The weekend events, to celebrate summer produce, are on 3 and 4 July - best time of the year to eat summer produce and encourage people to grow their own, says the RHS.
Wisley in Surrey will host a berry weekend, where visitors can try gooseberry - over 170 varieties - strawberry and redcurrant.
The festival at Rosemoor in Devon will offer guided garden walks and growing advice in the fruit and vegetable garden.
The grow your own weekend at Harlow Carr, Yorkshire, is dedicated to summer salads. Visitors learn how to grow salad plants and keep bees and chickens.
Hyde Hall in Essex hosts a strawberry fair with old-fashioned entertainment such as Morris dancing and advice on strawberries and composting.
Jim Gardiner, RHS director of horticulture, said: "Nothing says English summer time like fresh strawberries, raspberries and salads direct from the garden.
"The wonderful thing about growing your own is experiencing that just-picked flavour and we want to show it's quite straightforward to grow these crops in your gardens."