Plants can adapt to their environment by varying the hydraulic integration of their xylem network. While much is known about xylem organization in aerial parts, roots have been less well studied. Johnson et al. measure xylem embolism resistance and connectivity in roots of two co-occurring tree species in a semi-arid habitat, Quercus fusiformis and Sideroxylon lanuginosum.They find that Quercus vessels are primarily solitary, while Sideroxylon xylem is highly connected, leading to resistant and vulnerable xylem networks, respectively. Pit membrane thickness plays less of a role in embolism resistance than expected, suggesting that xylem organization is an important trait that has yet to be fully explored.