An early work such as Harvest demonstrates Knaths's mature style, characterized by strong line within a highly personalized cubist idiom. This signature style is the result of an interest in the distinctive manner of Matisse, as well as in the cubist masters Pablo Picasso, Juan Gris, and, especially, Georges Braque. Duncan Phillips applauded Knaths's synthesis of these influences, and, calling him "the American Braque," went on to say "…he has a similar plastic lyricism of soundly organized lines and tasteful, exquisitely related colors." In his estimate, Knaths "fills a given space with an order in which lyric and logic are almost as indivisible as in Braque."
In Harvest Knaths used line descriptively to define volume as well as space. Thick black lines outline the brightly colored still-life objects—the pumpkin, the turkey, and the barrel of apples—and also selectively indicate spatial recession, as in the floorboards. Textural effects are also evident, in the spotted breast of the bird and the grid-like pattern denoting the corncob kernels.
Phillips considered Harvest to be Knaths's masterpiece. He regarded Knaths "at his best as a colorist," and appreciated his unique cubist vocabulary, which in Harvest has the "effect...of a spacious room flooded with light and of reality electrified through rhythmical relations rather than objectified through realistic details."