The charity is believed to want one overarching banner that will bring together all of its activities, including the Chelsea and Hampton Court flower shows.
East London-based marketing agency Creature won the business following a competitive pitch run by Agency Insight. The company has worked for the Green Party, Bernard Matthews turkeys and the Environmental Justice Foundation.
The RHS is believed to be planning to spend around £1m to £1.5m on the campaign to buy media space and create the work.
Creature said: "We're a place where creative people come together to make amazing things, whether those things end up being TV ads, posters, websites, apps or whatever."
Arthur London has worked with the charity from December last year. Material Works and M&C Saatchi have also done some work for the organisation previously.
Creature’s managing partner Dan Shute said: "Having wholeheartedly embraced gardening puns left, right and centre throughout the pitch process, it would be remiss of me not to say that the seeds of something pretty special have been sown over the last few weeks, and we can’t wait to roll our sleeves up and get our hands dirty with the good folk at the RHS."
RHS 2015/16 accounts show membership rose 20,000 to 448,977 while income was up 4.7 per cent to £76.5m. Expenditure was up 8.3 per cent to £71.1m. Members and marketing spend was £18.3m, some 24 per cent of expenditure.
Tom Shelston, the director of members and marketing at the RHS, said: "The RHS wants to enrich everyone’s life through plants, and make the UK a greener and more beautiful place. Over the next ten years, we’re making a landmark £160 million investment in the future of horticulture to help realise this vision and we’re delighted that Creature will be helping us to tell that story."