At this time of year I should be thinking about picking the green walnuts for pickling and making into liqueur de noix. Traditionally they are harvested in mid- to late July. You have to catch the fruit before the nutshell inside has got woody. The green fruits are fairly tough all the same, and you have to hack them to bits with a cleaver.
Green walnuts.Liqueur de noix is an infusion of chopped up green walnuts in vodka with sugar, spices and lemon zest. Walnuts contain a strong dye which reacts with the air to stain yellow and then progressively darker and darker until it is a very dark brown. Most instructions for making liqueur de noix carry on alarmingly about how the walnut juice will permanently stain everything it touches, but my experience is that if you just wash everything immediately after making the concoction, there isn't a problem. Cherries are much worse in my opinion, in terms of staining your fingers, clothing and spraying the wall with juice that doesn't come off paintwork.
Chopped green walnuts.
At first, a pleasant enough looking brew...
...but after 24 hours the chemical reaction causing the dark colour is well under way.
After three days it looks like you are habouring some sort of nuclear waste product, with the green walnut skins glowing lime green through the British racing green of the liquid.
By Christmas time it can be filtered and put in bottles ready for consumption. The longer you let it mature the smoother it becomes. Depending on your walnuts it will be more or less nutty, often with a touch of bitterness. It goes well on vanilla icecream and I often use it in any recipe I think is robust enough to take it, where the original recipe calls for amaretto.