In this article, we investigate the summability of the formal power series solutions in time of a certain class of inhomogeneous partial differential equations with a polynomial semilinearity, and with variable coefficients. In particular, we give necessary and sufficient conditions for the k-summability of the solutions in a given direction, where k is a positive rational number entirely determined by the linear part of the equation. These conditions generalize the ones given by the author for the linear case [?,?] and for the semilinear heat equation [?]. In addition, we present some technical results on the generalized binomial and multinomial coefficients, which are needed for the proof our main theorem.Summability, Inhomogeneous partial differential equation, Nonlinear partial differential equation, Formal power series, Divergent power series 35C10, 35C20, 40B05