Tips to keep your plants alive in scorching summer heat

Help plants survive the heat

It’s official, the world recorded the hottest day ever on July 4, with experts expecting that record to fall shortly, as high temperatures continue.

These high temperatures are not just hard on people and pets. They’re also tough on plants, even the plants the Okanagan Xeriscape Association recommends as appropriate for our semi-arid climate with its hot summer weather.

Many gardeners are familiar with the basic steps to ensure their plants can survive when the temperature is scorching, such as watering deeply but infrequently and applying a layer of organic mulch to conserve soil moisture.

Many may not be as familiar with what to avoid doing to their plants in times of extreme heat.

For instance, do not prune your plants in the heat.

Periods of intense heat are stressful for your plants, and pruning, especially thinning, will only serve to increase this stress.

Removing leaf matter will only increase the effects of heat on the remaining vegetation, decreasing the humidity and therefore forcing the remaining leaves to transpire more to cool the plant.

This often has disastrous results.

Another no-no in periods of extreme heat is fertilizing your plants.

Try to make sure your garden has the nutrients necessary for plant health prior to any spike in temperature.

Adding fertilizer is almost akin to adding salt to your soil as fertilizer essentially makes it harder for your plants to access the water in the soil.

High concentrations of nutrients actually reverse osmosis, the process by which a plant is able to absorb water from the soil.

The osmotic pressure is reversed so that the pressure outside the roots becomes greater than inside, making plants unable to access moisture from the soil and they actually lose water back into the surrounding ground.

Out of necessity the landscape industry must continue to plant throughout the hottest summer weather but this is far from an ideal situation.

If at all possible delay your planting to the coolness of shorter days in late summer when the ambient air temperature has decreased but the warm soil necessary for strong root establishment exists.

If you must plant in high heat, at least offer supplemental shade for new plantings by using shade cloth or, in a pinch, an old white sheet.

This shade is even more vital if you are planting in an area of ‘high albedo.’

High albedo environments occur where there is a great deal of reflection such as found in a rock garden.

This reflective sunlight will damage young plants that can not transpire enough in the high heat to cool their leaves and almost immediately begin exhibiting heat stress.

This can occur amazingly quickly as I witnessed recently when visiting a friend in Vernon and watched landscapers install young maples in a sea of rock in 35 C heat.

Two days later the maples were already dying and I doubt any of the six expensive young trees will survive the summer. It was very sad.

I guess it’s built-in job security for the landscapers though, as they will no doubt return in the months to come to haul away the dead trees and replant.

I was in Vernon to provide educational outreach for the Okanagan WaterWise Make Water Work campaign at both Nicholas Alexander and Swan Lake nurseries. Both partners are enthusiastically educating the gardening public on plant choices better-suited for our semi-arid environment.

Why not visit makewaterwork.ca and take the pledge to use water more efficiently on your landscape, and become eligible to win one of two $500 gift certificates?

OXA’s UnH2O Xeriscape Demonstration Garden at 4075 Gordon Dr. is looking spectacular right now, so stop in and see first-hand the beauty, resilience, and sustainability that is xeriscape.

The Okanagan Xeriscape Association is extremely grateful for the ongoing financial support of the Okanagan Basin Water Board and is proud to be collaborating with them on their Make Water Work campaign.

Sigrie Kendrick is a Master Gardener and executive director of the Okanagan Xeriscape Association and can be reached at 778-363-8360 or by email at [email protected].

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.

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About the Author

I inherited my passion for gardening from my Australian grandfather, a renowned rose breeder in New South Wales. My interest in water conservation started early after a childhood spent growing up in the desert of Saudi Arabia, when a day of rain was cause for a national holiday.

After meeting Gwen Steele, co-founder of the OXA through the master gardener program, I became passionate about promoting xeriscape. I joined the OXA board as a director in 2015 and became executive director in 2019.

When not promoting the principles of xeriscape and gardening for clients throughout the valley, I can be found on a rural property outside of Kelowna where I harvest thousands of litres of rainwater with which to water my own xeriscape gardens.

Connect with me at [email protected].

Visit the website at: www.okanaganxeriscape.org


The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet does not warrant the contents.

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