It is said that the walnut tree thrives best if the nuts are beaten off with sticks, and not gathered. Hence Fuller says, “Who, like a nut tree, must be manured by beating, or else would not bear fruit” (bk. ii. ch. 11). The saying is well known that-
A woman, a spaniel, and a walnut tree, The more you beat them the better they be.
Taylor, the Water-Poet.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894