The legacy of a father and son who transformed the botanical gardens in Kew into a worldwide attraction has been officially recognised.

Sir William Hooker and his son Sir Joseph were two of the first directors at Kew Gardens.

Their contribution towards botanical study was commemorated on Tuesday when Princess Alexandra unveiled an English Heritage blue plaque at their former home on Kew Green.

She chatted to staff before the ceremony, which was attended by descendants of the Hooker family as well as two former directors at Kew.

Kew’s current director, Stephen Hopper, who lives in the house on Kew Green, recalled how he had been inspired as a child growing up in west Tasmania, Australia, by the work of the Hookers.

He said: “Never in my wildest dreams did I think I would be standing here commemorating their wonderful contribution to science.”

He paid tribute to the two scientists, whose pioneering work had an enormous influence on the scientific study of plants and the continued success of Kew.

Sir William was appointed director of the newly nationalised botanic gardens in 1841.

The gardens had fallen into neglect following the death of Sir Joseph Banks in 1820.

During his 24 years as director, Sir William transformed the gardens in size and scale and also opened them to the public.

In 1841, the first year the gardens opened to the public, 9,000 people visited. By 1865 the number of visitors had risen to 500,000.

Prof Hopper said: “I have a small map of Kew which shows the 11 acres Sir William inherited when he was the first director.

“Within five years Kew was 250 acres in extent.

“The Palm House had been founded and the Museum No 1 had been founded and Kew, more or less as we experience it today, had been worked out.”

Sir William’s son was made assistant director in 1855.

Following his father’s death in 1865 he succeeded him as director.

Before taking over at Kew, Sir Joseph travelled aboard HMS Erebus, cataloguing the plants he observed.

On his return he was asked to classify the plants Charles Darwin had collected in the Galapagos islands.

During his tenure at Kew, Sir Joseph continued his father’s vision to transform the gardens into the attraction it is today.

He did, however, come into conflict with the public over access to Kew.

Protests were held in Kew Road with people calling for the gardens to be opened all day. Sir Joseph resisted saying Kew was for “serious scientific study”.

He was also responsible for raising the boundary wall, which still stands today, by 3ft.

He died in 1911. The house where he and his father lived has since been home to 13 directors and their families.

Mayor of Richmond, Councillor David Marlow, who attended the event, said he was delighted the father and son team had been honoured.

“It is a jewel in the borough and without these two it might not have been here.”

The Hookers were nominated for a blue plaque by Janet O’Connor and Alan Hart.

The scheme has been running 140 years and there are now more than 800 plaques in London.