Temperatures are reaching records for the end of September, Normandy is no exception with 28°C in Caen and 27°C in Rouen – as much as in Verona in Northern Italy. In the gardens, how do trees and shrubs react to this Indian summer?
Normandy trees aren’t doing so badly. And that’s good news. Let’s say that it’s not the summer weather that will affect them. “What can weaken trees is the accumulation of events: late and intense frosts, several summers that are too dry and very hot…all of this will make them more susceptible to diseases.” believes Jean-Loup Charpentier. He is a biologist, ecologist and runs a Nordic Rustic nursery.
He conducts tests by planting unusual species under Norman skies and mixing them. Yuzu, or a variety of mandarin from Japan, adapts well to the land of Eure. Its focus of work: resistance to cold and water stress.
a Satsuma mandarin, a variety native to the Japanese mountains, which grows very well in Eure • © JL Charpentier
“Several scenarios are possible in terms of climate change. We would tend towards hotter and drier summers, and more violent climatic episodes such as late frost and heavy precipitation. You must therefore be careful about the species and varieties you buy..” Jean-Loup Charpentier recommends diversifying fruit trees in gardens, by mixing apple trees, pear trees and plum trees.
According to him, the pomegranate tree (resistant to cold and dry), olive trees and vines have a future in Normandy. Like citrus fruits. “It is also important not to buy your trees just anywhere. In some large garden centers, salespeople cannot know everything about their plants. However, determining the rootstock is important information for knowing resistance to disease or frost.”
Let’s return to our Indian summer: a fruit tree like the Norman apple tree should not suffer from these high temperatures at the end of the season, while beeches and oaks are more sensitive to drought. “Fortunately it rained in August, it saved the trees and the vegetation, and it avoided damage, but in the South this year, it is violent for the trees” specifies Jean-Loup Charpentier.
Knowing the nature of the soil, identifying the driest areas of the garden and those subject to cold winds in winter, allows you to choose the most suitable varieties • © JL Charpentier
At a nursery in Clinchamps-sur-Orne south of Caen, the 2,400 m2 of shrubs and plants are watered with rainwater. For Philippe Reussard, at the head of the company for 17 years, ““It’s not the first time we’ve been hot at the end of September, and we’re on schedule in terms of the life cycle of the trees.”
So don’t worry if the well-stocked foliage doesn’t seem ready to enter autumn. Some trees even bud again.
With the heat, the trees start growing again, it’s common to see this in September.
Philippe Reussard, nurseryman
“September is often a month of growth for trees. What causes their leaves to fall is the temperature delta between day and night.” he explains. It takes a significant difference between daytime and nighttime temperatures for trees to shift into fall mode and stop photosynthesis.
As for precipitation, his readings don’t worry him: “Normally around 700 millimeters of water falls per year, currently we are at 580-600 mm. If it rains this fall, we will have a classic year.”
Watering your plants and trees with rainwater is what the Clinchamps sur Orne nurseryman recommends • © Couleurs jardin
Philippe Reussard insists on one thing for private gardens as well as for communities: “we must respect the water cycle.” This means for him to do everything so that the rainwater returns to the earth.
“There is nothing more ecological than watering. On the condition that it is carried out with gray water, rainwater. And not with water treated industrially to make it suitable for consumption. It is absurd to water with drinking water. We should also rethink the system for discharging gray water from wastewater treatment plants: instead of going into the river, it should be used for other uses that allow a return to the earth. Such as watering or cleaning roads.”.
To your rainwater collection containers! On the condition that the overflow does not go back to the pipes, but to your garden.
In the heat of late summer, the nurseryman concludes with a bit of wisdom: “what can we do about it? When we work with nature, we adapt, and it adapts, too.”
How do trees lose their leaves in the fall?
The leaves are equipped with sensors that detect the shortening of the days. These sensors send a message to the trees which cause the creation of sort of plugs at the entrance to each leaf. These are no longer supplied with sap. Photosynthesis which takes place in the leaves is stopped; chlorophyll degrades and the foliage then changes from green to golden, red or brown hues. Before falling.
During the summer, some trees shed their leaves. This may be a process of protecting trees which thus attempt to conserve water resources.
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