Tree register

A simple tree register provides information on the tree population, listing names and numbers. But the requirements for such a system go way beyond just providing information. With its large tree population, the City of Luxembourg has to maintain a full tree register. 

A tree's master data provides information on the following characteristics: Location, district, unique number and the person entering the data, plus tree species, crown diameter, trunk circumference, height and year of planting.

Road safety

With the introduction of the tree register, which helped make tree inspections more efficient and improved the monitoring of the number and condition of trees, the decision was also taken to apply the FLL tree inspection guidelines.

During tree inspections, any work that has to be undertaken is recorded for each tree under 'Maintenance' according to a list of measures and the measure is assigned a priority.

All maintenance measures and pending regular checks can be filtered by name, date and priority. These filter lists, showing pending work, are used for weekly planning with the maintenance teams.

Requirements for street trees

Street trees have the greatest potential for conflict and the greatest accumulation of stress factors. They are exposed to extreme heat and drought factors, and the sun's rays are also more intense, resulting in burns to the upper canopy.

Sealed surfaces, in particular, with their tarred and dark to black surfaces, cause additional problems for the undersides of leaves with their hot radiant heat.

Looking at historical pictures, you can see that on many streets and squares, the trees were taller than they are nowadays. This is due to roads' underground structure today. In the past, tree roots could reach further into the ground as there were fewer pipes and the soil was far less compacted. Even if this has have negative consequences, such as roots "invading" entire underground infrastructure lines, a requirement for all underground lines was introduced several decades ago which states that: Gas, water and sewage pipelines, as well as electricity, postal and internet connections, are laid in the ground.

Trees planted along roads, pavements and public squares are exposed to many negative influences, such as the water storage capacity of soils and their oxygen supply, road gritting, soil compaction and sealing, high pH values, vandalism, and damage caused by cars and construction machinery on building sites.

In the last ten years, however, it has gradually become accepted that tree pits should be enlarged underground (greater soil volume in terms of both width and depth), special substrates should be added that are conducive to root growth, and all necessary maintenance measures should be implemented, as explained in the following chapters.

Since 2005, the aim has been to increase the diversity of tree species in the city. Tree planting has been consistently planned for all existing and all new residential streets, as well as for green spaces, in order to continue increasing the number of trees.

The question of whether these species are native or non-native is less important in this regard.

Selecting tree varieties, since 2007

Starting in 2007, new tree genera were introduced into the tree population, initially in small numbers only, such as on new streets or during infrastructure works (gas, sewer and water pipelines) and on new roads.

Some examples