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The Cold Facts on the Freeze


By Paul James

First, the good news. The vast majority of landscape plants will weather the weather unscathed, despite the brutal cold this week. After all, most are completely dormant and hardy enough to withstand temps at or below zero. In other words, at least 99% of your plants will be fine. Now let’s talk about the 1%.

Trees and Shrubs

Some early spring-flowering trees such as saucer Magnolias started producing flower buds last week, and those buds will get nipped. The same may well be true of Forsythia, quince, and quite possibly, some Hydrangeas. The plants themselves, however, should be fine.

I’ve also seen leaf buds swelling on numerous maples such as ‘October Glory,’ and those buds will take a hit as well. But thankfully, those same trees produce secondary leaf buds that will emerge a few weeks later than usual.

Plants that are on the edge of hardiness — Italian Cypress, Aucuba, Gardenia, and variegated Privet come to mind (and maybe Mimosa) — may not fare so well. Time will tell.

The top growth of Crape Myrtles could take a hit as well, resulting in dieback of their branches. But their root balls are hardy and they’ll bounce back with new growth from their bases in spring. Loropetalum will likely suffer the same consequences. And sadly, the top growth of figs will almost certainly die back to the ground.

Boxwoods and other broad-leaved evergreens may suffer from tip burn, especially if they were pruned or fertilized late last year and new growth never had a chance to harden off completely. The damaged foliage can be removed in early spring.

Potted Plants 

Plants in pots, even the hardiest among them, are especially vulnerable because they’re more exposed, and that increases the likelihood of their roots freezing solid. (When water freezes around plant cells, that’s okay. But when water within the cells freezes, that’s bad news.) You can move them into the garage, or just plan on replanting in spring.  

Spring-Flowering Bulbs

Daffodils, crocuses, and grape hyacinths started emerging several days ago in my garden, but I’m not worried. Their leaves may turn brown, but their flowers are fine and will bloom on que in the weeks to come.

So, in Conclusion

Unfortunately, there’s not much that you can do to protect your landscape plants when temps drop near or below zero. After all, blankets only provide a few degrees of protection, so don’t even bother trying to cover your plants. And there’s no need to water the top growth to create an insulating layer of ice because thankfully the ice — and in many areas snow as well — is already there.

And there’s a good deal of soil moisture in the ground, which is a good thing, especially in the case of conifers and evergreens, because wet soils hold more heat than dry soils. So cross your fingers, hope for the best, and let’s all wait to see what happens.

One final note: Wind chills have no effect on plants. That’s a measure of how cold it feels to the exposed skin of humans.

Happy gardening, ya’ll. Stay warm.

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39 responses to “The Cold Facts on the Freeze”

  1. Craig Jenkins says:

    a week ago, had installed a young Oklahoma Red Bud.
    It was well mulched by your planting crew.
    What are its watering needs in this weather?
    Thanks!

    • Paul James says:

      Assuming our crew watered it at planting time or advised you to shortly thereafter, you shouldn’t need to water until late next week. The tree is fully dormant and hardy enough to withstand this blast of cold weather.

  2. Julie B Miner says:

    What about climbing rose?

  3. Diane Fell says:

    I have 2 potted dwarf Alberta spruce. Do you think they will survive the 4 degree nights?

    • Paul James says:

      Can you move them into the garage? The top growth will be okay, but if the roots freeze solid they won’t survive.

  4. Rhonda Wilson says:

    What about pansies?

  5. Christy says:

    I’ve been keeping my impatients in the garage when it hit below 40. This morning when I turned on my grow light I noticed it acting like it needs water. I haven’t been heating the garage so would this be a sign it to cold or that it really needs water??

  6. Terry says:

    We had Southwood plant Spartan Junipers and Emerald Collonade Hollies in November. I’ve been watering weekly as instructed but should I water this weekend with temperatures so low?

    • Paul James says:

      There’s quite a bit of moisture in the soil already, so they should be fine, especially since you’ve been watering regularly.

  7. Skylar McCormick says:

    Planted 3 “cold hardy” Windmill Palms last year. The blame for this historic cold falls on me.

  8. Nancy F. says:

    Our Loblolly pine needles are covered in ice – do we leave them alone or tap the branches to try and break away the weight of the ice?

  9. Kimberly Jones says:

    How about potted cactuses?
    And thank you for all the other wonderful information!!

  10. karenryanwhite8 says:

    Southwood’s planted some Okla and Rising Sun Redbuds last fall. I noticed buds on these trees. Did this freeze ruin the display these little trees put on in spring?

    • Paul James says:

      Chances are the flower buds will get zapped by the single-digit temps that are on the way, but the trees themselves should be just fine.

  11. Susan Grapengater says:

    I have a Lenten Rose that is/was in full bloom-should I cover it for the next week?

  12. Zooey says:

    I have a large Arp Rosemary planted in the garden. Is there anything that can be done to protect it from the freeze? Thank you

    • Paul James says:

      Not really. A thick covering of mulch may help, but we haven’t seen low temps like these since 1983, when basically all Rosemary died. Harvest now!

  13. Caroline Johnson says:

    Will the tender new growth of my Showy Stonecrop be okay?

    • Paul James says:

      It’s quite hardy, so even if the top growth takes a hit it should rebound. The accumulation of ice and snow is a plus because it insulates the plants and the soil.

  14. Leslie Sipes says:

    I have several different varieties of heuchera that have been in pots for years. Any chance they will survive? My other concern is my orange rocket barberry in containers.

  15. Gaurav says:

    Hi Paul,

    I have a young pomegranate tree that I planted last spring. This blast of cold seems beyond its survival range. What are its chances of survival?

  16. Gaurav says:

    Paul,

    I have a young Arbequina olive tree potted and safely inside. The staff at Southwood advised me that an Arbequina can withstand Zone 7 cold and that there are several here in Tulsa. From everything I’ve read on the web, the consensus is that even cold hardy Arbequinas don’t survive this cold. What’s your view? Do you think my Arbequina would have survived this blast of Arctic temperature had I put it in the ground?

  17. Sherry Graham says:

    Wondering about azaleas during this long period of cold temps?

  18. Joani Whipple says:

    Hi Paul, We purchased a Misty Southern Highbush Blueberry and an Ice N’ Rose Helleborus in mid January from Southwood. They have only been in the ground for a few weeks. They are well mulched. Do you think they will make it?
    Thank you for helping the many worried gardeners out there! We appreciate you!

  19. Helen Kannady says:

    Every year Proven Winners lists about a dozen new perennials for the new year. They are available for sale on line but the shipping is prohibitive. Why are they never available at local garden centers anywhere in eastern Oklahoma or western Arkansas. Would be so happy if they were available here. If not why not?

    • Paul James says:

      New releases are often limited and unavailable to retailers for the first few years. We buy a lot from Proven Winners, and if you have specific requests, we may be able to special order items for you.

  20. Caroline Johnson says:

    Our variegated privets look so sad, leaves are brown 🙁 Will they be okay?

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