Tillington said: "Harry has left the buying group in great shape in 2015 having broken through the £200m barrier."
He was for many years managing director and shareholder of Findlay Clark Garden Centres in Scotland before their purchase by Dobbies. It was at this point that he took over as Tillington chairman.
The group recently held a dinner to mark the event in Latimer, Bucks, where he was presented with a reminder of his time with the group by Richard Webb, a founder member.
Squire's retirning managing director Dennis Espley is taking over as Tillington chairman.
Member Companies: Alton, Bents, Frosts, Hayes, Otter, Ruxley, Scotsdales, Squire’s, Van Hage, Webbs, Whitehall.