Planting trees in urban environments is a crucial step towards creating climate-adaptive and livable cities. Placing trees in tree boxes in city squares, shopping streets, parking lots, or city parks is a popular choice to create an aesthetic and characteristic cityscape. However, planting trees in tree boxes comes with various challenges. In this article, we will discuss these challenges and also look at an alternative approach: the use of bottomless tree boxes.
Limited Space for Root Growth
One of the most significant challenges of planting trees in tree boxes is the limited space for the roots to grow. Often, roots in tree boxes grow in circular patterns, also known as the ‘pot-bound’ effect. This can lead to root strangulation and reduced nutrient and water uptake. Moreover, the limited soil in a tree box can quickly become depleted of essential nutrients. As a result, the tree may show signs of stress, such as leaf yellowing, reduced growth, and even premature death. Additionally, a tree with limited root growth may be less stable and more likely to fall over in strong winds or storms.
Root Rot Lurking
Too little or too much water can have detrimental effects on the tree. When there is insufficient drainage, water can accumulate in the soil or in a tree box. This standing water enters the soil’s air pockets, preventing the tree roots from absorbing the oxygen they need to breathe. As a result, the roots can drown or suffocate, meaning they cannot effectively absorb water and nutrients to nourish the tree. So, even if there is plenty of water, the tree may actually suffer from a lack of water uptake due to the suffocated roots. It’s a paradoxical situation where too much water (due to poor drainage) can lead to symptoms similar to those of water shortage. To prevent this, a drainage hole is usually implemented in the tree box.
Tree boxes, especially those made from materials like metal or certain types of plastic, tend to heat up quickly when exposed to direct sunlight. This rapid warming can have harmful effects on the trees planted in them, such as root stress, water evaporation, and a reduction in growth rate. To minimize the negative effects of temperature fluctuations in tree boxes, it’s important to choose the right materials, water regularly, and, if possible, provide shade or insulation to the boxes during the hottest parts of the day.
Bottomless Tree Boxes: The Solution?
An interesting solution to minimize the challenges for trees in a tree box is the use of a bottomless tree box. Here, the tree is planted in the open ground, and the tree box serves as a decorative border around the tree. This brings several advantages:
- Natural root growth: Since the tree is planted in the open ground, the roots can spread naturally. Additionally, the tree has access to natural nutrients in the soil.
- Better water management: The natural soil provides better drainage and prevents water accumulation around the roots.
- Stable temperatures: The open ground offers natural insulation against temperature fluctuations.
Limited Underground Growth Space in the City
While a bottomless tree box brings crucial advantages, it doesn’t negate the fact that there is little underground growth space for trees in urban environments. When a tree is planted in the open ground instead of a tree box, the problem is shifted rather than actually solved. Therefore, in many cases – depending on the situation – we recommend providing the tree with additional rootable volume by using an underground tree bunker system. This creates an underground space in which tree roots can grow unhindered. While the tree gets the opportunity to grow old healthily in the urban environment, both the above-ground and underground infrastructure remain intact.
Moveable Tree Boxes for Events
We understand that it’s not always possible to place a bottomless tree box. Cities often buzz with events such as festivals and markets, making movable tree boxes sometimes necessary to accommodate them. Additionally, tree boxes are often used as road blockers during events. Although movable tree boxes can provide a solution in such situations, it means that the trees will likely not grow old and their potential will not be fully utilized.
Large Trees in a Charming City Square
Research by RIVM has shown that greenery reduces stress and can stimulate movement and social interaction. This has a positive effect on both mental and physical health. That’s why it’s all the more beautiful that a city square, where many events take place, is adorned with beautiful, large, and healthy trees. In the summer, they serve as natural parasols, preventing people from overheating during busy events, and in the winter, they can be decorated with countless lights to create a cozy and festive atmosphere. And we haven’t even mentioned the many climate benefits the trees will provide for the city throughout the year.
Go For Healthy Trees
Bottomless tree boxes offer a promising alternative for stylish urban planting. When trees are planted in a tree box with a bottom, they have insufficient space to develop into large, mature trees. It’s merely a temporary solution for urban greenery. To still enjoy the benefits of tree boxes – stylish, characteristic appearance in public spaces – we always recommend bottomless tree boxes if this option exists. This way, trees can be planted in the open ground, allowing the roots to grow naturally. However, we advise in many urban situations to also provide the tree with rootable volume underground by applying a tree bunker system.
By providing trees with the right growing conditions, we invest in a green, healthy urban environment in the long term!
Advice on Trees in Public Spaces
Want to transform a city or village square, shopping street, parking lot, or other public space into a future-proof and nature-inclusive environment? Make a no-obligation appointment with our experts for honest and professional advice on providing trees in public spaces with the right growing conditions.