William Notcutt is to leave Notcutts at the end of November to set up an agriculture and forestry business.
He will resign as deputy chairman of the Notcutts board, ending the family's direct day-to-day involvement at the fourth-generation family-owned group, which was founded as a nursery in 1897.
He said that "personal changes and the opportunity to make the change" prompted the move, adding: "My sister Caroline will remain as a non-executive director, otherwise it is the end of direct family involvement in Notcutts."
Former Body Shop global marketing director Andy King now runs the Norwich-based 19 garden centre group, which sold its nursery business to managers including John Lord in 2007.
Notcutts closed its landscape business in 2008, with Deakin Lock taking over some parts, and bought six NWF centres that year for £14.5m. Notcutt's father Charles remains president.
William Notcutt added: "We've had a singular focus on garden centres as opposed to a broader focus on traditional nursery, landscape, forestry and agriculture for some time."
William Notcutt Estates will now manage former Notcutts' forests and farmland. William will remain a shareholder of Notcutts and will provide some consultancy services to the company, but will cease to be an employee and director.
William Notcutt CV
1993: Joined Notcutts nursery as a management trainee
1999-07: Group/landscape managing director
2003-2005: Nursery managing director
2007-2011: Deputy chairman