Urban Tree Concentrate

Fill the tree pit with a layer of 30 cm coarse gravel (100-150 mm grain size without fine particles) and compact it well with a road roller. Then apply the Stadtbaum concentrate mixed with quartz sand (ratio 1:4) in layers of 5 cm and flush it into the cavities of the coarse skeleton with a 3/4 inch water hose. Repeat this process until all cavities of the coarse skeleton are filled with the fine substrate mixture. Then apply the next layer of coarse gravel, compact it again, and rinse in this fine substrate mixture again. A tree pit created in this way should have a volume of 20-30 m³ and is completely buildable (i.e., with roads, sidewalks, etc.). All surface water in the surrounding area (including roof water) can be discharged into these pits. It is important to provide an overflow into the sewer. Each cubic meter of tree pit requires 250 liters (i.e., 25%) of this fine substrate mixture.

This product contains stably bound, climate-effective carbon. This carbon has already been certified and compensated for in the form of CO2 certificates. Therefore, it is not possible to sell such certificates for this product.

Planting trees is becoming increasingly important in cities, both to cool them down and to better control water levels. Especially when there is no separate sewer system, this innovative type of tree planting pays for itself within a few years through savings in sewerage costs. In addition, the trees grow vigorously and healthily and are much more resistant to increasingly severe weather events. There are practically no more failures after planting and the maintenance effort is significantly reduced. The first street in Austria to be constructed using this system in 2017 is Eggenberger Allee in Graz.

The challenge in substrate development was stability—after all, the tree should stand in this substrate for at least 100 years. Therefore, only stable and activated biochar and correspondingly stable quartz sand can be used as components.

For longer transport distances, we recommend using the concentrate instead of the Stadtbaum fine substrate product. Quartz sand is available locally in good quality almost everywhere, and for reasons of sustainability, it does not make sense to transport sand over long distances.

This concentrate was developed on behalf of the city of Graz and in collaboration with DI Erwin Murer to provide a durable substrate that is well suited for root growth between the coarse stones of the soil skeleton. It consists of our soil activator, which has been specially optimized for urban tree planting. On site, the concentrate must then be mixed with quartz sand in a ratio of 1:4.

Bulk density: 0.6 tons/m3