In an anisotropic porous matrix with a Soret coefficient, the onset of double-diffusive convection is investigated analytically using weakly nonlinear analysis. The momentum equation is expressed using a generalized Darcy model with a time derivative term. The Newell-Whitehead-Segel equation is acquired, thereby examining the Eckhaus and zigzag secondary instabilities. Nusselt and Sherwood numbers are used to examine convection onset by quantifying heat and mass movement. Heat and mass transmission dynamics are graphically depicted as a consequence of several parameters. An increase of the positive value of the Soret parameter enhances heat transport, whereas, an increase of the negative value of the Soret parameter reduces it.