The regular Friday programme has made way for football and tennis this summer as well as having its time and format changed for the Chelsea, Hampton Court, BBC Gardener's World and Tatton Park flower shows.
Numbers dipped to 1.38 million on 18 June. The 40-year-old show attracted five million viewers in its Alan Titchmarsh-presented heyday and averaged two million even in recent years.
A BBC representative said: "This year, Gardeners' World viewing figures are generally in the 1.8-2.2 million bracket except for the occasional dip, and it is often the highest-rating programme on BBC2 on Friday nights."
But he added: "However, the beautiful weather and the World Cup undoubtedly kept some people away from the television during June and July. In addition, Gardeners' World gave way to major sporting and music events taking place during the summer, including Wimbledon and the Proms.
"During the downtime, we posted 'Jobs for the Weekend' on the website so viewers would get essentials each week. Gardeners' World 30 July edition bounced back with a solid 1.9 million viewers."
GARDENER'S WORLD VIEWING FIGURES
Week ending 15 August No show
Week ending 8 August TBC
Week ending 1 August 1.9 million
Week ending 25 July (RHS Tatton Park) 1.7 million
Week ending 18 July No show
Week ending 11 July (RHS Hampton Court) 1.81 million and 2 million
Week ending 4 July 1.49 million
Week ending 27 June No show
Week ending 20 June 1.38 million
Week ending 13 June 1.46 million
Week ending 6 June 1.88 million
Week ending 30 May (RHS Chelsea Flower Show) 1.91-4.52 million