Woody Plants in Winter Pots?

November 16th, 2021

   Most people use their pots for posies – primarily petunias, geraniums, coleus, and other annuals that get planted each May and yanked each October.

Here’s a grouping of dwarf conifers growing in concrete pots.

   Then the pots get tucked away for winter until frost stops knocking at the door the following spring.

   Hardly anyone uses pots to grow woody plants – i.e. evergreens, shrubs, and small trees – even though most of these do fine in pots and sometimes even better than in the ground.

   You just need to address a couple of issues.

   One is pot size. Err on the big side when it comes to that.

   Woody plants are going to grow bigger than flowers and have more extensive root systems, so they’ll need more elbow room than the 14- or 16-inch containers that can support a typical annual or perennial.

   Go with the biggest pot or planter-box sizes you can find (or accommodate), or go the recycling route and convert another container, such as a trash can, a half whiskey barrel, a feeding trough, a plastic tub, even an old bath tub.

   Just be sure you’ve got ample drainage holes in the bottom.

   Also go with sturdy containers that are resistant to cracking and able to take freezing in winter.

   Plastic, foam, concrete, wood, and metal are better materials than ceramic or terra-cotta if you’re letting your pots out all winter.

   Most plants hardy to our area withstand winters outside in pots without protection. All they need is occasional water during dry, thawed-out spells. That’s especially important for potted evergreens, which continue to lose moisture through their foliage over winter.

   Iffier choices are borderline-hardy woody plants, such as nandina, crape myrtle, camellia, Arizona cypress, cherry laurel, and osmanthus.

   These benefit from some winter protection, such as moving them to a protected courtyard, next to a heated wall, or next to a south- or west-facing stone or brick wall.

Even an old bathtub can become a pot for a woody plant.

   A good rule of thumb: treat potted plants as if they’re growing in a USDA Cold Hardiness Zone that’s one zone colder.

   Most of the Harrisburg area is in Zone 6 (some has pushed into warmer Zone 7a), so any plant rated for Zone 5 and lower should be fine without winter protection.

   Anything Zone 6 and up will appreciate some of the warmth aids above… or going inside for winter.

   If you can’t go inside and need more winter protection than a wall-side location will give you, encircle your trees and shrubs once they go dormant with a loose covering of burlap and then stuff this “straitjacket” with insulating leaves. You can do this only with leaf-dropping woody plants, not evergreens, which will resent months of darkness.

   During the growing season, your main job with potted woody plants is keeping the soil damp. Container-grown plants dry out faster than in-ground plants and need to be soaked every day or two in hot, dry weather.

   Those drainage holes in the bottom of pots will make sure you don’t overwater and rot roots.

   Occasional fertilizer is also usually needed since the frequent watering leaches nutrients out the bottom. A half-strength balanced fertilizer (i.e. 10-10-10) every two weeks is a good average.

   It’s a good idea to replace the soil every spring or two, which gives you a chance to check and address circling roots, too.

   If the roots are tightly bound and circling densely around the pot edges, you have two options.

   One is to repot the plant into a larger container.

   The other is to prune off up to 25 percent of the biggest and/or most congested roots, then fray out the remaining roots before replanting.

   Why bother going to all of this trouble? Some of the pluses and advantages of growing woody plants in pots:

   * You may not have room to plant woody plants in the ground but may have locations on patios, decks, driveways, balconies, even roofs.

   * You don’t have to dig holes and deal with the clay and rocks that so many yards have.

   * Woody plants grown in good-quality, light-weight soilless mixes are much less prone to disease.

   * Pot growth all but eliminates weeding.

   * Bunnies, groundhogs, and voles have a harder time gnawing the bark and roots of potted plants than ones growing right at their feet. (Potted plants don’t faze deer, though. They’ll even eat plants out of pots growing next to your front door.)

   * Woody plants in pots are portable. You can wheel them around to change your garden’s look.