What are the best practices for designing and maintaining an urban bloomer garden bed in constrained city environments? Specifically, I am interested in a detailed discussion on soil composition, water management strategies, and integrated pest management approaches that are most effective under limited space and variable microclimate conditions. Additionally, insights into the selection of perennial flowering species that not only enhance biodiversity but also contribute to urban ecosystem services would be appreciated. How might the principles of permaculture be adapted to optimize the productivity and sustainability of such garden beds?