Beneath the surface: Seed bank homogenization and multiscalar variation in Boston's community gardens

Urban community gardens are often assumed to enhance fine‐scale biodiversity, yet repeated disturbance and shared horticultural norms may also contribute to urban biotic homogenization—the convergence of species composition across spatial scales and sites within the urban matrix.

We conducted a seed bank emergence trial over 16 months across 350 plots in 37 community gardens spanning eight neighbourhoods in Boston, USA, to assess how germinant abundance, diversity and composition varied across plots, gardens and neighbourhoods, and to identify key landscape and management predictors

Across the garden network, the seed bank was dominated by introduced annuals with traits linked to disturbance tolerance and rapid colonization, indicating a broad prevalence of ruderal life‐history strategies.

Despite this dominance, abundance, diversity and community composition were variable within and among gardens.

Garden‐level variables—particularly abandonment rates and total crop abundance—were the strongest predictors of seed bank abundance and diversity, though predictors were detected across multiple spatial scales.

Notably, garden‐level abandonment was associated with lower germinant abundance and diversity, complicating assumptions that visible weedy vegetation inherently reflects neglect

Together, these findings show that spontaneous vegetation in community gardens emerges relationally through interactions among gardener practices, shared norms and urban context.

Recognizing how management shapes urban soil seed banks can inform more flexible and inclusive green infrastructure design.