Commercial director Mark Williams said: "This year, Waitrose has increased its range of garlands, trees and blooms for Christmas".
Christmas flower sales were up by 45 per cent year-on-year and Christmas trees up by 4.5 per cent on last year. Sales of poinsettias rose by 87 per cent week-on-week as customers entered into the festive spirit."
The supermarket chain, which has around 350 branches and 167 garden sales "pods", has an 8.2 per cent share of the grocery market in horticulture.
For outdoor plants this rises to 18 per cent, according to analyst IRI. Waitrose's total grocery market share is 5.2 per cent.
A Waitrose representative said: "Horticulture is one of the strongest areas of our business and is seeing some of the most significant growth figures (sales are up 13.2 per cent year to date).
"Our customer insight shows that after cooking, gardening is our customers' favourite hobby - and we have plans to build on current success by growing our offer again next year."