• Mediterranean‐type ecosystems contain 20% of all vascular plant diversity on Earth and have been identified as being particularly threatened by future increases in drought. Of particular concern is the Cape Floral Region of South Africa, a global biodiversity hotspot, yet there are limited experimental data to validate predicted impacts on the flora. In a field rainout experiment, we tested whether rooting depth and degree of isohydry or anisohydry could aid in the functional classification of drought responses across diverse growth forms. • We imposed a 6‐month summer drought, for 2 yr, in a mountain fynbos shrubland. We monitored a suite of parameters, from physiological traits to morphological outcomes, in seven species comprising the three dominant growth forms (deep‐rooted proteoid shrubs, shallow‐rooted ericoid shrubs and graminoid restioids). • There was considerable variation in drought response both between and within the growth forms. The shallow‐rooted, anisohydric ericoid shrubs all suffered considerable reductions in growth and flowering and increased mortality. By contrast, the shallow‐rooted, isohydric restioids and deep‐rooted, isohydric proteoid shrubs were largely unaffected by the drought. • Rooting depth and degree of iso/anisohydry allow a first‐order functional classification of drought response pathways in this flora. Consideration of additional traits would further refine this approach.