According to enthusiasts like Clive Simms, anyone in England, or even southern Scotland, with a reasonably-sized garden could plant a walnut, provided that it is sheltered from cold winds and not subject to spring frosts.

As for "A woman, a dog and a walnut tree; the harder they are beaten, the better they be", he thinks the phrase originated on the Continent where long poles were used for harvesting nuts.

These knocked down both the walnuts and any dead branches, limiting the spread of fungal infections. This beating would have also stimulated late-summer shoot formation - useful for a plant that flowers at the tips of stems formed the previous year.

From The Daily Telegraph