The campaign - which has been packaged in an easy-to-read report aimed at consumers and which is supported by the HTA, the HDC and Horticulture Week - strives to highlight what horticulture offers to the quality and supply of British produce, the economy, the environment and the health of the nation.
NFU president Peter Kendall said at the launch: "We can show consumers how British horticulture contributes to these issues."
He added that his family has been involved in ornamentals and edibles production and hopes the campaign will highlight to consumers the diversity of the industry.
He said: "I know what an exciting and entrepreneurial sector horticulture is. It is an unbelievably diverse industry, ranging from vegetable growing to ornamentals to field and glasshouse production. We want to celebrate that diversity."
The Why Horticulture Matters report highlights the research conducted by the School of Plant Sciences at the University of Reading for the HTA - which pointed out the health benefits of exposure to plants and green spaces, and how wildlife and the wider environment benefit from plants and planting.
HTA business development director Tim Briercliffe said: "This campaign can only help raise the profile of ornamentals. Wildlife and the wider environment all benefit from plants and planting."
As well as the benefits of British ornamentals, the campaign - which is part of the NFU's Why Farming Matters campaign launched two years ago - also aims to show consumers why eating British fruit and vegetables is important, not only for our health but for the nation's economy.
NFU horticulture board chairman Richard Hirst said: "Growers are already providing solutions to many of the 21st century's key issues such as climate change and reducing food miles, and they form the backbone of the UK food chain. This is why horticulture matters."