Protecting Plants in Cold Weather

As I write this it’s a cold, blustery, rainy November day.  I’ve been working to close down the garden for winter, which although I’ll be doing some trimming & hardscaping projects, means that all other gardening activities have ceased until February or March.  I’ve planted & moved everything in the beds that needed it, I’ve planted my spring bulbs, I’ve dug up my dahlias & cannas to be stored in the basement, I’ve removed anything that isn’t staying (giving away plants to new & enthusiastic neighborhood gardeners is a great joy), I’ve put away the hoses & shade umbrellas, and wrapped the large wooden table & bench in tarps.  And one of my last activities was to add some extra protection for new plants, especially those that will stay in containers for the winter.

There are a number of strategies I employ in the garden to help soften the cold blow of winter…

1. I use horticultural fleece, which is a fabric-like material that is air and water permeable, and UV stable.  It acts very much like a fleece a person might wear, but for plants.  It can be cut to length and held down with stones, or stakes, or bricks, or whatever you might have on hand that will prevent it from blowing away.
2. I use really large pots.  For a variety of reasons, I don’t like to use small containers in the garden.  They need to be watered much more in the warmer months, they need more fertilizer, they need more frequent repotting, and they don’t do as well when it’s cold.  Generally, plants in pots left outside for the winter are at least a full zone lower than they would be in the ground.  For example, if you live in Zone 8, your potted plants will experience winter as if you lived in Zone 7.  Larger pots don’t freeze through as easily as smaller ones and mitigate the impact of not being in the ground.
3. I keep more tender plants, in the ground or in pots, close to the house.  Being close to the house means that they are under the overhang of the roof, so they don’t get as much rain.  They also benefit from the reflected & stored sun & heat from the basement walls, which also reduces the impact of the wind.  Winter winds, especially here in Portland, can be frigid & drying — if it’s sunny out (hooray!) it’s usually super cold & windy (boo!).
4. I utilize the exhaust from our furnace & water heater to create a little pocket of warmth that boosts everything kept in that area.
5. I use the plants themselves to protect each other.  If I tuck a questionably hardy perennial next to a dense evergreen, it can act like a wind break and keep temperatures more stable.  If I group together a collection of potted plants, it will help each one do better than if it was solo.

I’ve been thinking about adding a snow gum tree to my garden for some time.  In a fit of last-minute, late-night, wine-induced extravagance, I bought one off the internet.  It’s a cabbage gum, or Eucalyptus pauciflora.  It has the capacity to grow to a range of 12′-60′, which is quite a range!  I plan to grow it in a large pot to limit its potential, and also place it outside my office window, where it cannot live in the ground.  It arrived in very small container, and I didn’t give it much of a head start for root development by waiting until the last minute to add it this season.  To give it the best chance to survive the winter I employed a couple of my strategies …  I planted it up in a large (24″) pot, right up next to the house (East-facing), and wrapped it in fleece.  I wrapped the whole container, and double-wrapped the base of the stem.  We’ll see how it does.  Fingers crossed!

This flowering maple (Abutilon ‘Lucky Lantern’) started out in this spot this past spring as a tiny plant.  It put on some great growth this season, and although it’s a Zone 8 plant, I want to give it some extra protection to help it through the winter until it becomes more established.  I’m mostly concerned with the roots of the plants, as it can regrow from the roots if necessary, so I wrapped the base of the plant and held it with stones.  Its companion in the adjacent pot is a Lithocarpus densiflorus var. echinoides.  It’s fully hardy for us, but needs to stay in a container over the winter so that it can replace an Aster in the spring.  So I potted it up from the nursery pot into a larger ceramic pot, and tucked it against the house, under the overhang, for some extra protection.

The little guy, all wrapped up, is a Renga Lily (Arthropodium cirratum) that’s new to me this year.  I ordered it online from Annies Annuals over the summer, and potted it up from the nursery pot into a larger, ceramic pot.  It’s not yet ready to go into the ground as we’re waiting to plant some areas until after the house is painted, so it will spend this winter in that pot.  I tucked the pot between other pots, against our basement steps which are also covered with a roof, and double-wrapped the whole thing in fleece.  If things get really bad this winter I can grab it and bring it into the basement, but hopefully it’ll do just fine outside.

It’s difficult to see what’s going on in this photo, but it’s basically a bunch of pots tucked together.  Similar to the protecting effect of the wall of a structure, moving your pots together, with the most sensitive plants in the middle, will help them survive a tough winter.  I’ve highlighted the plant I’m concerned about here, which is a Salvia clevelandii.  One of the most amazing scents in horticulture, I’ve only managed the overwinter this once, and then it was soundly defeated by the boots of a construction crew :-/  This year I’m trying it in a container with tremendous drainage, protected by the other pots around it.  Again, fingers crossed.

If things get really bad (we once got down to 9 degrees) I have some extra fleece I can deploy temporarily on plants that are in the ground as necessary (phormium, gardenia, agave).

But at the end of the day, I knew what I was getting into when I set out into passionate gardening … some things won’t make it no matter what, some things are a gamble to begin with, and sometimes your heart will break, but it’s 110% worth it anyway.  And when all else fails, there’s always the lessons from my dogs, Gus & Ernie, who take each day in stride, and spend cold, rainy days like this one snuggled up in their bed napping.