The Cottage Smallholder

It all depends on the apple- we have a cooker in our garden that is ripe and ready to use in the first week of September and the first useable windfalls come down in late August, in our last garden the apples stayed on the tree right to November/December and were perfect then...wild crabs are the same, they have such varied parentage and varied enviroment both of which affect ripening. It just depends what you want the apples for. If they are for jam or jelly or chutney they will be better for being not ripe as they will improve the set of your preserves. Any small wild apple can be called a 'crab' apple- so many apple trees in the wild now are from cores thrown away by walkers/drivers that all sorts of apples can be found in hedgerows- they are all edible, just some are nicer than others, that's why humans started to breed apple varieties from wild apples. I would suggest trying your crab out for flavour- even when unripe, if it has a good scent and flavour ( get past the tartness and focus on the flavour) it will be worth using, if it has no scent, no flavour and the consistency of felt, find a better tree to scrump from! If an apple is ready to pick all you need do is gently lift it up and the stem will come away from the branch, wild crabs often do ripen later than 'domesticated' apples. Like wild blackberries, the quality and size of the fruit will be very varied, find yourself  a good tree, not just any tree.