Daneff, who was the Telegraph's gardening editor, joins the title, which launched last month to coincide with the Chelsea Flower Show, next month and takes over from launch editor Paula McWaters, who remains as contributing editor.
Gardenlife is the second publication launched by Seven Publishing, following last December's launch of Australian food magazine Delicious, which was backed by Jamie Oliver and other celebrity chefs including Rick Stein and Gordon Ramsay.
Daneff said: "Gardenlife is refreshingly different from anything else on the market. Its mixture of sound plant knowledge, beautiful photography and easy-to-follow practical ideas is exactly what's needed to encourage newcomers to gardening, as well as keeping keen gardeners inspired."
Seven has also announced that the deputy editor of Gardenlife will be former features editor of BBC Gardeners' World Magazine Martyn Cox.
Guardian Media Group took a 27% share in Seven in March this year, making it the single largest shareholder in the publishing firm, which is headed by managing director Seamus Geoghegan, former director of BBC Worldwide, and chairman Michael Potter, founder of Redwood Publishing.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .