Bract browning in waratahs (Telopea spp.) is not a localised calcium deficiency disorder

Bract browning in waratahs [Telopea spp. (Smith) R.Br.; Proteaceae] is a physiological disorder causing discoloration and necrosis of the margins and tips of exposed bracts. Experiments were carried out to determine whether calcium was involved in waratah bract browning, as browning and necrosis of leaf and bract tissue in other species such as lettuce and poinsettia has been attributed to a localised calcium deficiency. However, the inconsistent response of waratahs to calcium applied as a spray or to the potting media, and the lack of reduction in bract browning, suggests that factors other than calcium nutrition have a greater impact on the development and control of bract browning. This response corroborates reports questioning the role of calcium in late onset browning disorders.