I recently caught up with some friends who had just returned from backpacking in the Austrian Alps. As we chatted about their trip, they opened a bottle of zirbenschnapps, a traditional Austrian spirit (often homemade) flavored with a distillation made from the cones of Pinus cembra, the Swiss stone pine. After a few sips, my first thought was, “Where is Pinus cembra located in the Arboretum’s collection?” Looking up recipes for making zirbenschnapps came shortly after.
Pinus cembra is native to the sub-alpine zones of central and eastern Europe. Found in patches throughout the Alps and Carpathian mountain ranges, it has also been successfully planted and propagated in landscapes throughout the United States. This includes the Arnold Arboretum, whose two specimens were accessioned in 1918 and are located just off of Conifer Path. Currently our nursery holds four additional specimens which were wild-collected in 2001 from the Dauphiné Alps in southern France.
A comparatively rare pine within its home range, Pinus cembra is often out-competed by Picea abies (Norway spruce) and Larix decidua (European larch). This is particularly true at low and medium elevations. However, Swiss stone pine’s niche is the acidic and nutrient-poor soils of the sub-alpine zone between 4,000-8,000 feet in elevation, where the harsh climatic conditions keep its competitors suppressed or absent altogether. Under these conditions, the Swiss stone pine is famous for growing high above other trees, resulting in its regional nickname, “King of the Alps.”
Perhaps due to the conditions in which it thrives, Pinus cembra is also famous for being a slow grower. For example, neither of the two specimens off Conifer Path (both 100 years old, accessioned in 1918) look to have surpassed 40 feet; of the four 16-year-old specimens in our nursery, the mightiest stands at a modest 4.5 feet tall. If this seems diminutive for a pine, consider that these individuals are growing in favorable conditions—in the wild, some specimens may take over seven years to grow just one foot. On the other hand, slow growth is complemented by longevity. Mature individuals, which can reach 80 feet tall, have been recorded to live for several hundred years.
Flower and seed production usually begins after the tree has reached 40 years old. Once mature, Pinus cembra produces cones every two to three years. These cones remain on the tree for several years before dropping to the ground, unopened. In its native habitat, though, the vast majority of cones are plucked from the tree before they drop by Nucifraga caryocatactes, the Eurasian nutcracker. The bird breaks the cones open to eat the seeds, and stores those that it does not eat in shallow caches in the ground for winter. Nutcrackers lose a few of the hidden seeds each season and, as a result, have become the primary distributor of Pinus cembra throughout its native range.
Pinus cembra is widely utilized by human communities in the mountains as well. The timber is a preferred carving and building material, as it is lightweight, durable, and has a red tint and a pleasantly fragrant resin. Seeds from Pinus cembra cones are regularly harvested and make up a large share of the pine nuts sold in European markets. Finally, there is the zirbenschnapps, a traditional drink in many parts of the tree’s range. Sliced, soaked, and distilled, the cones add a flavor billed as “distinctly arboreal.” For those trekking in the Austrian Alps, being offered piney shots of zirbenschnapps may be almost as commonplace as sleeping in huts made from Pinus cembra timber.
After our last snows, the two accessioned specimens of Pinus cembra here at the Arboretum looked increasingly at home. With people skiing and snowshoeing underneath, it was almost possible to imagine the pair of trees in the Alps or Carpathians, rather than here in Boston. So, next time you are on Conifer Path, consider taking a detour to see Pinus cembra. Imagine the trees 8,000 feet up, on the leading edge of the tree line high in the mountains. If your powers of imagination are rusty, perhaps sip some zirbenschnapps to help you along. In any case, it is worth pausing now and again while exploring our collection to consider the diverse native ranges that our specimens hail from, as well as the many ecological and cultural roles they fulfill.