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• A. linearis plants lower their leaf temperatures through transpirational cooling • Low chlorophyll and high phenol could be acclimatized adaptive changes to heat • Soil quality and increasing temperatures negatively affect biomass of A. linearis • Younger plants invested more resources to ensure their protection and survival Mediterranean systems, such as in South Africa, are particularly vulnerable to the predicted increases in mean surface temperatures which will likely affect the growth and physiology of many plants and subsequently affect agricultural productivity. Aspalathus linearis (Burm.f.) R. Dahlgren (rooibos) is an important commercial, endemic crop that is produced in the Cederberg region, South Africa. This region experiences a Mediterranean-type ecosystem that is characterised by hot, dry summers (November – February) and cool, wet winters (May – August). This study assessed the effects of temperature on the growth and stress tolerant traits of A. linearis over two years. Crop biomass and selected physiological traits were determined in the field, along a temperature gradient, at four farm sites in the Cederberg during the summer and winter 2017 and summer 2018. Aspalathus linearis plants showed evidence of transpirational leaf cooling during summer and this, combined with lower chlorophyll and high phenolic content, could be considered acclimatized adaptive changes allowing the plants to mitigate the heating effects of elevated temperatures. Although changes in soil nutrients and increasing temperatures had a negative impact on crop biomass, the phenolic content, a measure of tea quality, did not vary with sites. This suggests that a shift in rooibos farming to cooler and wetter areas further south, for better growth and higher yields, would not compromise the quality of rooibos tea. [ABSTRACT FROM AUTHOR]