Around the middle of September, the nut season starts. Hazelnuts ripen in the hedges, and they have long been connected to folklore and legends. Hazel is associated to the Celtic tree month of Coll, from August 5 to September 1, and the very word Coll means "the life force inside you." Hazelnuts are connected to wisdom and protection, and are often found near sacred wells and magical springs. Hazelnuts can be used in workings related to divination and dowsing - tie a ripe one onto a string and use it as a pendulum.
In the British Isles, September 14 was the day when children would forage in the woods to collect hazelnuts, because this is when they are supposed to be perfectly ripe. In some legends, young maidens who go out a-nutting are in danger of becoming pregnant without benefit of marriage -- this is probably less due to the fertility associations of nuts and more to the fact that Nutting Day gave you a chance to be alone in the woods with your lover.
If you worked as a lacemaker, Nutting Day had a special significance. From this day until Shrove Tuesday in the spring, you could use a candle to light your work. Lacemakers spent long hours working at their craft for little pay, and because of the precise nature of their job, their eyes were often tired and achy by the end of the day. They were often advised to bathe their eyes in gin, which stung, but refreshed them enough that they could work a few more hours. The use of a candle permitted them to work longer during the dark winter months.
September 21 is sometimes called the Devil's Nutting Day, and it was the date on which mortals should never gather nuts. In some areas of Britain, nuts were not to be picked on Sundays, either. There's a story in the Warwickshire area that the devil himself was out gathering hazelnuts when he accidentally met the Virgin Mary (the story doesn't explain why Mary might have been wandering around in Warwickshire, but hey, it's an old story). He was so startled to see her that he dropped his bag of nuts, which turned into a hill called the Devil's Nightcap.