Hi everyone
Is there any differences of shape, dimension, architecture between Pinus ponderosa and Pinus jeffreyi excepted for the cone (2 times bigger in jeffreyi) and the needles color (more blue in jeffreyi).
Thanks
Frederic
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In my highly amateur opinion ponderosa bark tends to lean more yellow- to orange-brown in colour, whereas Jeffrey leans more red-brown.
Apparently the prickles on the ends of the seed cone scales curve inward on one species and outward on the other, but I can never remember which corresponds to which.
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I seem to recall a friend of mine being able to pick them out from each other from above via aerial imagery due to differences in crown architecture. I’ll see if I can dig up the images where he was showing the difference.
I worked on a project where we were sampling pine trees in a mixed ponderosa-Jeffrey pine forest. They can be very tricky. Sometimes the only way I could be sure, was looking at my plot maps. As you already know, the pine cones are the easiest way. In addition to the size difference, the scale tips of Jeffrey pine cones face more inward, so ponderosa cones are prickly, and Jeffrey cones are smoother to the touch.
There are subtle differences that can help if you are comparing nearby trees. Jeffery pine bark is a little darker brown, and the needles have a darker, duller color. However, bark color is more useful in older trees, younger trees tend to look more similar. Ponderosa get lighter and more golden as they age.
The stronger differences are in chemical profile. If I can smell that vanilla/butterscotch, sometimes pineapple-like scent, then it is definitely Jeffrey pine. The problem with that, is that how strongly the tree is emitting volatiles can depend on time of year and weather. So it is most likely to be distinct on a warm summer afternoon, and not often helpful in cooler weather.
There are some differences in crown shape, but only in older trees. Jeffrey pine can lose it’s pyramid shape as the trees reach older ages, they tend to flatten out more in the canopy.
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Tom Chester (@tchester) wrote a comprehensive article on the distinctions a few years ago.
http://tchester.org/plants/analysis/pinus/jeffreyi_ponderosa.html
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A lot of times it can be pretty easy, but I’ll add that the degree to which these two species hybridize may be severely underappreciated. Note that quite a few other studies have been conducted since Haller’s 1962 dissertation. Phenology and other factors keep them separated pretty well, but I’ve read that in some survey plots/stands hybrids can account for as high as 40% of individual trees, and artificial crosses do well. I wish I could remember where I’ve read that, as most of the published stuff I’m turning up right now trying to remember are reporting rates in the 4-10% range. Anyhow, there are some stands of yellow pines north of Truckee, CA where that certainly seems like it could be the case - lots of head-scratchers on that landscape!
Also note that a lot of those color distinctions in Chester’s linked article may not apply elsewhere in the range of sympatry.
Lastly, I think there is still at least some open debate on where Washoe Pine lands in this mix, but I think most folks have settled on it being a Ponderosa variant.
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I’ve always heard that smell attributed to ponderosa pine (Pinus scopulorum, where I am in New Mexico). Personally, it’s got to be a warm dry afternoon for me to perceive it, but under the right conditions our local ponderosa pines certainly do have a vanilla-like odor.
I’ve spent little time around Jeffrey pine, so can’t compare the two.
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I notice that Tom Chester’s description says the odor is not apparent in dry weather, whereas my experience has been that I only notice it during early summer, when it is warm but the monsoon hasn’t begun. Of course, Pinus scopulorum may behave differently than the California plants. Tom Chester’s description suggests to me, though, that it isn’t really a difference between having or not having the odor, but that the odor is apparent under a much wider range of conditions for Pinus jeffreyi than for Pinus ponderosa. That would be consistent with my experience that people often describe ponderosa as having fragrant bark, but I can rarely detect it.
When you mentioned the cone, i thought you were going to mention the mnemonic we used to teach kids: “Prickly Ponderosa” and “Gentle Jeffrey.” Pick up the cone in the palm of your hand. If it feels sharp and prickly, it’s ponderosa; if it doesn’t, it’s Jeffrey.
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Just a warning that characters can vary regionally, and most comparisons are California-centric. Here in central Oregon, Ponderosas (P. ponderosa var. ponderosa) generally do NOT have prickly cones (their prickles are straight, but due to the scale shape do not stick out), so the prickly-gentle comparison misleads people. Cone size and shape and whether the prickles are straight or recurved seem to be the best characters other than location.
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This is a great question and a big topic. In my experience you can learn to distinguish them in your own neck of the woods, but that general rules don’t work, and the rules you develop that work in your area don’t work elsewhere :-)
The Pinus jeffreyi range is SUPER strange in my opinion and difficult to explain.
https://www.fs.usda.gov/nrs/pubs/jrnl/2021/nrs_2021_willyard_001.pdf
This study from 2021 suggest breaking Pinus ponderosa into three species, places P. jeffreyi on the same branch as Ghost Pine Pinus sabiniana, and makes the excellent recommendation that more attention is paid to Mexican species when taxonomic studies are done.
My understanding is that Ponderosa in the southern Rockies can give off that fragrance, but those in the Sierra Nevada never do. They’re different subspecies with different chemistries. I have no idea what’s driving the chemical differences though.
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As similar as the two pine species are, it’s interesting that the Jeffrey pine beetle can distinguish between the two and attacks only Jeffrey - http://forestry.nv.gov/jeffery-pine-beetle
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