The reliable sampling of root exudates in soil grown plants is experimentally challenging. This method shows how to sample citrate from rhizotron grown plants with ZrOH DGT gels to produce high resolution citrate imaging. The DGT technique is based on thin hydrogels with homogeneously distributed analyte-selective binding phases and is used for 2D visualization and quantification of the distribution of labile (i.e., reversibly adsorbed) analytes.