Solitary bees aren’t like honey bees that live in hives. As their name suggests, they make their nests on their own and lay their eggs in tunnels, such as in dead wood or hard soil. A bee hotel mimics these conditions, providing easily accessible space for egg-laying.
You can make your bee hotel whenever the mood takes you, but spring is when potential residents are queueing up for the best new abode. Sit and watch adult female bees find the nest on sunny days in spring. You’ll know they’re nesting if you see them flying in with pollen (some carry it on their bellies), with blobs of mud to create cell walls along the tube, or with bits of leaf (these are the Leaf-cutter Bees).
If you don’t have time or the right tools to make your own, then why not buy a ready-made RSPB bee hotel?