Only a few tree species inhabit Yellowstone and the most common tree is the Lodgepole Pine or Pinus contorta. The common name “lodgepole” comes from their tall, thin, straight trunks which were used to make Indian lodges and teepees. They have two needles per fascicle or bundle and grow up to 75 feet tall here.
Eighty percent of the trees in the park are lodgepole pines. They grow so well here because the rhyolite (lava) soils are shallow, acidic and not very nutrient- rich. Lodgepoles have a shallow root system and don’t require very good soil to grow. They also like full sun and so are good pioneer species, easily moving into an area after a disturbance like fire.
The ones in a thick forest look like lollipops, with tall thin trunks and foliage or needles only at the top where they can get sunlight. The trees on the edge of a forest or out alone in a meadow, however, can have branches and needles all the way down to the ground because they’re not shaded out by other trees. Since they are self pruning, the lower branches will eventually lose their needles, die and fall off if other trees grow nearby and block the sun.
Most interestingly, Lodgepole pines are a fire-adapted species. They have two types of pine cones. One is like most other pine trees—it opens up as it matures and releases its seeds. With lodgepoles, this takes about 2 years. But Lodgepole also have a serotinous cone which can remain on the tree for many years. It is glued shut with a waxy coating.
It takes the heat of a fire to melt off the resin so that the cone can open and release its seeds. This means that after a fire, the lodgepoles’ serotinous cones open, naturally reseeding the area. So all the young lodgepoles you see growing in burned areas of the park were not planted by rangers, but by fire itself.
As you travel through Yellowstone, you can’t help but notice the vast forests of young and mature lodgepoles. Hike in and hear the trees squeak and crack as they sway in the wind. You may hear red squirrels chattering or glimpse a pine marten or great gray owl. Lodgepole forests often shelter wild strawberries and grouse whortleberry, a ground cover the bears also enjoy eating.
Beware falling limbs and even trunks on windy days. There are still many standing dead trees since the fires of 1988 and subsequent annual summer fires. Those tree skeletons fall easily. Strong winds can even topple live trees since the roots are shallow.
The ability to withstand poor soils and short growing seasons and reseed themselves, like a phoenix rising from ash, make Lodgepole pines a special forest specimen. The most common tree in Yellowstone is anything but common—it has evolved exceptionally to thrive in just this sort of place.