On a quick trip to Cambridge last week, I really liked this border of Echium pininana (or giant viper’s bugloss) along the lawn behind King’s College, here. (The building is actually part of Clare College.)
A different kind of foundation planting.
The biennials, which are native to the Canary Islands, can grow as tall as 13′ (or 4 m.). They want well-drained soil, full sun, and shelter from wind.
Trinity College
I also liked this wide walkway border of Queen’s Anne lace and long grass at the entrance to Trinity College.
The tree on the right is a grafted descendant of the apple tree that inspired Isaac Newton.
enclos*ure 
a bit like stepping into Harry Potter.
Absolutely. And as a fan of the Hilary Mantel books, it was fun to see Anne Bolynn’s intials in the rood screen in King’s College chapel. Someone had neglected to remove them after her fall.
Because I first saw this plant in California, it is disconcerting to me to see it in such a historic British location!
It’s apparently a popular plant in England and Ireland. I would love to try it one day, but I don’t think it would care for tropical D.C.