I prefer to pick our courgettes when they are no more than five inches long, but dare to go away on holiday, or even a week-end and you will certainly find you have marrows. However, if you have a griddle or a grill, cut the larger courgettes lengthways into strips, remove the seeds & cover with a little oil and grill or griddle them. They will be much more palatable like this, chargrilled, than the mushy effect you get when boiling them & they will be much more digestible. . Incidentally, if you have enough plants to pick the courgettes when they are only three inches long they are deliciously edible thinly sliced raw with a tomato & onon salad and vinaigrette dressing.