Stuart Medhurst, 54, siphoned off the funds to two accomplices while working at the RHS, the prosecution said. He is also accused of using his position at the RHS to buy £43,000 worth of goods for himself between 2007 and 2014. Medhurst appeared at Westminster Magistrates Court accused of two counts of conspiracy to steal and a charge of fraud by abuse of position.
He was in the dock alongside Shaheen Kadri, 43, of Camden, north London, and Elaine Summers, 53, of Notting Hill, west London, who are both charged with one count of conspiracy to steal.
It is alleged Kadri received £317,110 from Medhurst between January 2004 and January last year, and Summers took £360,859 over the same period.
Richard Doolan, prosecuting, said: "They are all charged with a conspiracy which relates to around £700,000 paid out of the RHS bank account."
He added: "Around £300,000 was paid out to a bank account controlled by Ms Summers and around another £300,000 was paid into an account controlled by Mr Kadri.
"The fraud relates to around £43,000 worth of goods that Mr Medhurst obtained while being a manager employed by the RHS."
All three defendants spoke only to confirm their identities during the hearing.
They were released on unconditional bail ahead of a preliminary hearing at Southwark Crown Court on 11 February. No pleas have yet been entered.
RHS director-general Sue Biggs said in a letter to staff: "Over the past three years we have been conducting in-depth audits across all our work and implementing more robust measures and controls to protect the society.
"Today we're in a much stronger and more robust position to ensure unacceptable activity could not take place within the society. As a charity, any losses to the revenue of the society will be covered by insurance.
"I want to assure you we routinely monitor our work and look at our procedures to safeguard the society."