First off, the cold hardiest English Walnut (Juglans regia) is concidered hardy to -5f (-20c) when fully dormant, and is suseptable to early or late frosts. Choose Carpathian or Hardy Persian varieties. More hardy varieties may be available now. An imposing tree to 60' tall and as wide, so not for small lots. It requires deep soil and equally deep irrigation. Bases of the trunks are to be kept dry buy excavating around the base of the trunks and applying coarse gravel or rock crush. Young trees need pruning to establish a central trunk and little afterward only to remove dead wood or correct the shape of the tree. More info can be found on the internet if these basic guidelines are suitable to your needs. Cheers, Barrie.
Juglans regia isn't English; it is from central and southwest Asia and southeast Europe (hence the more accurate name Persian Walnut). It can be a lot hardier than -20°C, with trees in its native area experiencing temperatures below -30°C in many areas, and probably down to -40°C in some. It does require a good warm summer to ripen the nuts; Vernon (July mean 19°C*) should be suitable for this in good summers but expect crop failures in cool summers. * http://www.vernon.ca/info/index.html
