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, November 4, 2018

The Elusive Fir Cone Mystery

Douglas fir cone
Did you ever wonder why you don’t find fir cones on the ground? Well, cones typically cover the ground under Douglas fir trees. But Douglas firs are not in the Abies genus, the genus of the true firs. Like many conifers, Douglas fir cones open in late summer or fall and commit their small, winged seeds to the wind. The seeds descend like little helicopters, where most of them become tasty morsels for chipmunks, juncos and other small birds. Some time later, the cones drop from the trees to the ground. This is why the ground under mature Douglas firs is usually littered with cones. 


Cone near the top of a noble fir


Unlike the Douglas fir, you will rarely see a cone under a noble fir. In fact, if you see any cones under a noble fir, they are likely cones from a nearby Douglas fir. If you look carefully at the top of a noble fir, you may see cones up there. But the cones don’t stay there forever. So what happens to all the noble fir cones?









Noble fir scale and long bract
Noble firs, like all the true firs, engage in extreme seed distribution. The cones don’t just open and distribute the seeds. They completely fall apart and let everything fall to the ground, seeds, scales and bracts, leaving only a narrow spike of the cone core on the tree. The winged seeds generally separate themselves from the scales and sail off in the wind. The scales usually fall closer to the tree. Although you won’t find intact cones on the ground, in late summer and fall, the ground under a noble fir is often covered with these cone scales, with the bracts still attached.


Grand fir scale with broad bract



When you see these cone scales on the ground, you can use them to identify the species of fir. Recently hiking the University Falls Loop Hike in the Coast Range, I noticed some scales had fallen onto the trail. Attached to the scales were long bracts that extended beyond the edge of the scales. These long bracts are unique to noble fir among the native firs of Oregon. All of the other native firs have much shorter bracts, which never extend beyond the edge of the scales. 






Pacific silver fir scale with tapered bract

Later on the University Falls Loop, there were some scales along the trail with bracts that were much shorter than the scales. These fell from a grand fir. Note the shape of the tip of the bract. Each species has its unique shape. Grand fir has a broad end with a narrow tip. If you hike above 5000 feet in the Cascades, you're likely to see Pacific silver fir and subalpine fir. Pacific silver fir bracts are tapered at the end and come to a point. Subalpine fir bracts are rounded with a small point at the end.






Subalpine fir scale with rounded bract



So, if you are out hiking in the fall, just look down. You may see the cone scales all over the forest floor. Then you will know what happened to the fir cones. Not only that, but you will be able to identify each of the firs by the distinctive bracts of each species. 

Occasionally, you will find a fir cone, or even several fir cones on the ground. If you do, you should step away from the tree. It’s likely that a Douglas squirrel is cutting them loose and letting them fall to the ground. Douglas squirrels have no time for chasing after loose seeds. They will cut a cone loose and then strip the scales and eat the seeds, or store the cone in a cache to eat later. A favorite of the Douglas squirrel is the seeds of the Douglas fir. They can strip the scales from a cone and eat the seeds in about five minutes, leaving only what I call a “cone cob.” If you see Douglas fir scales on the ground, you can be sure Douglas squirrels have been busy at that location. You can often see piles of these scales and the left-over cone cobs below the squirrel’s favorite spot for eating lunch.


Douglas fir scales and cone cobs