Hips are the fruiting bodies of roses. But because of selective breeding for blooms in many varieties are sterile, or unable to be pollinated because of the abundance of petals, and hence produce no hips.
Of those that do produce hips – well not all hips are created equal… I currently use two types for cooking: Rosa Rugosa (alba); and Rosa Canina. To give them the English translation the Wrinkled Rose (White) originating from China and Japan and the Dog Rose which are native to Europe and the West/North-West of Africa.
Rosa Rugosa produces larger hips (about 2.5cm diameter), as slightly flattened spheres. They ripen earlier than Dog Rose and the season lasts much longer (August to November here). So I can get multiple pickings. I always leave about 20-30% for the birds in the early season as there is still a lot of other food sources, but into November I cut back to50%.
The good thing about Rosa Rugosa is the hips tend to be on the outside of the plant and easy to pick and when they are ripe the thorns drop off the stem of the hip – almost inviting you to pick them.
Dog rose, by contrast has skinnier hips maybe 2.5cm by 1 cm thick, on last years wood and therefore often protected from picking by this years growth. They are available later (October, November) and are trickier to pick without thick clothes and occasional swearing. Because of this and the time of year I rarely pick the full 50%. However, the hips keep better off the plant and you can have a few rounds at picking over a week without fear of losing the earlier harvest before you process the batch.
Both are prolific, and while I love the ease and bulk of the Rugosa rose hips the flavour is (to me) less intense and slightly thinner.