Mothering Sunday saw 160,000 blooms ordered in the new packaging, saving 50,000 litres of water. Overall 1.6m blooms should be sold in this way.
The change is thanks to Modified Atmosphere Packaging, a method similar to vacuum-packing, which keeps flowers fresher for longer.
The method removes oxygen, so carbon dioxide levels rise, slowing the respiration of the blooms.
M&S said it would need 19 fewer lorries to deliver Mother’s Day flowers this year.
The packaging is to be extended to all flowers sold in its stores by 2015.