Head of garden design Richard Wilford has themed the 320m Great Broad Walk Borders around Kew's science strategy, which is fundamental to the turnaround in the gardens' fortunes.
Stretching from the Orangery to the Palm House lake, the original borders by William Nesfield were all but lost. Nesfield's formal, intricate 1840s design along with the backbone provided by the original cedar avenue gave Wilford a starting point for the new design. Around 50 staff and volunteers spent four months planting the borders, which surprised everyone by flourishing in their first year, helped by a wet spring.
The new border peaks between June and September, with salvias dominating early on followed by rudbeckias and echinacea later in the season and achillea providing colour throughout the summer. A series of eight circles bisected by the wide pathway are each themed to a strand of Kew's science strategy. The first is filled with hybrids and cultivars such as Crocosmia 'Lucifer' and Gaura lindheimeri. The Lamiaceae (sage)-themed bed includes Perovskia, origanum, nepeta and 11 varieties of salvia. The sage family's chemical compounds form an important part of Kew's research.
The Asteraceae (daisy) family follows, representing just a few of the 500,000 dried Asteraceae specimens in the Kew herbarium and including the rare Symphyotrichum vahlii, an aster collected as seed in the Falkland Islands. Monocot-themed beds are filled with kniphofias, day lilies, crocosmias and grasses as well as 10 varieties of agapanthus. Other beds celebrate cultivars, plant life cycles, shade-tolerant species, pollination and seed dispersal. Topiary yews add formality and a sense of perspective, and spring bulbs will be planted in late summer this year to extend the season.
Throughout the beds are unobtrusive information panels linking the planting back to Kew's scientific work and listing all species used. Wilford explained: "Linking it to Kew's science is quite important. This is a fairly light touch in that sense but it gives an invitation that this isn't just a lovely border - it also has relevance to what Kew does."
Defra financed the £600,000 new resin-bound pathway and Mick and Barbara Davis, who are both members of the Kew Foundation, funded the borders themselves.
This is by far Wilford's biggest design. "It was quite daunting, but in a way I just forgot about what I was doing and concentrated on what I was drawing as a planting plan - not worrying about the fact that it's at Kew and it's going to be the biggest herbaceous border in the UK," he said.
"I had the luxury of having quite a lot of time. I had six months to sit down, do my research, visit other gardens and get my plant list together before I started drawing out the plans."
He cited the summery Sussex Prairie Garden, Piet Oudolf's new planting at Durslade Farm in Somerset, Wisley and various spots around Kew as inspiration for his final design. "I found plant combinations that I liked and nurseries like Orchard Dene had really good suggestions for plants that we could use in summer."
A few choice species were propagated from Kew's collections, including the Tennessee coneflower Echinacea tennesseensis, the South African Berkheya purpurea with its prickly rosette of leaves and the tiny Cotula fallax with its silvery foliage and yellow pom-pom flower heads.
But with Kew already growing 30,000 bedding plants each year it did not have the capacity to grow the total 30,000 needed for this project. Crocus won the competitive tendering process to supply most of the plants.
In future Kew can replenish most of the plants in the border through propagation, unless they have plant breeders rights, said Wilford. Three full-time staff will maintain the borders.
"Some things won't last as long as others and some of the grass I put in may not be the right ones - they're not tall enough," he added. "But we will have a much better idea next year when things are more mature."