This is a blog about the native conifers of the Pacific Northwest. It is a companion to the Northwest Conifers site. The blog will focus on timely and interesting details about our conifers, their connections to the rest of the environment, and our connection to them.

Sunday, October 27, 2019

Willamette Valley Ponderosa Pine

Ponderosa pine near Sisters, Oregon

Most of us in the Pacific Northwest are familiar with the ponderosa pine. Just the mention of it brings to mind its long needles and distinctive, golden bark. But where do you picture these pines growing? Most likely it’s east of the Cascade Mountains, perhaps around Bend. So, it might surprise you to find out that ponderosa pine is also native to Oregon’s Willamette Valley. The ponderosas of the Willamette Valley are adapted to the wet conditions found west of the Cascade Mountains. Even more surprising, these natives are better adapted to wet areas than the Douglas firs that grow in the valley. I remember that we had two large ponderosas growing in a particularly wet area on the farm where I grew up northwest of Eugene. Although I didn’t know a ponderosa from a pond-lily at the time, I remember the distinctive look of these trees.

Willamette Valley ponderosa
at Tualatin Hills Nature Park
The ponderosa pines that grow west of the Cascades and on the west slopes of the Sierras in California have been classified as a separate subspecies, sometimes called “Pacific ponderosa pine” (scientific name: Pinus ponderosa subspecies benthamiana). Those that have adapted to the wet conditions of the Willamette Valley are often called “Willamette Valley ponderosa pine.” Studies of ancient pollen show that these pines have been present in the Willamette Valley for over 7,000 years.

Willamette Valley ponderosa pines have long needles growing in bundles of three, like other varieties of ponderosa pine. The bark and cones also look similar. The needles and cones of the subspecies are a little shorter, and the bark is not as thick, but none of these differences are definitive. The key difference is that Willamette Valley can thrive in wet locations in the Willamette Valley. That alone indicates that they are clearly genetically different from the other trees of the benthamiana subspecies. Some have suggested giving them official status as a separate variety, with the name Pinus ponderosa variety willamettensis.  

Before European settlement in the 1850’s, ponderosas grew in scattered locations all over the Willamette Valley, mostly in wet, boggy areas along with ash, and on hillsides with white oak or Douglas fir. Like the ponderosas east of the Cascade Mountains, the Willamette Valley natives depend on frequent fires to eliminate competing conifers. These naturally occurring fires would burn up the grasses, shrubs and other competing conifers like Douglas fir and grand fir. But the thick bark on the ponderosas enabled them to survive these fires. The earliest inhabitants of the Willamette Valley understood this and used it to their advantage, setting fires to clear brush and other conifers. This maintained open ponderosa woodlands good for hunting. The European settlement of the Willamette Valley changed all that. These newcomers cut down the trees for lumber and other uses, turning the woodlands in the valley into farmland.   A sawmill was built in 1853 at Monroe, south of Corvallis, where there was a good supply of ponderosa pine. Sustainable forestry wasn’t a thing at that time. Soon all the nearby pines were cut down, and the mill closed. It wasn’t long before there were few ponderosas growing anywhere in the Willamette Valley. 

Willamette Valley pines
at the Oregon Garden
Recently, researchers wanted to see if they could restore ponderosas to the Willamette Valley. Plantings of east-side and west-side ponderosas on a test site near Corvallis determined that the east-side trees did not grow well in this wet environment. Any successful restoration would have to use seeds of ponderosas native to the valley. In the 1990’s researchers began collecting seeds from various Willamette Valley locations and growing trees in a seed orchard near St. Paul, Oregon. The seed orchard has provided seeds for restoration and planting in parks and other locations where the trees can thrive. Not much restoration has been done, but you can now find them here and there in parks.

The best location I’ve found for mature Willamette Valley ponderosa pines is the Tualatin Hills Nature Park in Beaverton. There are large ponderosas scattered here and there all over the park. Just look for the long needles on the trail and then look up. You’ll likely see a large ponderosa. 

Pine-Oak woods at the Oregon Garden
Willamette Valley ponderosa pines have been planted in many other parks in the Portland area. For example, Cooper Mountain Nature Park and the Tualatin River National Wildlife Refuge have plantings of Willamette Valley natives. 

The Rediscovery Forest at the Oregon Garden in Silverton has a section of Willamette Valley ponderosa pine. These were planted in neat rows in 2002. For comparison, some east-side ponderosas are planted next to them. Nearby, more ponderosas were planted with Oregon white oak, showing how these trees grew together 150 years ago forming a pine-oak savannah. 

Locations of Willamette Valley Ponderosa from Oregon Flora

Ponderosa at Hagg Lake
On a recent hike at Henry Hagg Lake south of Forest Grove, I was surprised to see a few ponderosas growing along the trail. Keep your eyes open when you are hiking on local trails in the Willamette Valley. You may see a Willamette Valley ponderosa pine. If the bark doesn’t have the bright colors of the ponderosas east of the Cascades, be patient. This only appears on very old trees. Enjoy these stately trees as they grow older. You may see the brightly colored bark in about 75 years.
More info

Ponderosa pines at the Gymnosperm Database