Brian Minter: Climate reality dictates a need for more heat and drought tolerant plants

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The drought and heat we’ve been experiencing this summer should motivate us all to reassess the viability of our current landscapes. Do we have the right plants for today’s climate realities?

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The recent weather pattern of excessive heat and longer periods without rain means we need more heat and drought tolerant plants in our gardens. For years, when choosing plants, we considered only cold tolerance for winter survival, but now heat tolerance must be part of the equation.

In urban areas, depending on a number of factors, the mean temperature is anywhere from two to four degrees Celsius warmer than the countryside. This is why urban forestry and the cooling effect of trees is becoming such a critical issue. If you don’t have air conditioning, and most people don’t, the right tree in the right place can be the equivalent of four air conditioners working eight hours a day.

Unfortunately, many trees have been planted in challenging locations. Many have also not been planted properly, and their roots cannot grow deep enough to make them more water self sufficient. When planting trees, the trick is to provide a deep planting hole, filled with quality soil, so a good root system can develop, and the roots can go deep and source their own water.

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It is also important to think about the rest of the inhabitants on this planet, including birds and other important wildlife. We are losing so many beneficial insects as it is, without the added stress of excessive heat. When we get temperatures close to 50C, bees, for example, are incapacitated. Even the heat we experienced in June caused serious issues for many beekeepers and their hives. Something as simple as cooling trees and shallow water in a bird bath can help birds, bees and other pollinators.

A carefully thought-out landscape, even in small space gardens, can provide critical habitat for a wide range of creatures. Many new tree varieties have a more narrow, columnar shape, which allows them to fit nicely into tighter spaces, but they can still grow eight to 12 feet wide and provide privacy, cooling and wildlife habitats.

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For hot, sunny areas, a more xeriscape approach is probably the way to go. By using very drought tolerant plants, like potentillas, spireas, gentians and sterile dwarf buddleias, you can still achieve excellent texture and colour, as well as ease of maintenance. Compact alpine evergreens, like some of the new low-growing pines, spruces and dwarf abies or true fir would also work. Many cedrus varieties originated in the deserts of the Middle East and have great drought tolerance. The diverse taxus (yew) families are quite tolerant of both heat and drought.

In the broadleaved family that is so popular on the west coast, small leaved varieties of both azaleas and rhododendrons are far more heat and drought tolerant than the large leaved species. Colourful euonymus, compact Japanese holly, laurels, leucothoe, nandinas, osmanthus, viburnums, and yuccas all offer unique beauty, as well as being more heat and drought tolerant.

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There is an ongoing love affair with hydrangeas, both the shade-loving macrophyllas and the sun-tolerant paniculatas. Many new mophead and lacecap varieties are not only more sun and heat tolerant but are also more compact and repeat flowering. The so-called mountain hydrangea, H. serrata, is native to the mountains of Asia and Japan. Tuff Stuff and Tuff Stuff Ah-Ha are two award-winning varieties that are incredibly tough and resilient. They are prime examples of a new generation of hydrangeas. The very hardy peegee types are also being bred to be more compact and more drought tolerant.

It’s no surprise that perennials seem to be, by far, the most resilient, and consequently, the most valuable plants in our landscapes. Summer heat lovers, like the rudbeckias I wrote about last week, coreopsis, heleniums and geraniums, like Rozanne, offer so much in the way of long, dependable colour and are a great source of pollen and nectar for our pollinators. In dry, shady areas, euphorbias, brunneras, hostas and Japanese anemones provide wonderful long-lasting colour with little maintenance once established.

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I’m thrilled to see the continued interest in ornamental grasses. They are the perfect garden plants of the future. This is their time to shine, and you really must look at the large number of remarkable new introductions that combine so well with other garden perennials, flowering shrubs and conifers in sun or shade. They are also the new stars in containers.

Finally, lawns. Most existing lawns were not planted properly. Playing fields and golf courses are planted in one foot of pure sand, allowing the roots to grow deep and over time turn that sand into rich organic matter. Once established in this situation, and using more drought tolerant grass varieties, lawns will stay greener with minimal watering. They will also cool our yards and neighbourhoods, be less of a fire hazard and will continue to produce oxygen and sequester carbon.

By rethinking our entire landscapes, we can do a far better job of cooling our homes and gardens, enjoy greater privacy and beauty, use far less water and provide much-needed habitat for wildlife. Climate change is a reality, and we need to be, in any way we can, part of the solution.