The Best of Experts is Hessayon's selection of the best of his 24 gardening titles, written since 1959. Hessayon's books have sold more than 50 million copies since the first Expert book came out in 1959.
Hessayon threatened to retire in 2007 but since then has published The Orchid Expert in early 2008 and revised The Green Expert in 2009. His publicist Gareth Pottle said: "We expect The Best of Experts to be the best-selling gardening book this year.
"I saw the doc last Friday. He's still on good form and is working on the 2011 Expert and making plans for more Experts after that. His work rate appears to be getting faster now that he's in his 80s."
Pottle added that the subject matter of the latest publication is "all hush-hush at the moment — we don't want our many imitators to get an early lead".
The book will retail at £7.99 and will be published by Transworld on 1 April. Two extensions to the franchise will come out on 30 April, The Cat Expert and The Dog Expert, billed as the only books that lovers of the pets will ever need.