Landscape designer Dan Pearson, who led the process, said extensive research has identified appropriate species and material that can cope with the conditions.
The team first headed to Deepdale Trees in Bedfordshire, one of two main suppliers in the planting process along with Palmstead Nurseries. Selected trees will spend two years at Deepdale prior to being planted on the bridge, grown in an exposed position in the nursery to acclimatize to the conditions over the Thames.
Pearson explained: "We inspected the first trees that are already in stock at the nursery, 'soft-tagging' the ones that fitted our specification of height and width. This is very important to the planting scheme, which has been carefully planned to frame beautiful views of London.
"Rootball size is also key to the success of the planting. The roots will act as anchor system forming an intertwining mesh in the soil to provide foundations for the vegetation. To enhance the root development further the plants will be potted up into the airpot system which stimulates a fibrous and balanced root system and hence good establishment."
"The ultimate element to selection is the character and the material for multi-stemmed trees which will flex in the wind and seamlessly blend with the naturalistic planting."
Following the Deepdale visit, the team headed to mainland Europe to spend two days meeting with experts from nurseries for advice and comparing and contrasting possible varieties to use.
"Some of the trees were selected for specific positions on the bridge and for their potential to become fully grown trees of up to 15m," Pearson said. "Over time these specimens will assume both character and help to provide certain locations with their own sense of place."
"Given the time of year it was a perfect time to assess the berry bearing trees that have been selected for autumn colour and for their foraging potential, which will help enhance wildlife as part of the ecology of the bridge.
"We hand-picked three different crab apple varieties, sorbus and hawthorns and a fine young apple tree with delicious fruit. Their spring blossom will be joined by a grove of Magnolia 'Merril' which is a white flowered form which was showing butter yellow foliage in the field. The vibrant colours used in the plant choices will attract pollinators enhancing biodiversity on the bridge and in neighbouring environments.
"The next round of work will be to match the soft-tagged trees to their positions on the plans and to fine tune the list before locking down the orders so that the trees can be brought back to the UK and the process begun of settling them in."