Trees and mental health: what science says, and what your garden can change
A study conducted in Toronto revealed something astonishing: having ten more trees in your block improves your perception of your own health as much as feeling seven years younger. The figure is striking — but it raises a question. You do not choose the trees on your street. However, you do choose those in your garden. And this is precisely where this science becomes tangible.
What science really shows
The link between the presence of trees and psychological well-being is no longer an intuition: it is a solid field of research.
The Toronto study, published inScientific Reportsin 2015 by Omid Kardan and his colleagues, combined satellite imagery, the city's tree inventory, and health reports from tens of thousands of residents. The result: people living on more densely treed streets report better perceived health and fewer cardio-metabolic disorders — at equivalent income and social status levels.
Other studies point in the same direction. Research on "forest bathing" shows a measurable decrease in physiological stress after time spent among trees. Conversely, as researchers from the University of Bordeaux remind us, a lack of green spaces is associated with more instances of psychological distress — anxiety, depression.
Let’s be clear: a garden is not a treatment. When facing a real psychological difficulty, nothing replaces appropriate support. However, there is now enough evidence for researchers to consider daily contact with plants as a genuine lever for well-being — and public health.
The 3-30-300 rule — and why it starts with you
In 2021, researcher Cecil Konijnendijk proposed a simple rule to measure sufficient access to nature in the city: the rule3-30-300.
It consists of three numbers: seeing at least3 treesfrom your home, living in a neighbourhood covered by30 %canopy, and residing less than300 metresfrom a green space. A study conducted in Barcelona in 2022 found that residents whose homes approached this rule consumed fewer medications and consulted a psychologist or psychiatrist less often. In Wallonia, the IWEPS has also applied this framework to assess access to wooded areas for Walloons.
Of these three criteria, two depend on the city and urban planning. But the first — seeing three trees from your home — largely depends on you. It’s your garden, your window view, your terrace.
Brussels is green — but your garden matters more than you think
Brussels has a reputation as a green capital, and it is well-deserved: nearly half of its territory is covered in vegetation, and the Region counts around 90,000 trees across 167 species. However, this wealth is unevenly distributed — access to trees varies greatly from one neighbourhood to another.
And there is a figure that is rarely mentioned: privategardens cover about 22% of the regional territory— which is more than all the accessible public parks and green spaces, around 18%. In other words, private gardens are not a detail in the Brussels landscape: taken together, theyarea major part of the city's green infrastructure.
Your garden therefore counts twice. On the scale of the city, as a link in this green network. And on your scale, because it is the natural space with which you have the most daily contact — the one you see from the kitchen, where you have your coffee, where you unwind at the end of the day.
Designing a garden that truly does good
Not all gardens are equal in this regard. A garden that truly supports well-being is not just a pretty garden — it is a garden designed for that.
This means one or moretrees visible from the inside— the rule of '3 trees', scaled down to the size of the house. Places to bein the green, and not just to look at it: a bench, a terrace surrounded by plants. A dans le vert, et pas seulement le regarder : un banc, une terrasse entourée de plantations. Une presence in all seasons, so that the garden offers something even in winter. And — a point often forgotten — a garden whosemaintenance does not itself become a source of stress: a restful space should not turn into a permanent chore.
This is exactly what we think about at Vert Val when designing a residential garden in Brabant Wallon or Brussels: an outdoor space that is beautiful, yes, but also a place that genuinely benefits those who inhabit it, day after day.
Frequently Asked Questions
Do trees really have an effect on mental health?
Yes — this is a well-documented link today. Several studies associate proximity to trees and green spaces with lower stress, better mood, and less psychological distress. It is a factor of well-being, not a medical treatment, but the effect is well established enough for researchers to discuss it as a public health lever.
What is the 3-30-300 rule?
It is a benchmark proposed in 2021 by researcher Cecil Konijnendijk: seeing at least 3 trees from your home, living in a neighbourhood with 30% tree cover, and residing less than 300 metres from a green space. A 2022 study in Barcelona linked adherence to this rule with better well-being among residents.
Do you need a large garden to benefit from it?
No. The benefit mainly comes from daily contact with greenery, not from the size. A small city garden, a courtyard, or even a well-planted terrace, with a tree visible from inside, is enough to make a real difference.
What trees should be planted in a small garden?
Small-growing trees, suited to your soil and exposure: serviceberry, Japanese maple, Judas tree, birch, or ornamental apple are reliable choices. The right choice always depends on the location — this is one of the points where the advice of a landscape architect is useful.
In summary
The science is clear: living near trees is beneficial, and it's not just a matter of public parks. The garden you see every day is, on your scale, the most direct lever. Well thought out, it becomes much more than a backdrop: a place that supports, discreetly and sustainably, your well-being.
