Positive plant-plant interactions are important drivers of community assembly in environmentally stressful ecosystems, yet the ecological role of bromeliads as potential nurse plants in semi-arid rocky outcrops remains poorly understood. We investigated patterns of vascular plant richness associated with clumps of Encholirium spectabile, a rupicolous bromeliad endemic to the Brazilian Caatinga. Specifically, we evaluated how bromeliad clump size, plant growth form, seasonality, and cacti presence were associated with variation in plant assemblages occurring within bromeliad clumps. We sampled 155 bromeliad clumps distributed across 22 semi-arid rocky outcrops in northeastern Brazil during dry and rainy seasons. Generalized linear models and hierarchical partitioning analyses were used to evaluate the relative importance of ecological predictors associated with vascular plant richness. Associated plant richness increased consistently with bromeliad clump size, indicating that structural complexity strongly influenced plant assemblages within bromeliad microsites. Climbing and woody species exhibited higher richness than herbaceous taxa, suggesting functionally structured associations linked to bromeliad architecture. Cacti presence contributed to richness variation in isolated analyses but showed no independent conditional effect in the full multivariate model. Seasonal variation exerted comparatively little influence on total richness, although growth-form composition differed between dry and rainy periods. Our findings are consistent with the interpretation that Encholirium spectabile may contribute to the formation of structurally buffered microsites capable of supporting diverse vascular plant assemblages in environmentally restrictive rocky outcrop ecosystems. Given the increasing anthropogenic pressures affecting semi-arid rocky outcrops, preserving structurally complex bromeliad clumps may contribute to biodiversity maintenance and ecological resilience in these threatened landscapes.