The Change.org petition, set up by London resident Julie Flanagan on Wednesday is addressed to the Secretaries of State for Environment, Food and Rural Affairs, Owen Paterson and Business, Innovation and Skills, Vince Cable, as well as the Chief Secretary to the Treasury Danny Alexander and Kew's local MP for Richmond Park Zac Goldsmith.
In it Flanagan says: "Never before has Kew faced such a significant threat to its future. It now needs your help to ensure its globally-important plant and fungal collections can continue to be used to support plant and fungal science and conservation around the world."
The west London institution revealed it had to tackle a £5m deficit at the end of last month, after Government funding has been slashed year-on-year over the life of the current Parliament.
Last week Kew director Richard Deverell told Horticulture Week that he has balanced the books for 2014/15 and will now ask for voluntary redundancies, reduced working hours, unpaid leave and compulsory redundancies.
Some 125 of Kew's 750 staff could go, with back office and scientific staff worst hit.
Ethnobotanist, television presenter and author James Wong, who trained at and worked at Kew, has been rallying support on social media site Twitter, using the hashtags #Time4Action and President Obama’s call to arms #YesWeCan.
He Tweeted yesterday: "One person every 33secs has signed the petition to save Kew Gardens from being dismantled. Halfway in 48hrs! #YesWeCan"
Wong told Horticulture Week that he was excited to see the numbers of signatures had trebled overnight from 2,000 to 6,000. People from across the world have signed, many leaving comments.
Laura Lagomarsino from Cambridge, USA, said: "Kew is the gold standard for botanical research and historical documentation. It is a resource to specialists and enthusiasts alike. It would be a tragedy to see this cut affect the science and outreach products from this institution."
Finn Rasmussen from Copenhagen, Denmark called Kew a pivotal institution in biology and plant science and the conservation of nature, adding: "Any further cuts would have detrimental effects for conservation efforts all over the globe."
York resident, Ellie Harrison pointed out: "I just heard Boris Johnson on the radio this week talking about how life sciences is a hugely important industry to the UK. So downsizing one of our most world renewed research institutions is how we celebrate this. Well done one and all."
Wong urged others to sign.
"I think it’s everyone’s duty to sign it. If you don’t know then fair enough but if you know anything about plants you know this is important. It takes only 30 seconds to do. It sounds dramatic but I believe you owe to the nation and to humanity.
"With 120 jobs going, that’s a massive and almost irreplaceable loss in knowledge. The amount of money we are talking about is nothing in the general scheme of things."
For more reaction to the cuts see next week’s issue of Horticulture Week.