Calcium is an essential macronutrient and signalling molecule needed by all plants to respond to stress and stimuli. However, in many parts of the world, calcium is in short supply, largely as a result of human-induced environmental change. Furthermore, unlike other macronutrients, such as potassium, calcium is unable to be remobilised when absorbed within plant tissue. So, plants need a steady supply for crucial signalling and defensive processes, particularly against pathogens (White, 2003). There are likely upwards of 30 possible calcium-related plant disorders which can cause issues such as reductions in tensile strength. (Shear, 1975; Lautner and Fromm, 2009). Susceptibility to these disorders increases because of both disease and calcium deficiencies, which have visible impacts on the world’s forests. Solutions to these problems require some understanding of calcium’s biochemical mechanisms and its importance for plant health.