Its a beautiful walk (it terms of scenery) and I truly recommend trying it out. A nice outing, fresh air and when you got to the top of the hill – beautiful views. The hike we did was called the Geological Trail and is approx. 3km (so not too far) but with all the hills and rests it took us a little over 1hr30min.
This info is a bit out-dated in terms of prices, but to find out more about the botanical gardens check out this link. Cost to get into the gardens is R30 per adult, and they have several hiking trails.
And even if you don’t want to go all out with a hike, stop by and check out the waterfall – its a straight walk from entrance to the waterfall, and a great place to chill and have a picnic (which is what we did after our hike).