The project involved extending a landscaped park between a group of residential buildings in Asnières.
• Client: The City of Asnières-sur-Seine
• Developer of the new district: CITALLIOS
• Landscape architect - Project manager: Agence TER
• Landscape architect - Project managers for planting the five sequoias: LAND'ACT Paysagistes: https://land-act.fr/
• The tree nursery : LACHAUX Paysage
Extension and development of a landscaped park in Asnières
The city launched a project management call for tenders, which was awarded by TER. Industrial buildings were demolished and the land was decontaminated. The existing park doubled in size from 1 to 2 hectares. The park contained twenty very large poplars (21 metres tall), ten of which were in poor health and posed a danger to local residents. The municipality therefore instructed TER to cut down the ten dangerous trees, but the company in charge of the slaughter mistakenly destroyed the ten healthy trees instead. Ultimately, all 20 poplars were cut down, sparking discontent among local residents who missed the beautiful view of these large trees. Asnières then decided to replant five large trees, hiring Land'Act to carry out the work.
'As a tree enthusiast, the mayor of Asnières chose Sequoia sempervirens because they can withstand dry urban environments and poor soil quality,' explains Christophe Jegaden of Land'Act. He adds, 'This has nothing to do with the sequoias in the national parks of the American West.'
Planting 5 large sequoias
The process of planting five large sequoias began six months before the trees were planted. Mr Jegaden went into detail about the various services his company would perform: pruning and selecting plants, planting and watering. He then prepared the technical specifications for planting (CCTP), including technical documentation, documents, cross-sections, diagrams, etc..
He explains, 'The trees were selected in a nursery, then marked and reserved.' The next issue to address was how to transport and lift the trees, which were 15 meters tall and weighed no less than five tons. Their root balls measured 2.4 meters in diameter and 1 meter in height. Each tree was transported by truck and required a crane for lifting. 'Five pits, each measuring 5 x 5 meters and 1.5 meters deep, were dug. We lifted the trees and placed them in the pits,' C. Jegaden continues. The root balls were placed at the bottom of the pits on a mixture of soil and stones that constitutes the bearing layer. They were then backfilled with special soil. Finally, the trees were equipped with a large staking system measuring 4 m x 4 m.
Four different types of watering systems to promote tree rooting
Before planting, a standard BIO5 Lite-Net retaining net was placed around each root ball. 'It works a bit like sock, allowing water to enter the pores of the product and be stored,' Christophe explains. This system 100% biodegradable in five years, maintains the humidity of the root ball fostering the root regrowth of the tree. LITE-SOIL, distributed in France by Urbaouest, offers water retention and underground irrigation solutions that save up to 70% water and reduce watering frequency by a factor of 3
Before planting, a standard BIO5 Lite-Net retaining net was placed around each root ball
Lite-Strip water retainers, resembling small wicks butts, were added to this system and scattered in the soil around the root ball. 'This improves the substrate and stores water near the roots, which contributes to the tree's recovery,' explains Mr Jegaden. Drains were installed at the bottom of each root ball to allow excess water to drain away. 10 liters of lite-strip can store 9 liters of water, 9 times the water retention capacity of clay beads.
On the surface above the root balls, a third irrigation system was installed: a drip irrigation system such as Rain Bird XFD or Netafim Technet. Finally, a misting system was added: a 25 mm HDPE irrigation hose with five misting sprinklers at the top was fitted to the trunk of each sequoia. Indeed, in order for the sequoia to properly take root, its foliage must remain constantly moist. The system is turned on three times a day for five to ten minutes and the drip irrigation is activated regularly.
Over the first four months, 500 ml of water were used per week. Christophe Jegaden concludes: 'The planting took place in October and we can say that it is a success. The trees are well rooted, and their growth has resumed."
