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Pre-Planning For Frost
by Marg Flemming
September 2, 2012


September has arrived. Students have started back to class and Labour Day crowds have dispersed. As gardeners we begin to recall the routine procedures we instinctively follow to prepare our perennials and the gardens they occupy for winter dormancy.
It may seem that winter is not yet of real concern to our gardens and their contents. But the first frost occurring later this month, will trigger flowers and trees to begin their slow, relentless decline from typical, vibrant, summer-green botanicals. Perennials will finalize next year's bud set on viable crowns located close to the soil surface sustained by roots extending into the ground beneath. Shorter days have already planted the thought of leaf drop in the minds of deciduous trees. First frosts will encourage them to retire in a blaze of colour. We can expect to be treated to a foliar grand finale.
What should we add to our list of things to do? Though not unexpected invariably the cold season arrives before we are totally prepared. Here are a few routine tasks for which to budget your fall gardening time. 
Canna lilies are a very reliable annual plant that add a bold colourful flare to any garden. These roots can be retrieved from the garden each fall and held indoors for replanting next spring. Some gardeners believe that these tender tropical plants cannot be subjected to the frosts we fear here in temperate North America. But before retrieving the roots of these showy plants, a light frost overnight can actually be an advantage to a root expected to spend the winter in your basement.
As the frost touches the canna foliage, cells die. The tropical tissue is unaccustomed to the cold and not physiologically prepared to survive under these extreme conditions. Invariably some tissues survive - protected by cells that surround them. In a survival tactic, the frost serves to trigger the downward movement of moisture and sap from remaining tissues back to the root. At the same time the soil surrounding the root is warm compared to the chilly air. Soil is an excellent insulator, so the first few nighttime frosts we experience will not adversely affect the tropical root.
When stems and foliage have been completely killed by cold and tissues begin to dry, much of the water and nutrients will have been moved to the root for storage. The roots, now bulked with additional food and moisture, may be lifted for winter.
Store canna roots in a dry cool place for winter. A basement often provides adequate cool temperatures and low humidity. Remember that tropical climates also experience a form of winter that is typified by drought instead of cold. So your cannas, held bare and dry in the basement, will be enjoying all the comforts of home.
Houseplants that have been treated to summer outdoors will not be as forgiving as cannas if allowed to suffer through a frosty evening. Review your roster of houseplants to be relocated indoors before frost is predicted. There may be more individuals to retrieve than you recall. Scrutinize each plant carefully before it enters your sunroom sanctuary. Insects lurk in cracks and under foliage. Once you have taxied them into the house these sneaky pests can pack up and move onto the specimens that have enjoyed summer indoors. Insect hitchhikers love exotic food, and a valuable indoor plant can become a prime target if outdoor pests are not refused entry. Before giving them access to your indoor collection it is wise to sponge introduced plants with soapy water then rinse with a light misting from the hose. Soap clogs the breathing holes of insects and so it makes a valuable non-toxic, environmentally-safe pesticide. Houseplants that are noted for their roster of popular pests (aphids and white flies adore hibiscus) should be paid special attention. Remember to check under pot rims too. Sneaky scale insects and mealy bugs somehow know you are conducting an inspection and will try to gain entry to your home by stealth.
September is still time to repot houseplants before their winter stretch indoors. Plants remain active yet in the warm temperatures, and natural light is adequate to maintain new growth. Repotting is an exercise that places a certain amount of stress on plants. But at this time of year when growing conditions are favourable, re-potted specimens will be able to cope and recover long before all growth ceases later in December.
As natural light lessens so does plant growth, and so should your fertilizer schedule. Feed plants less often and taper off to plain water by the middle of December.
This autumn let your attention linger on the fall wild flowers that tend to be overlooked following a season of flamboyant cultivars. The simple beauty of native asters defines autumn in the country.

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