4. Full Sun is Best
When you’re planting peonies (or transplanting an existing collection), then full sun tends to be best for the full benefit of the plant – although most types of peonies are known to cope just fine when grown in half-sun and partial shade instead, which is part of why they’ve achieved so much popularity as a flower that can grow almost anywhere in the world without issues.
When you’re planning out the positioning of your garden for the first time, the positioning of the planets in relation to one another (and to anything else that you might plant) aren’t the only factors that you have to think about. Also, consider the position of the sun and how this will affect your plants.
Also ask whether anything you’ve planted around the peonies could potentially shoot upwards and obscure the sunlight – yes, this is a common feature of badly-planned gardens that most people could have avoided just with a simple sketch of what gets planted where!