Plant trees to create islands of coolness and water them well

Hot spells are going to happen again in the next few years and even become more frequent. That's why it's important to remember that, individually, we can do our part to make things better, even in small ways. And if we all do our part, it can only help.

This summer, in our greenhouses, it was very hot. We even had to close early one afternoon because it was unbearable. But outside it wasn't much better. What we all wanted was a little coolness. Most of us found ourselves in our air-conditioned homes, with the windows closed, without hearing the birds singing or feeling the breeze... 

It has been shown that it is cooler in areas where there is vegetation than in an area of buildings, concrete and without trees. The difference between a heat island and a cool island can be as much as 10 degrees.

"Trees have a very, very important impact at the local level. If you go 10 meters away, you don't feel it as much, but when you're really close to the trees, it's a direct impact," according to Virginie Angers, forestry engineer.

According to the report Mesures de luttes aux îlots de chaleur urbains of the Institut national de santé du Québec, " vegetation allows the creation of coolness through different processes, more precisely

- seasonal shading of infrastructure;
- evapotranspiration;
- minimization of ground temperature differences.

 Vegetation also offers other interesting and complementary benefits in urban environments, including:

- improved air quality through oxygen production, CO2 capture, filtration of airborne particles, and reduced energy demand for air conditioning;
- improved water quality through retention of rainwater in the soil and control of soil erosion;
- population health benefits, including protection from ultraviolet (UV) radiation, reduction of heat stress, and availability of places for physical activity. "

Trees to favor are those that provide the most shade and those that tend to spread horizontally, such as basswoods(Tilia), oaks(Quercus) and Norway maples(Acer platanoides), but for those with smaller yards, amur maples(Acer ginnala) and serviceberry(Amelanchier canadensis) are excellent choices. Norway maple produces a lot of samaras and can become invasive, so it's worth remembering. 

In our article on tree planting(here), we give tips for successful planting(soil, compost, mycorrhiza, etc.), even in the middle of summer. As you will read, the biggest part of your success is watering, because in the summer when it is very hot, trees, like us, need water.

Successful watering

In order to successfully water your tree after planting, it is important to consider three things: 1. gently; 2. long; 3. regularly.

1. Easy

Watering gently allows the water to penetrate deep into the soil and soak the roots. This is not the case with high flow watering, which tends to run off the surface rather than penetrate the soil. A tip: let a small stream of water run from your garden hose at the base of your tree for at least 30 minutes until it is saturated. 

2. Long time

This is probably the most important and most overlooked step for gardeners. A good way to become aware of how long we should be watering is to take the time to dig into the soil after our watering to see how deep the moisture is. It is quite surprising to find that most of the time the wet part is on the surface only! Watering deeply causes the root system of the plants to develop more deeply to draw water and, in doing so, the plants become more resistant to future droughts. 

3. Regularly

Regular watering always pays off in gardening, but one thing to remember is to let the soil dry before watering again. Gardeners often ask: how many times a week should I water? This is a difficult question to answer, as many factors can come into play, such as weather conditions and soil type. Remember that nothing will be more effective than putting your hands in the soil to see if you really need to water!

An absorbent that helps retain water

There is a product to help water retention in the soil: Super Ab Hydrogel granules, which reduces the frequency of watering by 50%. These potassium-based synthetic polymer granules absorb, retain and release over 200 times their weight in water. They also improve substrate aeration, reduce leaching of fertilizers and nutrients and allow for better cultivation on sloped surfaces.

Planting a tree today may not reduce the temperature in your backyard that much next summer, but it is important to think long-term. One mature tree can make a difference, several mature trees can have an even greater impact. According to some forecasts, average summer temperatures could rise by 3 to 5.8°C within 80 years. It is urgent to think today about the next generations, who will benefit from the actions taken now.