Waitrose sales fell 0.6 per cent in the week to February 14, although Valentine's Day proved popular, with the supermarket revealing flower sales jumped 19 per cent on last year.
A £29.50 'upper class' bouquet was a top seller.
The figures come in the week Horticulture Week revealed Waitrose has decided against sponsoring the NFU UK Horticulture exhibit for a fourth year in succession at RHS Chelsea Flower Show this May. The 100sqm exhibit will not now be at the show after at least 35 consecutive appearances.
At Chelsea, Interflora is promoting a British-grown cut flower message, a year after an Horticulture Week found that an RHS/Interflora Valentine's Bouquet that claimed to be British-grown was mostly imported flowers.
M&S will also push a British-grown flowers theme in the pavilion at Chelsea, in a display designed by Sallis Chandler.
The moves come as the UK's biggest cut flower grower Lincsflora, which supplies UK Horticulture and Waitrose, prepares to close.