I’ll present you on the follow sites some mediterranean plants which you can grow with little protection outdoors over years. Also I’ll present you some forgotten german species.
You can’t convey experiences about the hardiness of bedded-out plants to plants in a cultivation pot. In case of severe frost periods the pot freezes completely so the plant will die. Bedded-out plants are compared with potted plants much more protected. The roots of well enrooted individuals reach to depths which also don’t frooze in severe winters. I advice you to bed out sensitive plants in the midddle of May so that the plants have enough time to enroot well.
A critical phase is also the early spring with a increasing sun. The sun heats the plants up so that they start with their budding or increase their metabolism at least. While periods of a froozen soil the plants will dry up. You can protect the plants from a heating by wrapping with fleece. Don’t plant species which are sensitive against late frost in front of a south-exposed wall, because their budding is antedated and the plants are much more vulnerable.