Just got back from a week in the Azores - Sao Miguel and Terceira islands. The Azores are Portuguese islands in the middle of the Atlantic Ocean - 800 miles west of Portugal, and about 2000 miles east of Boston - volcanic islands, with a mild, San Francisco-like climate (coastal, rarely above 80 degrees fahrenheit, and rarely below 45 degrees).
It was interesting to see so many introduced trees in the Azores that are also popular as ornamentals here in San Francisco. Metrosideros excelsa (New Zealand Christmas tree - see photo above) is often used in the Azores as an ornamental, but it has also naturalized in the forests of the islands (which I’ve never seen here in California). The New Zealand Christmas tree in the photo above was a huge specimen in Ponta Delgada, the capital city of the Azores - so big that it had supports to hold up its limbs - if you look carefully you'll see the many vertical steel supports. Trees from the Araucaria genus are everywhere as specimen trees -- especially Norfolk Island Pine trees (Araucaria heterophylla). (The Norfolk Island Pine in the photo below was a young specimen just outside our hotel window in Angra de Heroismo, the largest city on Terceira Island- the hotel was in an early 1600s stone fort built by the Spanish during a 40 year period when they controlled the islands). And Pittosporum undulatum (Victorian box) is everywhere as a naturalized tree - to the point where there were forests of the tree - it has become an ecological problem on the islands.
There are trees that are native to the Azores - in fact endemic to them (which means that they found in nature only in the Azores). It was interesting to see native species that were closely related to trees I recognized, but which had developed into separate species as a result of the physical isolation of the islands. Laurus azorica, for example, was obviously a close relative of the Grecian bay (Laurus nobilis) that is found on San Francisco streets.
Because the Azores were isolated from Europe and North America for millions of years before the Portuguese arrived in the 1400s, the trees and plants evolved separately from their cousins in Europe and North America - which explains why there are so many unique species here. It also explains why introduced species from elsewhere are such a problem - the introduced species have no natural pests or diseases, and so they can out-compete the natives. Interestingly, Azores plants have been creating ecological troubles on other islands after being introduced - for example, the Azores’ evergreen fire tree (Myrica faya) is the main species to have regenerated on old lava flows in the islands. It was introduced to the Hawaiian islands, where it has threatened local flora there. (By the way, the Azores reminded me of the Hawaii islands with cooler weather - the island groups are both verdant, volcanic and isolated from other land masses.)
London plane trees (Platanus X acerifolia) line the roads everywhere in the Azores. The trees below were on a back road on Terceira island.
By the way, I highly recommend a visit to Parque Terra Nostra, a botanical garden near Furnas on San Miguel Island. The buildings here date to the 1700s, when Thomas Hickling, a wealthy Boston trader, built a home and introduced a number of trees and plants from North America. Subsequent generations of Azorean owners expanded the collection. In addition to a garden filled with endemic and native Azorean plants, there are beautiful plants and trees from other Mediterranean and semitropical areas of the globe, including trees from the Araucaria and Metrosideros genera, eucaplytus, redwoods, tree ferns, various palm species, and huge rhododendrons, magnolias, hydrangeas and camellias.
My favorite tree in the garden (and it was a surprise to see it) was a Wollemi pine (Wollemi nobilis). This is a tree botanists thought had been extinct for millions of years (they only knew it from fossil records) - until David Noble, an Australian hiker with some botanical knowledge, noticed some trees in a remote ravine in Wollemi Park, 200 miles from Sydney Australia. He brought some cuttings to scientists in Sydney, who concluded that Noble had discovered a “living fossil” - somehow, the 100 or so trees in that ravine had managed to survive - the last remaining specimens of their species. (Imagine if a hiker in a remote New Guinea valley had discovered a stegosaurus - it was like that for botanists.) Here’s a photo of me, next to the tree in the garden - not that it’s not very big, since no garden in the world has had one of these for more than 25 years!