In the archivist's garden

Do you know this Edinburgh garden?

I've been asked to contribute a tip to a tourism website giving a "local's secret". I chose Scotland's People Centre, where, if you know the little path between Register House and New Register House, you can find this garden. There are over 50 plants associated with Scotland there. I took photographs today, but this one seemed to stand out among the others. Even found an agapanthus still in bloom there, and some sea thrift.