They are being sent monthly parcels of flower, fruit and vegetable seeds, plants and bulbs and reporting on how they are growing, eventually helping produce a constantly updated map of mainland Britain showing what is growing where and when.
With Britain’s changing weather conditions the map will become an essential tool for gardeners and garden centres, enabling them to plan their activities more accurately, says Mr Fothergill's.
Sixteen gardeners are taking part and have already received their first parcel, which was broad beans, sweet peas and garlic.
Mr Fothergill's joint MD John Fothergill said: "We asked them to plant everything around the same date across the country so that we can monitor progress in the various areas. Members communicate online and via social media, giving regular updates on how the plants and seeds are performing. We will be able to see the true differences between autumn compared to spring planting as the members will be sent the same broad beans, sweet peas and garlic again in the spring.
Commercial director Tim Jeffries said: "Already we have seen fascinating differences from the group with different approaches to sowing sweet peas. This has prompted us to examine how seeds should be treated before sowing. What gets the best results; soaking, chipping, pouring on boiling water or just leaving it to nature?"