This year’s theme, Edible Britain, will result in community gardening groups creating 2,000 herb and vegetable patches in public spaces around Britain from 8 to 14 April," said a spokesman.
Last year’s Britain in Bloom was themed on wild flowers.
RHS community gardening groups, of which there are more than 3,000, can apply for free Mr Fothergills edible-plant seed packets from the RHS. Around 30,000 packs including chives and dill and edible flowers such as nasturtiums will be distributed to 2,000 gardening groups.
RHS community horticulture manager Stephanie Eynon said: "Britain in Bloom isn't just about pretty hanging baskets brightening up gloomy streets, it's about improving the environment, enhancing lives and bringing communities together through gardening."
More than 200,000 people spend 4.4m hours each year improving their communities, saving local authorities millions of pounds. On average, groups plant 115,000 trees, 352,000 shrubs and 21.6m plants and bulbs across Britain each year.
Britain in Bloom was set up 49 years ago as a tourist initiative but since the RHS took over 13 years ago has grown into one of Europe's largest community gardening and environmental campaigns.