Olsen is lead scientist for the National Arboretum’s urban tree breeding program.
What do you do at the National Arboretum?
I was hired in 2006 as the urban tree breeder, so my job is to develop trees that are tolerant in urban conditions. Obviously, a tree growing in the urban forest has different stresses than trees in the wild or even suburban areas.
What sorts of stresses?
Urban trees have to be tolerant to compacted soils, which are low in oxygen. A lot of people don’t know that trees need oxygen. And soil salinity — all the road salts we use in winter are tough on trees … Historically our program has worked on American elm and red maples, among other trees. Now we’re working with more diverse number of tree species because really, diversity is what we’re up against. We need to have more diversity for our urban forest.
So are American elms and red maples what we see around D.C.?
We do have a large number of American elms around the city. We also use a lot of London planetrees. We’ve released a couple of hybrids. In fact, the London planetree is one of the most widely planted trees in the world.
What’s your favorite place within the Arboretum?
We have an old Osage orange. It’s one of the oldest planted plants on the grounds. It dates back to one of the farms and it’s on what we call Legume Hill. And if you’re underneath that tree and you look out across the Arboretum toward the Capitol you can’t see another building. If you do it just right you almost see no roads. You can stand at that point and look out toward D.C. and think you were in a forest in the Appalachians.
