Zoöp Observations: Young Trees of Heaven
4 September 2023
The New Garden fetures two trees of heaven of roughly the same age (30 years) as the building of the New Institute. For the construction of what was then called the Netherlands Architecture Institute several large trees had to be felled. To quickly restore the green canopy to the area after its completion in 1993, two trees of heaven were planted. The tree of heaven (Ailanthus altissima) is a very fast grower that can easily reach a height of 10 meters within a few years, with up to 25 meters at a somewhat slower pace. Initially, these two trees looked out on a bare green lawn. Since this lawn gave way to the New Garden (2015), the undergrowth has become considerably more varied and rugged.
The tree of heaven is a dioecious species, meaning that there are male and female trees. If trees of both sexes are in close proximity to each other, pollination by insects can occur. Female trees set fruit, causing the species to spread. Because trees of heaven produce a lot of seeds, they can also produce a lot of seedlings. A mother tree can also form sprouts from root buds over great distances. Since 2019, the tree of heaven has been designated as an invasive exotic species by the European Union. EU member states are obligated to locate and destroy or control the populations present. New plantings are prohibited. The two trees of heaven in the New Garden are marked on a distribution map of the municipality of Rotterdam. Both are female trees with sterile stamens, meaning that they can only reproduce through root sprouts. Until 2015 that wasn't an issue: because the lawn was mowed very regularly, all sprouts were automatically destroyed. However, in the New Garden these sprouts have indeed become a problem, albeit one that is reasonably manageable. Today I counted five shoots that have grown so considerably this season that they now tower over the surrounding vegetation. In doing so they signed their own death warrant.
Artist Frank Bruggeman, in collaboration with researcher and author Peter Zwaal, describes what he sees happening in The New Garden since spring 2022, when the Nieuwe Instituut officially became a zoop.
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