The ecological importance of root herbivory is increasingly recognized, yet root herbivores remain minor contributors to our overall understanding of plant-herbivore interactions. Given that plant defenses span the above- and belowground systems they represent a potentially important link that connects root herbivores with the foliar-based community (and vice versa). To explore plant defenses in an above/belowground context we utilized 2 different empirical approaches. First, we manipulated foliar and root herbivory on tobacco, measuring subsequent changes in secondary plant chemistry. Second, we reviewed studies that compare levels of secondary chemicals between leaves and roots to determine how plants distribute constitutive defenses. Last, we used meta-analysis to quantify the impact of induced defenses across plant tissue types. In tobacco the impact of root herbivory on foliar defense was variable and depended on where allelochemicals were produced within the plant. Nematode root herbivores interfered with aboveground defenses that have biosynthetic sites located in roots (e.g., nicotine), but had the opposite effect (i.e., elevated foliar expression) on chemicals produced in shoots. Results from our literature review suggest that constitutive defenses are extremely similar when comparing leaves with roots. However, based on a meta-analysis of induced defenses we conclude that: (1) foliar induction generates strong responses in leaves, but much weaker responses in roots, and (2) root induction elicits elevated defenses of equal magnitude in both leaves and roots. We discuss the importance of this asymmetry and the paradox of cross-system induction in relation to optimal defense theory and interactions between above- and belowground herbivory.