Like most other Proteaceae , Banksia violacea have proteoid roots , roots with dense clusters of short lateral rootlets that form a mat in the soil just below the leaf litter . These enhance solubilisation of nutrients , thus allowing their uptake in low @-@ nutrient soils such as the phosphorus @-@ deficient soils of Australia . B. violacea is highly susceptible to Phytophthora cinnamomi dieback .