Luckily, the public gardens and the style these two pioneered live on. (I suppose some of the private gardens do as well as I imagine the firm's services were expensive.) You can see photographs of some of their work on their firm's website. Lots of plants, lush and lovely. They did not use only plants native to the garden's geographic area, but their work inspired people who are attempting to create more naturalistic landscapes. As much as I have always loved old roses, I doubt that I will ever attempt to have a garden of them again: too much fussing (even though they are WAY better than hybrid teas in that respect) and not enough wildlife sociability to justify their taking up valuable garden real estate. The work of Van Sweden, Oehme, and other pioneers has inspired lots of people to resist the tyranny of the lawn and the pruned evergreen.
It's not there yet, but some day, our front garden will be bold and romantic.
The muhlygrass/lovegrass combination is trying.
RIP, Mr. Van Sweden.