An RHS spokesperson said: "Nick Mattingley, RHS shows director is currently having to take some unexpected leave.
"Whilst he’s away the shows team are continuing as normal to plan the 2018 shows and are delighted with interest from exhibitors, designers, sponsors and growers wanting to be at Chelsea next year, which will be announced after the usual selection processes are completed."
Mattingley became RHS head of shows in 2015 and shows director in 2016. He previously worked in events and theatre for 25 years.
RHS shows development officer and Chelsea Show manager from 2015-17 Tom Harfleet announced he was leaving to join drinks company Seedlip last month. Katherine Potsides has taken over as Chelsea Show manager and the RHS is looking for a replacement for Harfleet.
Confirmations of show garden places are going out this week, with reports suggesting there are more applications than in 2017, when there were eight show gardens, half the number of the previous year.
A new 'new gardens spaces category' is replacing 'Fresh' gardens, with the HTA/Warnes McGarr and Robert Barker believed to be among applicants. Designers Jo Thompson and Sarah Price and sponsors M&G and Wedgwood are believed to be involved.