Experts from The Royal Parks Guild – The Royal Parks alumni society - will be on site to answer any questions about food growing. Visitors can take away a variety of produce from both allotments for a small donation, including seasonal vegetables, potted herbs, homemade jams, and lavender bags.
Children will be able to help dig harvest the potato crop as well as enjoy activities such as face painting and animal petting.
Deputy chief executive Colin Buttery said: "Aside from being a great family day out, the harvest festivals at the demonstration allotments, provide the perfect opportunity to discover more about the excitement and enjoyment of growing your own food.
"I hope that people will be inspired to grow their own vegetables and herbs at home whether that is in a garden, on a balcony or even in a window box. Wherever people can find space to grow, there will be lots of advice on hand on how to get started."
In Britain harvest festivals are traditionally held on Sundays in September around harvest time. Any money made will be reinvested in the allotments.