What strategies can I implement for nesting sites in my pollinator garden?
As I continue to develop my pollinator garden, it's become clear to me that I need to do more than just provide food sources. I've observed many bees and butterflies feeding, but I'm concerned about the lack of suitable nesting sites. My garden is filled with lush plants and is designed with permaculture principles in mind, but I’ve not yet incorporated specific nesting structures. I've tried leaving some bare soil and brush piles, but I'm not sure if that's enough. What are some effective strategies or structures I can introduce to create nesting habitats for solitary bees and other pollinators? I'm particularly interested in pollution-free materials and low-maintenance options that would suit my Berlin climate.