter like this – and – winters like this could very well become more frequent. We just don’t know. So, from now on, I plan to choose new plants from lower zones and focus my energy on keeping them alive during hot, dry summers.
     
  10. Georgia Strait

    Georgia Strait Generous Contributor

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    It’s amazing what survives in that fast quick natural outflow chill temp we experienced at coast BC

    Certainly NOT my bbq rosemary label plant

    I think it’s the quick temp drop / dehydration / inlet valley outflow / and wind chill (applies to Bellingham WA & Nanaimo / Duncan / Qualicum Parksville too)

    i live and learn - do my best to stay in the blue sky viewpoint - and hope the plants expired quickly (yes I have emotions about my plants :)

    And the south sun just came out from clouds
    Beautiful
     
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  11. Margot

    Margot Renowned Contributor 10 Years

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    Quote: "hope the plants expired quickly (yes I have emotions about my plants :)"
    @Georgia Strait - your comment has brought a lump in my throat.
    My emotions about plant losses have often fluctuated between frustration and anger, not really addressing the sadness.
    Definitely that too; big time loss of plants and dreams of a certain kind of garden.
     

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