The tallest sunflower stands 318cm high and has 11 heads.
The Russian Giant sunflowers were grown from seeds distributed free with copies of Nursery World in March for the Sunflower Challenge.
Nursery manager Sian Pugh said the children had enjoyed watering the sunflowers and watching them grow. 'Planting the seeds in the soil was a very tactile activity,' she said. 'The sunflowers have got so tall - when the weather improved they just went manic.'
The nursery plans to reward those who have grown the tallest plants with book prizes, and the children will use seeds from their sunflowers' heads to make thank-you cards for everyone who has sponsored them.
The Sunflower Challenge is organised by the National Day Nurseries Association and the charity WaterAid, and supported by Nursery World.
The sunflowers were sponsored to raise funds for the provision of safe drinking water for children in Malawi in southern Africa.
Mallards Wood, along with other nurseries across the UK, will take final height measurements in September to determine who has grown the tallest sunflower.
