Plant Species of San Jacinto Mountain:
Jeffrey pine, Pinus jeffreyi and ponderosa pine, P. ponderosa

This page was written in 2007. The information on this page is still correct, but I've learned a lot more about how to discriminate between these species in 2014. See Plants of Southern California: Pinus jeffreyi and P. ponderosa var. pacifica for much more information about these two species.

This page discusses these species as seen on the Devils Slide Trail. See also Distribution of Jeffrey pine, Pinus jeffreyi and ponderosa pine, P. ponderosa in a larger area of San Jacinto Mountain.

These two species both have long needles in groups of three, and are usually easily discriminated on the size of the cone here. The only other species on this trail with needles in groups of three is Coulter pine, Pinus coulteri, with very distinctive massive cones, found only near mile 0.4.

Ponderosa pines are found only below mile 0.3 (6700 feet elevation), and have cones shorter than 9.5 cm (3.7 inches). Jeffrey pines are found only above mile 1.10 (7200 feet elevation), and have cones longer than 12.0 cm (4.7 inches) that are typically twice the size of ponderosa cones. Thus all three species separate nicely in elevation along the trail, and one can glance at a cone and immediately discern the species.

Jeffrey and ponderosa pines are often lumped together and just called yellow pines because they are very similar species and many people are confused about how to tell the difference between them. As a result, some people think they ought to be combined into a single species. However, that would be literally an explosive mistake!

Resin from pine trees is heated to make turpentine. All pine species contain terpenes, except for two west coast species, P. jeffreyi and P. sabiniana, that instead contain aldehydes and heptane. Heptane is a highly explosive compound that was used to establish the zero point of the octane scale for gasoline. It is a big mistake to heat resin from either of the two pine species that contain heptane. (See also Conifers of California by Ronald M. Lanner, p. 62; and Discovering Sierra Trees by Stephen F. Arno, p. 11.)

Although people have a hard time distinguishing these two species, these are clearly two separate species. In addition to having different chemistry, they have very different ranges. Ponderosa pine is possibly the most widespread pine in western North America, whereas Jeffrey pine grows mainly in California and the nearby parts of Oregon and Baja California. Furthermore, the trees themselves know the difference; even in areas where both species grow side by side, they rarely interbreed. They have a number of barriers to interbreeding, including differing flowering times and problems in producing fertile seeds from crossing.

But people have good reasons to be confused because the two most commonly-used discriminants are almost useless here, at least in their simplest form.

Even many botanists have also been confused about these species (including me until 2006, when I finally noticed the size difference in the cones). The publication Non-wood forest products from conifers states Even a trained forester or botanist can have difficulty separating these two species. Also, the botanists doing the Vegetation Type Mapping Survey in the early 1930s made incorrect maps of the species distribution because they did not correctly discriminate the two species.

Most people use the gentle Jeffrey; prickly ponderosa mnemonic. Unfortunately, when dry, almost all cones here of both species are gentle, not prickly. When wet, almost all cones here of both species are prickly, not gentle. Thus this discriminant is utterly useless here in its simplest form. I was burned by this non-discriminating discriminant in the early plant trail guides I've done here, and mistakenly determined ponderosas as Jeffreys. (As of 10/11/07, I still need to correct the South Ridge and the Deer Springs plant trail guides and find the first true Jeffrey on those trails.)

As with most sayings, though, there is some truth behind this mnemonic; see Variation of Yellow Pine Cones With Moisture Content.

The other often-used discriminant is the smell in the deep furrows of the bark. Ponderosa is said to have no odor, or a resinous odor; Jeffrey is supposed to smell like vanilla, butterscotch, or pineapple.

Unfortunately, many of the ponderosas I've smelled at San Jacinto Mountain have a faint vanilla odor, and many of the Jeffreys also have a faint vanilla odor. Since Ponderosa pine is known to contain a sweet-smelling turpene, this is not terribly-surprising news. Thus smelling a faint vanilla odor is also useless for discrimination.

So far, to my nose, only Jeffreys have produced a strong vanilla odor, or any strength butterscotch or pineapple odor. If you smell that, you probably do have a Jeffrey (to be sure, I need to smell a lot more specimens now that I know how to reliably identify the species). Also, if you detect no smell, either your nose is not sensitive to the faint odor or you may have a ponderosa.

But why torture yourself using these unreliable or hard-to-use tests when there is a very simple way to tell the difference here? At least on the western slopes of San Jacinto Mountain, these species are easily discriminated by the length of the cones.

The cones of P. jeffreyi are nearly twice as long as cones of P. ponderosa. P. ponderosa has small cones 6.5 to 9.5 cm (2.5 to 3.7 inches) long; P. jeffreyi cones has large cones 12.0 to 17.2 cm (4.7 to 6.8 inches) long.

If your foot is about a foot long, simply step next to a cone. Ponderosa cones will be about one-fourth the length of your foot; Jeffrey cones will be half the length of your foot. See pictures below, taken at my house when I had slippers on, not on the trail; all other pictures were taken on the trail.

Alternatively, if you have a sheet of paper that is the usual 8.5 x 11 inches with you, just put the cones on top of the paper sideways and compare to the pictures below.

Of course, nothing beats sticking an inexpensive 6 inch = 15 cm ruler in your pocket for a quick measurement check on the trail. As seen in the picture below, this ruler is just about the size of the Jeffrey cones.

Cone from Jeffrey pine at mile 1.12 of the Devils Slide TrailCone from first Ponderosa pine on trail at mile 0.00 of the Devils Slide Trail
Jeffrey pine at mile 1.83 of the Devils Slide TrailFirst Ponderosa pine on trail at mile 0.00 of the Devils Slide Trail

Pretty easy, huh? I've verified this distinction on a number of trails on the west side of San Jacinto Mountain now. Once your eyes become accustomed to the sizes, you can simply glance at the cones and immediately tell the species. Furthermore, if you start on a trail below 7000 feet and begin with seeing ponderosa cones, as you hike up in elevation, you will say WOW, look at the size of those cones! when you come across your first Jeffrey.

Another distinction that seems to work most of the time, but which I haven't verified extensively, is the shape of the prickle on the cone scales, as shown in the following pictures (ignore the color differences which are due to different lighting, as can be seen from the same white piece of paper appearing blue in the left picture):

Jeffrey pine at mile 1.83 of the Devils Slide TrailFirst Ponderosa pine on trail at mile 0.00 of the Devils Slide Trail

The ponderosa prickle is stout, a nice solid pyramid (triangle as seen from the front) whose straight sides are roughly as long as the base. Ironically, the top part of the Jeffrey prickle looks much more prickly and dangerous! The Jeffrey prickle consists of a very slender top portion joined to the same lower portion as on the ponderosa, with a very distinct interruption in the slope of the sides in the middle. Botanists say that the Jeffrey prickle narrows abruptly to a slender tip.

Once you know what you are looking for, you can see this difference in the first pictures above of the entire cones.

Note added in 2014: the prickle difference turned out to be far from being 100% reliable. From much more experience, I now estimate it works only about 30% of the time.

The above pictures show that the prickliness of the cones is about the same, since the prickles for both are oriented at right angles to the scales; none of the prickles point outward to any significant degree.

The species separate nicely on elevation only on the western slopes of San Jacinto Mountain, at least in the vicinity of the Devils Slide Trail. P. ponderosa is found below roughly 7000 feet; P. jeffreyi is found above roughly 7000 feet. (P. jeffreyi is found in Garner Valley at 4400 feet, but that isn't the western slope of San Jacinto Mountain, right?)

On the Devils Slide Trail, there is a gap of 540 feet of elevation between these species. P. ponderosa is found at the trailhead up to mile 0.25 below an elevation of 6660 feet; most of the specimens in this area are at elevations below this trail. P. jeffreyi is found only on the upper part of the trail, beginning at mile 1.10 at an elevation of 7200 feet; most of the specimens in this area are in Tahquitz Valley above this trail.

Here is the distribution I recorded on 10 October 2007:

Locations of Jeffrey pine on the Devils Slide Trail (only the upper trail is shown)Locations of Ponderosa pine on the Devils Slide and Ernie Maxwell Trails (only the lower portion of the Devils Slide Trail is shown)

The deviation of the GPS points near Saddle Junction is typical; either the trail is not as shown on the topo map, or the reflections of the satellite signals on the boulders cause the GPS readings to be shifted slightly.

According to Minnich, the only extensive stands of Ponderosa pine in southern California occur in the western San Bernardino Mountains and here on the west slope of San Jacinto Mountain. See Distribution of Jeffrey pine, Pinus jeffreyi and ponderosa pine, P. ponderosa, at San Jacinto Mountain for the latest map of the distribution of these species here.

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Copyright © 2007-2014 by Tom Chester.
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Comments and feedback: Tom Chester
Updated 30 October 2014.