The tram ride to the gardens ends in an unpromising vista of urban motorway and a slightly fiddly crossing and 10 minute walk to the entrance, but it is worth persevering - and the road is inaudible in the garden. Admission is free.
The botanical garden was founded in 1923 and is an excellent example of a naturalistic garden that takes advantage of the low hills and rocky outcrops surrounding the city. The main focus is on alpine and Himalayan collections, both of which are outstanding, but these are interspersed with more formal and historic-style gardens, e.g. of a traditional Swedish manor house. There is a lot to see, whether one sticks to the well-maintained paths or, if sufficiently mobile, uses the rock steps up to the viewpoint and Korean grove. It's worth photographing the map on entry to make sure you don't miss anything. A visit could take anything form one to two hours.
There are paths leading from the garden to the surrounding nature reserve. Be sure to take the gate by the Korean/Japanese grove (signposted to Asian arboretum) and walk a few yards into the reserve; there is an enchanting lake just inside.
The gardens are very well-cared for. There are ample toilets and the cafe serves a wide range of food with quick self-service, e.g. salads, sandwiches and soup. The shop is modest in scope. New glasshouses open in 2025.