Plants support a diverse array of bacteria, including parasites, mutualists, and commensals on and around their roots, in the vasculature, and on aerial tissues. These microbes have a profound influence on plant health and productivity. Bacteria physically interact with surfaces to form complex multicellular and often multispecies assemblies, including biofilms and smaller aggregates. There is growing appreciation that the intensity, duration, and outcome of plant-microbe interactions are significantly influenced by the conformation of adherent microbial populations. Biofilms on different tissues have unique properties, reflecting the prevailing conditions at those sites. Attachment is required for biofilm formation, and bacteria interact with plant tissues through adhesins including polysaccharides and surface proteins, with initial contact often mediated by active motility. Recognition between lectins and their cognate carbohydrates is a common means of specificity. Biofilm development and the resulting intimate interactions with plants often require cell-cell communication between colonizing bacteria.