container plantings in winter

With winter approaching, it's time to look around at any container plantings you have and think about protection.  Some plantings can be kept looking good throughout the winter with little protection needed, while others may go dormant and/or may require kinds of protection that render them less useful for ornamental purposes.

Even shrubs, trees, and hardy perennials need extra protection if grown in containers, because containers make roots more vulnerable to freezing, and may as well lack sufficient drainage in periods of heavy rainfall.  The problem is inversely proportionate to container size.
A giant container-- something at least the size of a large garbage can- may need little or no extra care, though recently installed plants may appreciate a draping of protective fabric if freezing temperatures threaten.
Smaller pots, down to gallon size, should be grouped next to or behind larger pots, or next to the side of a building.  Plants that will go dormant can be mulched with straw, if this is not an aesthetic problem.
Plants in pots smaller than gallon size are very unlikely to make it through the winter outdoors.  They should be transplanted to larger containers, or taken indoors.

Make sure that all your planters have adequate drainage holes.  This is important at all times, but especially in rainy weather.  Well-draining planting medium is important; for plants less tolerant of sogginess, extra perlite, woody material, or pumice can be mixed with the soil.
The popular idea that broken pottery or gravel at the bottom of a container promotes drainage is not, unfortunately, correct, and can in some instances even be detrimental.  Make sure that any dishes under pots are removed-- those dishes are most useful for indoor containers; in winter they can cause a plant to drown.  

Wooden containers generally provide excellent drainage, and are not subject to shattering from freeze/thaw cycles.  Metal containers, if properly slotted for drainage, can also be good.  Ceramic containers, often the first choice aesthetically, may be vulnerable to cracking unless they are labeled "frost-resistant"-- which generally doubles the price.  Terra cotta containers, because they absorb moisture, are particularly vulnerable to winter damage.

Larger pots- those between gallon size and garbage can size-- should be huddled together, and can be individually wrapped in bubble wrap (pot only), sometimes with burlap to protect the plants above the soil.  (Be warned that plastic wrap kept consistently over the tops of plants can seal in moisture and lead to fungal diseases or rot.)

For some outdoor plants in containers, rainfall is the major challenge of winter.  Some of these will overwinter better if kept under the house eaves, or even turned sideways.  On the other hand, some winter fatalities in the ground and in containers, result from desiccation that occurs when the soil freezes and plants cannot take up moisture.

Garden centers often promote "annual" plants for container use, but in fact many of these are tender perennials.  Some of them can be overwintered indoors.  Some can be kept actively growing in a sunny window all through the winter, while others may go dormant.

Tender fuchsias are the kind used in hanging baskets, with large flowers- different from the hardy fuchsias, which are more erect shrubs with smaller flowers.  Tender fuchsias will go dormant, and will not surive the winter outdoors, but can usually be overwintered if wrapped in burlap and kept in a garage or other sheltered location.

Cannas are mostly pretty tender here, though they can sometimes overwinter in the ground in a sheltered location with extra mulch and blanketing with burlap for freezing periods.  However, a canna can be overwintered in a container indoors.  With enough light and warmth, the plant may continue to bloom until December, and will then be an attractive foliage house plant until spring.

Cordyline is a tender plant that can easily be mistaken for Phormium (New Zealand flax), except that the leaves of Cordyline grow in a whorl (like Yucca), whereas Phormium leaves occur in "fans".  Cordyline will not as a rule make it through the winter in our area, but can overwinter happily as a houseplant, like its cousin the Dracaena.

At North Coast Natives, I offer custom-designed and readymade container gardens, with an emphasis on perennial and evergreen material for containers that look good and provide color year-round.  These may include brightly-colored foliage and some winter-blooming plants.  Contact me for photos or an appointment to view samples.  I can design and install single containers or whole suites of containers for your home or business, and offer rotating container arrangements designed for business settings.