Knot gardens as rows of trimmed hedges like yew or boxwood were popular in the Elizabethan garden, according to Nichols’ English Pleasure Gardens, which I am still reading. It is the topiary style, where the plant is trimmed in such a way as to produce a particular effect in the garden. She says, “Topiary work added much to the variety of the parterre. The firm foliage of the dark evergreens, clipped sometimes into a straight hedge, sometimes into the most fantastic shapes, formed a background in charming contrast to the waving masses of brilliantly coloured flowers.”
Today if you visit Roseland Cottage in Stockbridge, Connecticut you can see swirls of well-clipped boxwood hedges with annuals planted in the center. The garden, established in the 1840s, was based on the ideas of nurseryman and landscape designer Andrew Jackson Downing, who often admitted his preference for the English style of garden.