Why planting urban trees is so complicated – the "Spaghetti Subsurface Problem"

Cities need more greenery – but simply digging a hole and planting a tree, unfortunately, isn't that easy. Beneath our streets lies a dense, historically developed network of pipes for water, sewage, gas, electricity, and telecommunications. This Spaghetti Subsurface Problem makes every tree planting complicated: if the ground is opened, pipes must be located, secured, or rerouted – this is time-consuming and expensive. Additionally, historical cellars, old foundations, or geological conditions restrict the underground space.

Space quickly becomes tight beneath the street.

Tree roots need a lot of space, otherwise the tree will become sick and die. The underground infrastructure often gets in the way. Therefore, the ground often looks like a plate of spaghetti.

Another key point: Trees need root space. Over the long term, roots require at least as much space as the tree's future canopy. Without this space, the tree cannot grow healthily and often dies after just a few years. However, creating this essential root space is particularly challenging in dense urban areas. Conversely, care must be taken to ensure that tree roots do not damage existing infrastructure. Roots can wrap around pipes or penetrate sewage or water lines through fine cracks, causing damage.

Spaghetti-Subsurface on Mariahilfer Str. in Vienna (from Fetka 2020)

Above ground, space is also limited: In addition to space for traffic, gastronomy, and retail, areas must be reserved for temporary purposes such as the next city festival, the weekly market, or other events. Temporary thoroughfares remain necessary, and in heritage-protected areas, sightlines must not be obstructed by tree plantings. This also includes the tree's future canopy. This particularly applies to support cables stretched between buildings for trams or street lighting. The latter must be able to adequately illuminate streets or squares even after trees are planted.

Therefore, many stakeholders must be involved in every planting: civil engineering, parks department, utility providers, heritage conservation, public transport operators, fire department, traffic planning, residents, and businesses. Only after extensive planning and coordination can a tree be planted. Tree plantings therefore often cost between 10,000 and 40,000 Euros per tree when factoring in the total infrastructure costs. It becomes more cost-effective when tree plantings are part of measures where the entire underground infrastructure needs to be renewed anyway. However, this only occurs every 50 to 70 years.

This is where MobiGa systems offer a strong alternative.
They are quick to set up and immediately effective, thus creating more greenery in the short term without construction work. They are ideal as a temporary solution while planning and approval processes for actual tree plantings are underway. And they can be used permanently where planting is not possible at all due to spatial or technical reasons. If a MobiGa system ever gets in the way, it can be easily repositioned with a pallet jack. This makes urban greening feasible even where traditional city trees would fail.