Keep outdoor potted plants alive this winter

2005-11-29T00:00:00Z Keep outdoor potted plants alive this winterBy Sarah Robertson Corvallis Gazette Times
November 29, 2005 12:00 am  • 

As those of us with multiple containers on decks and terraces can attest, our typically wet Western Oregon winters often pose a serious threat to the longevity of favorite plants.

Add the threat of a killing frost and the likelihood of horticultural mayhem is pretty darn high.

In my own garden, weatherproof conifers and idiot-proof perennials winter outside without much human help. Most have thrived as container specimens for years without any special protection, other than perhaps a space blanket when extended periods of subfreezing temperatures are predicted.

A road trip to Arizona last spring, however, changed my container landscape considerably. Our family made a road trip to visit my parents, who now live outside Phoenix in a small town that's just minutes from the state's largest cactus and succulent nursery.

What luck!

Despite the good-natured groans from my kids and husband, I wedged some good-sized agaves, several succulents, a yucca and even a few cactus plants into the back of our van for the long (prickly!) trek back to Oregon.

The new additions settled in nicely over the summer. But after basking in the sun and heat of July, August and September, the chill and wet of late autumn prompted remedial action on my part.

The two largest plants, a yucca and an agave, cannot tolerate the constant rainfall of a typical Western Oregon winter. When air pockets in the soil fill up with water, it's tough for arid-loving plants to adapt and root systems typically suffocate.

So I borrowed a neighbor's moving dolly and, with the help of my teenager, moved these containers to a more protected location beneath a large overhang up against the house.

I also rummaged in the shed for all of my winter plant-protection gear: Reemay blankets, blocks of insulated foam, bags of foam peanuts and old shiny silver space blankets.

These can be tucked around and over susceptible potted plants during relatively brief periods of extremely cold and/or wet weather. It isn't visually pretty. But if it saves an expensive plant, who cares?

For hardier shrubs and perennials, the wet can usually be mitigated by making sure potted plants continue to have good drainage.

At our house, just about every pot sits up off a deck or terrace on little clay pot feet. The same effect can be attained by placing containers on bricks or other porous material. The idea is to gain an inch or two of space between the bottom of the pot and the ground, so that containers can continue to drain out any excess winter moisture.

For a single potted plant that's sensitive to excess winter water, cut a circle of plastic sheeting that's about 3 inches larger than the pot's circumference.

Make a slit down the middle and slide the opening carefully down around the plant in question. Drape the edges evenly around the outside of the pot and secure with twine.

This technique worked well for me this spring when my larger yucca and agave specimens needed to be outside for the light, but flinched under the deluge of spring rainfall.

Although a small amount of moisture made it through the center slit, it wasn't enough to suffocate their sensitive root systems.

In general, keeping outdoor container plants alive during the winter months isn't difficult if you keep an eye on shifting temperatures and take quick action when necessary.

Remember: Most container plants die because the roots are susceptible. Instead of being insulated underground, container plant roots are left, well, virtually out in the cold. The following tips should help - keep them handy!

Quick winterizing for container plants

• Dry soil is deadly during a frost. Make sure your container plants are sufficiently hydrated before freezing temperatures hit. Check the soil periodically, especially if your containers are wintering beneath an overhang.

• An ideal place to overwinter container plants is in a greenhouse or coldframe. Otherwise, move susceptible plants into a shed or garage or cozy them up along the south side of your house when freezing temperatures threaten.

• Protect species at special risk of frost damage by wrapping containers with insulated thermal blankets, bubble wrap, space blankets or bales of hay.

• Surround tropicals with a cage of chicken wire and stuff with chopped leaves or straw.

• Consider spraying the foliage of evergreens overwintering in especially windy locations with an anti-transpirant spray to reduce water loss and damaging leaf scorch. Follow product label instructions.

Sarah Robertson, passionate lover of plants, credits indulgent grandparents with helping her to discover the joys of gardening at a young age. She has written a weekly gardening column for four newspapers in Western Oregon, including the Democrat-Herald, since 1986. Robertson is a journalism/horticulture graduate of Oregon State University. She and her husband, Lance, and two young children are attempting to tame a small but rambunctious suburban garden in Eugene. Questions or comments can be sent via the Democrat-Herald, P.O. Box 130, Albany, OR 97321.

Copyright 2015 Corvallis Gazette Times. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

(1) Comments

  1. leanne
    Report Abuse
    leanne - October 08, 2014 6:57 am
    I like the ideas posted. I will try them this year. Last year I brought all plants in doors and the gnats were bad. This year I dont want all in doors. Some I will have to. I found some tricks to help with indoor gnats. I will try them this winter. Thank you.
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