As large organisms, trees face some remarkable challenges, particularly regarding long-distance transport and communication. In addition to moving water and nutrients from their roots to their leaves, they must also integrate cell-to-cell communication over large areas. Furthermore, to function as a single, cohesive organism, they must be able to effectively and efficiently send vital substances long distances along a network of cells, sieve-tubes, and vessels. But how effective is this cell-to-cell communication and how far can such solutes travel?