During and for some years after the Second World War schoolchildren collected rose [Rosa spp.] fruits – hips – which were used in the manufacture of rose-hip syrup. Lack of imported citrus fruits led to worries about children getting sufficient Vitamin C which is found in rose hips.
For example:
Children in Northumberland and parts of north Durham gathered rose hips and sold them; for several years I and several friends did this each autumn.
The man who started the practice was a friend of my family … Mr Norman Pattison and he worked for the firm of Scott and Turner, the makers of Andrews Liver Salts, at their factory in Gallowgate, Newcastle-upon-Tyne.
In his early years with the firm he was a delivery driver, and when the company first began to make Delrosa, before the Second World War, he gathered wild rose hips for them. Then his wife joined in, and more of his friends and relatives. Mrs Pattison was a former teacher of girls’ P.E. at Jarrow Grammar School, and was a close friend of my aunt, also a teacher. So when I started at that school as a pupil in 1941, Mrs Pattison had enlisted the help of at least two of her former colleagues on the staff, who organised groups of pupils (almost every one of us girls) to go out in late September and October, on Saturdays (I don’t recall Sundays) and gather hips from the hedgerows. Two teachers – the Geography and Botany mistresses – combined the hip gathering with field studies in the own subjects, and we enjoyed these outings, apart from the scratches!
Our rose hips were weighed and Scott and Turner paid us 3d a pound for them; I know we received a letter from them telling us how much we were contributing to the war effort by enabling more rose-hip syrup to be made – a valuable source of Vitamin C, which would maintain our health during wartime [Heworth, Tyne and Wear, December 1985].

According to the Journal of Botany, 78: 269 (1940), elsewhere in Europe:
German scientists have found that the hips of Rosa canina [dog rose] are a rich source of the anti-scorbitic Vitamin C. The German State Railways are therefore using their tracks for growing this species; half a million plants are to be acquired for this alone, and other waste land is to be utilised.

Image: Canvey Island, Essex; August 2014.

Updated 25 August 2014.