Current Limagrain head of corporate finance Cecile Cuzenic will move to Suttons on 7 September to shadow Grenfell.
Cuzenic has been at Limagrain since 1989. Mike Yoxon moves up to take Cuzenic's role.
Grenfell joined Suttons in 1988 as finance director and became managing director in 1990.
Suttons Consumer Products was put up for sale by parent firm Vilmorin in 2007 but was recently taken off the market. Vilmorin has owned Suttons since 1993. It sold its German operations in 2008.
In the year ending June 2008, Suttons Consumer Products posted £500,000 profits on sales of £17m. Grenfell says that this will improve this year.
Meanwhile, Mr Fothergill's has taken over Suttons' main seed account at Homebase.
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