Brian Minter: Climate change is forcing us to reconsider what we use for plant protection

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After our recent early introduction to winter, and considering the significant loss of many plants during last year’s long, cold January, we all need to reassess how we protect our more tender plants.

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As a result of global warming, climate change is proving to be a mixed bag of more severe conditions, from extreme heat and cold to atmospheric rivers and prolonged drought. Weather patterns are also skewed. Our seasons are changing and are no longer following typical calendar dates. It also seems that each season is setting new records for either heat or cold.

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Last week’s column about the Swiss landscape architects, Hope Strode and Federico De Molfetta, highlighted how forward-thinking designers are now using plants that will withstand these new climate realities.

We all need to take a fresh look at the plants we choose for our gardens in terms of heat and cold tolerance, and, as we move into early winter weather, the type of protection we give our more tender plants also needs to be re-evaluated.

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Today, many people love a tropical look in their gardens, and they are incorporating bananas, palms and some of the more resilient tender plants into their landscapes. However, to save those plants during more extreme winter conditions, we will need to adopt a more aggressive strategy for protection.

The very best way to ensure winter survival is to have a sheltered area where tender plants can simply be moved. Garages and patios which have some light and can be kept from freezing are ideal. Sometimes it’s easy to modify existing structures inexpensively to accomplish this, and I know many folks who do exactly that. Home greenhouses that will withstand winter snow loads are also excellent, but they will need to be protected from extreme cold, which means insulating and heating them will be necessary. Heating, however, can be costly.

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Sunroom additions to our homes are also becoming quite popular and work well for sheltering many tender plants, but larger, fast-growing plants, like bananas and palms, will always pose some problems.

Choosing to overwinter larger tender plants outdoors requires a good understanding of what it takes to succeed. Plant hardiness is a key factor. Not only do we need to know the cold tolerance of our plants, but we also need to understand the implications for the microclimates in which we live.

For example, in the eastern Fraser Valley, we are often exposed to very cold Arctic outflow winds. This can distort cold temperatures by many degrees if plants are in the direct path of these chilly winds. Creating wind breaks using evergreen trees and fences certainly helps, as does living near a forested area or in a tightly built housing community. As a matter of interest, our current zoning map, which includes both Canada and the U.S., is in the process of being revised.

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Elevation is also a factor. If you live on a mountainside, the higher up you are, generally the colder the temperatures are. Southern exposures are much less susceptible to cold winter winds. By selecting planting sites on the south or west side of your home, you will provide your plants with a more protected winter environment. If you add strategic hedging or windbreaks, you will also gain a few degrees of warmth.

The type of soil, too, makes a huge difference. Light, open, porous, well-draining soils help plants tolerate colder temperatures much better than heavy, wet, clay-based soils. As a rule, well-drained soils allow for deeper root penetration, which is helpful during both drought and cold situations.

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Once you feel comfortable rating your plants based on cold hardiness and heat zones and better understand your own microclimates, you will be able to make better plant choices for both summer and winter survival. To be fair, however, we all challenge these parameters by choosing trendy new plants that are not rated hardy for our planting zone. All good gardeners do this because we all want that special plant.

Container plants present the greatest concern. It’s important to know that, when plants are grown out of the ground, they lose at least one zone of hardiness. To protect them properly, depending of course on which plants are in the containers, we need to do a few things. During severe cold with temperatures below -10 to -20C, the containers should be moved into a protected area where the plants will only freeze lightly. At the very least, they need to be moved out of direct cold winds and into a secure area where the containers can be wrapped, plants and all, with a true protective cloth like N-Sulate which has a protective rating of ten degrees Celsius. They must also be kept moist before freezing to prevent desiccation of the foliage. These are crucial steps for all containers.

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Red banana plants (Ensete Maurelii) are tropical in nature and must be inside and kept warm. Green banana plants, like the semi-hardy Musa basjoo, must also be kept in a protected area that gets very little frost. In the garden, Musa basjoo bananas, once established for a year, can be cut to the ground and mulched with lots of fir or hemlock sawdust or bark mulch. It will sucker back up in the spring with many more new shoots. If you wish to keep the main stem alive, cut the leaves off and then put up a secure tripod around and over it. Mulch it and wrap it with N-Sulate cloth or bubble poly. If the weather gets severely cold, you need to wrap heat tape around the stem.

The same is true with other hardier plants, like a Dutch Windmill palm. Place a secure tripod of stakes around the plant, enclose the leaves inside and wrap the plant with N-Sulate, then with bubble poly. After last winter, I am also recommending heat tape around the stem.

All our other more tender garden plants should be mulched around the base with bark mulch and if exposed to the cold, outflow winter winds, wrapped with a protective covering, like N-Sulate,

In reality, although not yet according to our calendars, winter is here. Now is the time to protect our most cold-vulnerable plants. After so many losses last year, we need to be a little overprotective this year.