Budding growers Joshua and Lily-Rose Bonney were delighted with their one, two finish in the annual primary schools' competition.
First placed Joshua took home a £50 book voucher whilst his sister netted £25.
Both pupils attend North Mundham Primary School, who received a total of £750 for their respective efforts.
The duo were among 1,600 children invited to grow a "pot 'mum" in the WSGA competition — now in its 13th year.
All entrants were given cuttings supplied by Yoder Toddington of Littlehampton, with compost and pots donated by Fargro.
The entrants were judged by a professional grower, and the winners were recognised for their good shape, blooms and buds.
WSGA chairman Dr Paul Sopp said: "The West Sussex Growers' Association is delighted with the quality of the plants that were grown. The idea behind the ‘pot 'mum' competition is to introduce young people to horticulture in the hope that some will pursue it as a serious interest or even a career. Unusually, both the winner, Joshua, and second-placed competitor, his sister Lily-Rose, came from the same school. They must come from a green-fingered family and we hope that they will provide inspiration for other young growers."
The awards were presented by WSGA member and leading chrysanthemum grower Colin Frampton of Donaldsons in Chichester.
Third prize went to Owen White of Elm Grove Primary School in Littlehampton.
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