Brrr! What NOT to Prune in Winter

Right now it’s major big time pruning season here in Northern Cali. I’m cutting back hardy perennials, roses, fruit and other dormant trees and ornamental grasses. But there are a few things I’m leaving alone for the time being. A lot of my favorite plants are frost-tender and can be killed by a stern frost this time of year. For some of these plants, the old, dead foliage and stems are providing just an extra degree or two of protection for the tender new buds and shoots coming along for next year.
Dormant Mexican Bush Sage - Salvia leucantha
Dormant Mexican Bush Sage or Salvia leucantha
New growth on Mexican Bush Sage Salvia leucantha
See the tender new shoots inside? The old stems help protect them from frost damage.

If you can hold off, don’t prune these frost-tender plants until after last frost, which here in Humboldt County is around mid-May:

Salvia leucantha or Mexican Bush Sage (and other tender sages) Fuchsia thymifolia or Fairy Fuchsia Lemons and other citrus Brugmansia/ Datura or Angel’s Trumpet Loropetalum chinense or Fringe Flower Ginger Tibouchina urvilleana or Princess Flower Passiflora or Passionflower Vines Pelargoniums or traditional Geraniums (Hardy Cranesbills/ true Geraniums are fine to cut back now) Polystichum polyblepharum or Tassel Fern Dicksonia antarctica or Tasmanian Tree Fern

Further reading:

Pam Penick from Digging has some tips on what to do with tender plants and particularly Agaves that have frozen and become mushy. Rebecca Sweet from Gossip in the Garden has a great tutorial on protecting tender plants from the cold.

Comments

  1. says

    Gen, great advice as always! On a slightly different note I thought you may be able to advise me on something I feel I should already know. Everyone knows it’s bad news to be cutting on woodies when it is precipitating, but I’m surprised I can’t recall hearing anything in regards to how this might apply to perennials. It’s fall cleanup/major cutting back time here in Colorado and I’m wondering if cutting them back on a rainy day should be avoided. Knowing your climate I would think a.) you’ll surely know (as should I for that matter, having lived there!) and b.) it would be nearly impossible! Thanks for sharing the depths of your wisdom!

  2. says

    Eve, thanks!!

    I think it’s only an issue on things that are known to have fungal or bacterial problems or trouble healing from big cuts, like rosemary, ceanothus, fruit trees, roses, and almost all conifers. Conifers of course transmit their sap differently and so heal from pruning less well.

    If you were going to make cuts larger than a quarter around I’d probably wait for a dry day too, if possible. Though I’ll be perfectly frank – we get so few of those dry days in winter that I try to just spray my saw with rubbing alcohol (leave on for a minute to kill germs, then wipe dry) when moving from plant to plant and don’t worry too much about dry days.

    It is nice if it isn’t actively raining and splashing though. I think a lot of the worst bacteria are actually natural bacteria in the soil – they just aren’t meant to be in open tree cuts.

  3. Ellen Selig says

    We purchased a home this summer here in Norfolk, Va and now have an angel trumpet that needs pruning. Is this the right time for our zone? And home low do I go to do it properly? Thanks, Ellen

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