Pectic polysaccharides are major components of extendable primary cell walls and are amongst the most complex macromolecules in nature. The three major pectic polymers are homogalacturonan, rhamnogalacturonan I and rhamnogalacturonan II. Here we review the current understanding of how these structurally distinct polymers are integrated into primary cell wall pectic networks and how they function in cell wall matrices. We also review how the structure and properties of pectic networks can be modified in muro and how they can contribute to environments for the controlled slippage of the cellulose and cross-linking glycan network during cell expansion processes.