2-needle pines in the Monterey area, including possible 2-needle radiata

I've come across several 2-needle pines that I think might be Pinus radiata, which usually has 3 needles. I thought I'd share these observations and some thoughts on them. I'm interested in any comments folks might have.

Here are some pines observed in the Monterey area with 2 needles:

  • Pinus radiata (Monterey pine) usually has 3 needles, but "uncommonly" has 2 - this latter character being the main inspiration for this post. The seed cone scale tips are relatively smoothly rounded, some having minute prickles. The cones persist on the stems, but not as much as in muricata (< 20 yrs and usually much less in my experience). Pinus radiata var. binata has 2-needles, but is known from Guadalupe Island; similarly var. cedroensis has 2-needles, and is only known from Cedros Island).
  • Pinus muricata (bishop pine) has 2 needles. The seed cone scale tips have prickles of varying lengths, the Monterey Peninsula ones being markedly more prickled than radiata cones, as far as I've observed. The cones persist on the stems for a very long time, the longest I've counted was possibly in the region of 25 yrs - counted by counting whorls of cones from the branch tips back down along the trunk, assuming >=1 whorl per year..
  • Pinus pinea (Italian stone pine) also has 2 needles. To me the needles seem thick and stiff compared to radiata and muricata. The cone scale tips to me seem rounded in a different way to radiata scales - the rounding is bulkier. The cones width:length ratio seems larger to me. The bark looks a bit different too - to me it seems a bit more platy and between the plates, perhaps more pinkish. Mature plants have a broad canopy that looks like an umbrella, either due to natural (?) or human thinning of lower branches. Pinus pinea is introduced from Europe and seems to be increasing in range and abundance in the Fort Ord / Monterey area. The largest ones I've seen are planted beside the athletics track at Hartnell College and along Reservation Rd near Merrill Ranch. The younger ones tend to be in random areas within a mile or so of the larger planted ones.
  • Pinus contorta ssp. contorta (shore pine) has 2 needles that are a bit shorter than the others on this list. The cones are distinctly smaller than the others in this list. On subspecies contorta, the cones persist for "many years". This subspecies of contorta is native to the coastline of the Pacific Northwest, extending down into northern California. There's a few on the CSUMB campus as far as I can tell.
  • Pinus halepensis (Aleppo pine). Styer (2019) has one on the former Fort Ord. And @aparrot1 has one in the Las Palmas area.

Here are my observations of these taxa so far, starting with perhaps the most interesting ones.

List A: "2-needle radiata-like". I'm starting to think these are 2-needle radiata, and perhaps not muricata, as the "2-needle" character would initially indicate in keys. Their cones appear to be somewhat less persistent than muricata cones. In all cases, I've checked multiple fasicles on multiple branches before concluding that they are "2-needled". In all cases where I've been able to check, other trees nearby shared the 2-needle character, but 3-needle radiata were also not too far away. I've been ID'ing on iNat these as "muricata" just to keep them separate from the numerous radiata, but I suspect the proper ID might be radiata and I'll probably switch them over at some point.

List B. Straight-up 2-needle muricata long-prickled (northern & Monterey form) in the core of a well-known muricata area:

List C. 2-needle muricata short-prickled (southern form), possibly from Fort Ord Army planting and progeny thereof:

List D. Straight-up muricata (bishop pine) (or possibly attenuata, knobcone pine) alone in a previously unknown (?) location:

List E. Contorta ssp. contorta (shore pine)

List F. Pinus pinea (Italian stone pine)

List G. P. halepensis (Aleppo pine)

List H. Straight-up radiata

List I. Undecided

Side note: I'm wondering if the color of incipient female cones might be indicative:

Posted on May 21, 2022 07:39 PM by fredwatson fredwatson

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