If you are looking for a iconic garden to visit this summer (or winter) you should consider RHS Wisley. The place is sparkling, calm and friendly. You can even charge your electric car for free!* Take a picnic, eat at the excellent cafes or visit the extensive library of plants.
*Car charging is simple – you park at the electric charging point. Go to the entry kiosk get access to the charging point with a returnable deposit and top up your battery whilst pottering about.