Urban tree fine substrate

Fill the tree pit with a 30 cm layer of coarse gravel (100-150 mm grain size without fine particles) and compact it well with a road roller. Then apply the fine substrate 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 fine substrate. Then apply the next layer of coarse gravel, compact it again, and flush in more fine substrate. 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 fine substrate.

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.

This substrate (formerly known as fine substrate skeletal soil) was developed on behalf of the city of Graz and in collaboration with DI Erwin Murer in order to provide a durable substrate that is easily penetrated by roots between the coarse stones of the soil skeleton. It consists of our Stadtbaum concentrate and quartz sand in a ratio of 1:4.

Bulk density: 1.25 tons/m3