Pine trees, of the genus Pinus, make up around 120 different species of tree.
Evergreen conifers — evergreen meaning that they keep their leaves or needles all year round, and conifer meaning that they have cones — in the family Pinaceae, pine trees can be found throughout the world.
But if you’re wondering where do pine trees grow, the answer isn’t quite the same as if you were asking where pine trees grow natively.
Where Do Pine Trees Grow Naturally?
While pine trees will grow naturally in both the Northern and Southern Hemisphere, they are, with one exception, only native to the Northern Hemisphere.
That means that, while some types of pine tree have been planted extensively in the Southern Hemisphere on timber plantations for the wood and resin that they provide, pine trees would normally only grow much further north.
Human intervention has moved them to the Southern Hemisphere, and while there are economic benefits in the transplantation of pine species, the ecological consequences can be considerable, as I’ll discuss briefly below.
The one exception to the Northern-Hemisphere-only pines is the Sumatran or Merkus pine (Pinus merkusii), which is native to the Philippines, Laos, Vietnam, Malaysia, Cambodia, and Indonesia. It is on the IUCN red list as a vulnerable species, and its continued survival is threatened by deforestation whether due to logging, agriculture, or fire.
Where are Pine Trees Most Commonly Found?
The natural distribution of pine trees is in the Northern Hemisphere. Most commonly found in the northern temperate zone, which stretches from the Tropic of Cancer to the Arctic Circle, pine trees inhabit a huge range of countries.
To find out which USA planting zone you reside in, you should take a look at our article on hardiness zones by state and zip code.
What Habitat Do Pine Trees Live In?
In many high-altitude locations, pine trees define the tree line. The last elevation at which trees can grow before conditions become too inhospitable, the tree line’s exact altitude changes from place to place.
For example, there are high-elevation pines living in the mountains of California that live at 3660 meters (12,000 feet) above sea level, but in New Hampshire, for example, the tree line, along with its pines and other species, sits at about 1371 meters (4500 feet).
It’s thought that this discrepancy may be due not only to the severity of the winters, but also to the summer conditions: less summer in New Hampshire means less time for trees to recover from the previous winter.
There is evidence from Sweden that tree lines are changing in altitude as a result of climate change. The pine tree line in the Swedish Scandes has risen by 225 meters (738 feet) in the past century.
Pine trees can generally tolerate poor soils, so may be found growing at high elevations where the layer of topsoil is thin or in sandy coastal regions where soil fertility is very low. Some types of pine are also known as pioneer species.
For example, the Scots pine (Pinus sylvestris) was one of the first trees to re-colonize certain parts of Europe after the last ice age, and the pitch pine (Pinus rigida) is often one of the first trees to regrow after forest fires in its native areas of North America due to its evolved adaptations to fire.
The jack pine (Pinus banksiana) is another such example, growing in infertile soils and often having cones specially adapted to withstand (and only open after) extremely high temperatures.
Pine trees in general prefer full sun and don’t tolerate shade particularly well. As has already mentioned, they don’t mind soil with low fertility and will also grow in soil that’s fairly sandy. They like acidic conditions best.
As fallen pine needles increase the acidity of the surrounding soil, the habitat of a pine forest or a woodland with a large percentage of pine will be very different to that of a forest of broadleaved trees.
They tend to have fewer understory plants due both the soil’s acidity and to the fact that pine forests have relatively closed canopies (meaning that not much light reaches the forest floor).
However, there are some other trees and plants that will grow under pine trees, such as the silverleaf oak (Quercus hypoleucoides) in the Sky Islands mountain ranges of southeastern Arizona and northern Mexico.
Depending on the variety, you could find pines growing near the Arctic Circle in Scandinavia (Scots pine / Pinus sylvestris), on the southwestern coast of France (maritime pine / Pinus pinaster), or around the Mediterranean and into North Africa in Morocco and Algeria (stone pine / Pines pinea).
Where Do Pine Trees Grow in the United States?
There are currently considered to be 49 different species of pine native to North America. While many pine trees in the US can be found in the southeast and in the western mountain ranges, they also grow in New England, in the Great Lakes region, the Great Plains, the Rockies.
Different species of pine are native to different regions of the United States, and there is a great degree of overlap as well. What’s more, pines have been introduced into areas where they’re non-native, such as Kansas (one of the few states with no native pine species), although the ecological implications of that are not positive at all.
Ecological Consequences of Introduced Pines
Trees have evolved to live in harmony with their natural environments. They’ve also evolved to develop resistance to local pests and disease. But when their environment changes, either due to the effects of climate change or anthropogenic intervention, or because the trees themselves are planted somewhere different to their natural habitat, trees can suffer.
In Kansas and in other places in the US, for example, planted pines are currently being ravaged by the pine wilt disease. Caused by a nematode (microscopic, parasitic worm), pine wilt attacks are far worse in “exotic” species as native species seem to have some resistance.
What’s worse, the local environment can suffer too, and that can have devastating and far-reaching consequences. While conifers were introduced on a small scale to South America in the 19th century or before, large-scale plantation growing of pine species for timber and resin only began in the 20th century.
Since that time, pine trees have begun to spread out from their plantation sites by way of the copious seeds they produce, and small stands (groups) of pine trees are now beginning to appear across the Patagonian steppe.
This previously open landscape on which many species depend is being turned into a collection of coniferous woodlands far more rapidly than any natural evolutionary process would take place. There have been changes in the frequency of fires on the steppe, and biodiversity is declining as the number of “escaped” pines increases.
As the presence of so many pine trees also has the potential to encourage to arrival of pine-specific pests and diseases, the implications for the native ecosystems of South America could be catastrophic.
Similar situations have already been observed in other countries with large populations of introduced pine species (or of any introduced, non-native species of plant or animal), and yet we don’t seem to be able to learn from past mistakes.
As long as short-term economy remains more important than long-term environmental stability (and so long-term economy), the situation looks unlikely to change.
If You Want to Plant Pine Trees
If you’d like to plant a pine tree in your yard or garden, the advice is very much the same as always. Consult your local arborist or forestry association. Do some research and find out which species of pine is (or are) native to your local area. Work out the best types for your location, situation, and soil type.
If you are curious about the full reproduction cycle of a pine tree you should read my extensive article on how pine trees reproduce here.
It’s very important to remember though that, whatever tree you choose to plant, you should never take trees from the wild. Or at least, almost never: I have rescued several trees growing in incredibly improbable places, like the cracks in between paving stones or in a cement gutter by the side of the road.
If you see a tree in need, do your best to help if it’s safe (and legal) to do so, even if you have to go home and get a little trowel first!
Featured Image by treehouse1977 at Flickr
