Trees in Pots?

October 10th, 2011

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

   A few enterprising folks plant their pots with perennial flowers, herbs or vegetables.

Evergreens make up a whole pot garden in this display at Bartholdi Park in Washington.

   But hardly anyone grows big stuff in pots.

   Most shrubs, evergreens and even trees do fine in pots.

   Converting a few of your flower  pots into a home for, say, a couple of evergreens by the front door, gives you more mileage than just packing them away in the garage.

   “You can grow pretty much anything in a container so long as the container is big enough,” says Jonathan Wright, a horticulturist at Chanticleer gardens in Delaware County (www.chanticleergarden.org).

   In some ways, growing woody plants in pots is easier than growing them in the ground.

   The most elemental reason for planting woody plants in pots is lack of in-ground space.

   “It lets you have plants where you otherwise couldn’t,” Wright says.

   That includes decks, patios, concrete pool aprons, unused parking and driveway asphalt and atop just plain awful ground, such as root-infested areas under big trees and horrid rocky or clayish soil.

   Wright also likes the impact that a striking shrub or specimen evergreen makes in a pot.

   “It gives you a good sense of scale right off the bat,” he says. “You get better effect, drama and height quickly.”

   Especially when you use an unusual or colorful pot, the plant becomes a focal point instead of just another plant in the garden.

   Err on the big side when it comes to pot size. Woody plants are bigger and have more extensive root systems than most flowering herbaceous plants and so appreciate extra elbow room.

   “Think big,” says Wright. “I’ve seen people use bathtubs as containers.”

   Painted trash cans, half whiskey barrels and boxes constructed out of wood or recycled plastic timbers are all good options.

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

Thick foam pots withstand our winters much better than terra-cotta or ceramic.

   Also go with sturdy pots 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.

   Another benefit of woody plants in pots is that they’re portable. You can wheel them around to change your garden’s look. Or you can take less hardy species inside in winter.

   Determined to grow lemons? Lusting over that red-leafed loropetalum you saw at that nursery in North Carolina?

   Grow that kind of non-hardy fare outside in summer, then move it to a garage or sunroom for winter.

   Most plants hardy to our area withstand winters outside in pots without protection. All they need is a little water during dry, thawed-out spells — especially evergreens.

   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.

   A good rule of thumb: winter-protect anything that’s rated only to our cold-hardiness zone and up. We’re Zone 6 on the plant hardiness labels. So anything Zone 5 and lower should be fine without winter protection. Anything Zone 6 and up will appreciate some warm help or going inside for winter.

   During the growing season, the main job 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.

   Three more advantages:

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

   * Pot growth also all but eliminates weeding.

   * And bunnies, groundhogs and voles have a harder time gnawing the bark and roots of potted plants than ones growing right at their feet.

   If/when your plants get too big for the pots, they can be 1.) moved to a bigger pot, 2.) pruned back (roots and top growth), or 3.) planted in the ground.

   Potted evergreens look great lit up for the holidays on either side of any doorway.

   Vines like clematis and honeysuckle in long planter boxes, supported by a trellis, add fast screening to decks and patios.

   Japanese maples, roses, hydrangeas and weeping dwarf conifers all look great in pots, especially when underplanted with color-coordinated flowers.

   Think of the possibilities, and you’ll run out of pots before you run out of plants to try.

   Here are 10 varieties to consider that make striking pot specimens…

   1.) Cutleaf weeping Japanese maple.The leaves are lacy, and the habit is umbrella-like. Particularly nice are red-leafed ‘Tamukeyama,’ ‘Garnet’ and ‘Red Feather.’

A young Japanese umbrella pine.

   2.) Purple smokebush. Rounded leaves of purple-burgundy on a multiple-stemmed mini-tree. Gets creamy-white flower “puffs” in late spring.

   3.) Japanese umbrella pine. A pyramidal evergreen with unusual needles that look like fleshy light-green straws spraying out of the branches.

   4.) Weeping Serbian spruce ‘Pendula Bruns.’ A little hard to find, but it’s a slow-growing, needled evergreen with a weeping habit and silvery blue needles.

   5.) Dappled willow ‘Hakura Nishiki.’ A part-shade mini-tree with multiple stems and heavily variegated new growth that makes the wispy plant look like it’s almost white.

   6.) Japanese plum yew ‘Fastigiata.’ A deer-resistant, dark-green, soft-needled evergreen that looks like a yew except the needles are bigger and flatter. This one grows into a skinny column.

   7.) Elderberry ‘Black Lace.’A large, fast-growing shrub that puts out heavily dissected leaves of nearly jet black. Gets pinkish-white flower clusters in late spring.

Foliage of elderberry 'Black Lace.'

   8.) Tree-type hydrangea. Hydrangeas that grow upright to 6 or 8 feet and get cone-shaped flowers from mid-summer to early fall. ‘Limelight’ blooms pure white; ‘Vanilla Strawberry’ and ‘Pinky Winky’ are bicolor white and pink.

   9.) Sumac ‘Tiger Eye.’ A 6-foot deer-resistant shrub with heavily dissected leaves of neon gold all season.

   10.) Tree peony. A woody type of peony that gets the same, large, rose-like spring flowers as the more familiar herbaceous peonies, only these don’t die back to the ground in winter. Growth habit is like a small, leaf-dropping tree.