Kew Gardens has announced an opening date for its historic Temperate House, which has been closed while undergoing a five-year renovation.

The southwest London attraction said the Victorian glasshouse – the largest in the world – will reopen to the public on 5 May 2018, complete with 10,000 rare and exotic plants.

The long and painstaking restoration, designed by Donald Insall Associates and costing £41m (€46m, US$54m), is the biggest such project in Kew Gardens’ history, with the framework of the building, its intricate ironwork and ground paving carefully repaired and thousands of panes of glass replaced.

The Temperate House, which was designed by architect Decimus Burton and built in 1863, will be used for horticultural education and to showcase rare and sometimes near-extinct plant specimens. About 500 plants were housed in the glasshouse, which were removed and propagated by Kews’ gardeners throughout the restoration period. There are now 10,000 plants from all over the world being rehoused in the newly upgraded building, including Dombeya mauritiana, which was considered practically extinct until Kew horticulturalist Carlos Magdalena found one growing wild in Mauritius.

“A few weeks ago, I watched as some of the world's rarest plants were moved, with the utmost care, into the Temperate House. It was a seminal moment, kicking off the countdown to May's re-opening of what has to be Kew's most incredible building,” said director of horticulture Richard Barley.

"The Temperate House will be for everyone. From young to old, for budding gardeners or aspiring artists, for those making a pilgrimage from great distances, and for our local community, we hope every visitor will see plants in a new light."

The Heritage Lottery Fund awarded around £15m (US$19.6m, €16.8m) to the project, with £10m (US$13m, €11.2m) from the UK Department for Environment, Food & Rural Affairs, and £8m from private donations.

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