Out with the old, in with the Kew

After a five-year restoration project, the Victorian Temperate House at Kew Gardens reopens this week as home to some of the world’s rarest plants
Kirsty O'Connor/PA Wire
Robert Bevan3 May 2018

Decimus Burton was a particularly innovative Victorian architect, so when he began building the Temperate House at Kew Gardens in 1860 he thought that pea-green tinted glass would create a healthier environment for the plants and trees gathered from as far afield as New Zealand and the Americas. He was utterly wrong. Within the first months of planting, the specimens began to die off. Clear greenhouse glass was swiftly substituted and used in the five interlinked octagonal and rectilinear glasshouses that he created over the following decades.

When the Grade I-listed Temperate House, the largest survivor of its type in the world, reopens after a five-year restoration project, the 10,000 plants of about 1,500 species, a significant portion of which were stored elsewhere during building works, are much more likely to thrive. Which is especially vital when you realise a few of the rarest species no longer exist in the wild. Seeds of other threatened plants have been germinated from Kew’s holdings at the Millennium Seedbank in Wakehurst in West Sussex. It will be a while before some of the giants reach the roof again and when they do the canopy will be less dense, with far more low-level vegetation. This means that in five to 10 years, visitors will be able to see exotic and unusual foliage at eye level instead of tall woody stems.

The £41million refurb, the first since those completed in the early 1980s, has been a mammoth undertaking for conservation architect Donald Insall Associates. In all, 69,000 elements, from massive trusses to nuts and bolts, have been taken down, repaired and reinstalled. A total of 15,000 panes of glass have been replaced under a scaffolding tent that could shelter three Boeing 747s. More than 100 urns around the edge of the roof have been craned off and fixed back, including the giant corner urns that Burton used to conceal the chimneys of the underground heating system. Now powered by a biomass plant, the Temperate House’s new controls will reduce Kew’s emissions by 20 per cent.

Given that various paint schemes have existed in different parts of the glasshouse over the centuries, the decision was made to repaint it in a unifying trio of creamy stone colours using fade-resistant oil-rig paint. The roof glazing follows the replacement pattern from the 1970s rather than trying to reinstall the ill-fitting wooden frames and opening sashes of the original. The steampunk iron rod and cog system previously used to hand winch the windows open has been supplemented by an automated system that can respond to changes in heat, wind speed and direction, creating a more even-tempered environment. Loos and a catering kitchenette have been installed, paths relaid, and rock gardens, pools and a waterfall set out within its 4,880 sq metres. Some of the structure has been strengthened so that aerial performances can take place.

Kew Gardens' Temperate House gets £41m facelift - In pictures

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For all its tremendous presence, though, the Temperate House is regarded as a less successful and original building than Burton’s smaller Palm House at Kew of 1844-48, a technological marvel that continues to inspire with its poetic merger of form and function. Earlier still, Burton had included conservatories in the Regency villas he designed, and in the 1830s he created the “Great Stove” at Chatsworth with the house’s head gardener, Joseph Paxton. This was a massive Palm House-like structure demolished after the First World War. Paxton, of course, went on to create his 1851 Crystal Palace.

Project architect Aimée Felton has had her life filled with the restoration of the Temperate House for the past few years. It would have been easier to take the entire building apart, she says: “The hardest thing was knowing when to stop. Dismantling the building would have helped us to get to some areas but it would have destroyed the charisma of the building and Burton’s legacy.” Instead the elements to be repaired or replaced were each tagged and given a grid reference and barcode so that they could be tracked by computer. Subjecting the almost complete restoration to an artificial rainstorm revealed leaks everywhere: “We couldn’t understand it,” says Felton. She then realised that they were putting everything back in perfect alignment when in fact the building had been built out of true with a great deal of craftsmanship, and this needed to be replicated.

A horticulturist waters plants the "Temperate House" at Kew Gardens
AFP/Getty Images

It will take years before the Temperate House is at its planted peak once more, but some plants that were too sensitive to move have had a head start. These were cocooned in situ for years while the building work went on around them. Some didn’t make it through the process, but among the survivors is the lonesome Wood’s Cycad from South Africa, which was already several hundred years old when it arrived at Kew in 1899. Only a handful of specimens survive worldwide, all male. The search for a female continues as the Cycad puts on new growth.

Richard Barley, Kew’s director of Horticulture, is excited to be able to display additional and more unusual occupants following the reopening of the Temperate House. There are now 2,000 more plants and double the variety of species. Among them is Dombeya mauritania, a species once thought to be extinct. The specimen has been grown from a cutting of a single plant found surviving on an island and now fluttering its heart-shaped red-and-green leaves. How tall will it grow? “I don’t know, I’ve never seen an older one,” says Barley.

The Temperate House, Barley says, “gives us an insight into what’s going on around the world. There is a lot still being discovered. That thing there,” he suggests, waving in the direction of the Australasian section, “might have the cure for cancer.”

The Temperate House, Kew Gardens (kew.org) opens to the public on Saturday

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