Young leaves can be cimply rinsed and eaten raw (think salad or smoothie.)
Older, more bitter leaves are more palatable after blanching: add to boiling water for 2 min, then drain. Repeat if necessary. Such a treatment will take away some of the nutrients, but you can save the stock, which also promotes digestion.
To preserve a large harvest for off-season enjoyment, blanch and freeze.
Fruit leathers are a brilliant and simple way of preserving fruit, especially when it’s in excess or overripe and would otherwise go to waste. The basic principle is to purée the fruit (which can be combined to taste), spread it out and dry until no longer sticky. The “leather” can then be cut into strips or rolled up, will keep for a very long time, and is a handy healthy snack to keep on hand (no sugar needs to be added).
In this recipe, foraged blackberries are used to add flavour to the nourishing-but-plain-tasting haws, but the juice of other fruit (and a little sugar if really needed) can be added instead. Add a little water before step 2 if the pulp is too stiff. (Start with more information about foraging for haws.)