Choosing planting

My bush is losing its leaves in summer: why?

better understand this phenomenon, its consequences, and the solutions

Contents

Modified the 7 December 2025 by Ingrid 3 min. Spring, Summer Difficulty: Débutant

In the height of summer, you may notice that some of your bushes are losing their leaves abnormally, or that the foliage is turning yellow and dry? While this phenomenon is quite normal in autumn, especially among deciduous bushes, it can indeed seem concerning at this time of year. Some tree tops and climbers also appear to be affected. The heat, drought, and repeated heatwaves are the main causes. We explain why your bush is losing its leaves in summer and what can be done to help it.

Some leaves of this young magnolia have dried out in the height of summer due to lack of water and the heatwave

Spring, Summer Difficulty

Drought, the main cause

Since recent years, drought and heatwaves have become increasingly frequent. While a gardener’s instinct is to seek shade and coolness during intense heat, the bush has no choice but to remain in the ground, suffering greatly, especially from lack of water. However, plants have developed strategies to try to survive.

A Survival Reflex

Did you know that bushes transpire through their leaves? Therefore, when bushes lack water, they try to transpire less to conserve their reserves. They then close their stomata, those microscopic pores on the leaves that allow for the plant’s evapotranspiration and gas exchanges (such as CO2 uptake, etc.). However, the leaf can no longer transpire to lower its temperature in the heat and may then scorch in the sun. The pigments in the leaf will degrade and change colour, much like in autumn.

The bush may also decide to stop supplying sap to the tips of its branches and thus its leaves. This results in a rapid loss of foliage. This phenomenon allows the bush to slow down its functioning and halt its growth to conserve its water reserves and energy. The plant voluntarily sacrifices its leaves to ensure its survival, waiting for rain or watering. This “defoliation” is particularly noticeable in the cymes of large specimens or trees in summer.

falling leaf

The consequences on the bush

This water stress, caused by drought, will have varying consequences on the bush depending on its duration and intensity.

Firstly, the bush may stop its growth for this season and will only resume growth the following spring.
If the drought is prolonged, it will have to draw on its water and energy reserves, normally intended for winter. It may therefore be less resistant to cold in winter and more susceptible to diseases.
The bush may lose only a few leaves to several branches depending on the duration of the drought in mid-summer. It will sacrifice its leaves and branches in an attempt to protect its buds and root system. If its buds and roots are affected, the bush is very likely to decline.
If it is a deciduous bush, it often loses its leaves earlier than usual in autumn to conserve its already depleted reserves from summer.

dead leaf in summer

What can I do to help my bush?

Firstly, water your bushes regularly and abundantly with rainwater, late in the evening or early in the morning, during heatwaves and prolonged droughts. Avoid watering between 8am and 8pm and do not wet the foliage.
If your bush is young, be especially vigilant during the first two summers!
Apply an organic mulch at the base of your bush to keep its roots cool and limit water evaporation.
Remove partially damaged leaves to further reduce transpiration, then also remove dead leaves and prune the dry branches.

Watering

Other possible causes

A young bush

A young bush, whose root system is still underdeveloped, will be more sensitive to drought than an older specimen. Generally, it is said that it takes 2 years for a plant to be sufficiently well-rooted. Once again, lack of water is often to blame.

Planting against a white wall

Planting bushes or perennials against a building facade or a white wall can lead to burns on the leaves. Indeed, the reflection of sunlight on this surface causes what resembles “sunburn” on the leaves. Again, soil dryness can be an aggravating factor.