Any 3-needle species will have a fair few needles in 4s when young, particularly on the lead shoot. Doesn't mean they will continue to do so as they grow older!

Very few pines have predominantly 4s on mature branches, and none that are hardy in your zone 5/6.

Resin

Pine needles are formed by a tiny apex that can be seen on young fascicles between the bases of the needles, and which usually dry up in a year. These are the growing points that can become activated to form an interfoliar shoot under proper circumstances. The primordial needles are formed in sequence within a fascicle budlet (which is inside the regular bud), so if the needle formation process is prolonged, an additional needle or even two needles can be added to the fascicle. Hard to explain without pictures.
There are no 4-needle pines, but there are 4-needle fascicles here and there. If a primordial needle on a 5-needle pine aborts, four needles are left and the missing one does not get replaced. If a 2 or 3 needle pine goes into overdrive, it can make some 4s, especially near the terminal end of vigorous shoots.
And when the 5-needle pinyon Pinus juarezensis hybridizes with the single-needle P. monophylla and the hybrid back-crosses, 4-needle fascicles may form (as well as 2s and 3s) and create the illusion of a 4-needle species P. quadrifolia.

I think you explained it very well if read with interest.

Thanks,

Dax

"There are no 4-needle pines"

Pinus tecunumanii (from tropical southern Mexico south to Nicaragua) has needles predominantly in fours.

Fours are also common (to predominant in some individual trees) in P. lawsonii, P. rzedowskii, P. squamata. All tropical / subtropical species.

Resin

I'll believe it when I see data. The same has been said incorrectly about "P. quadrifolia" for a centyry.

To elaborate a bit on my dog-in-the-manger attitude.
Yes, tecunumanii is given needle numbers of "4 (3-5)" by Farjon & Styles 1997. Rzedowskii is given as "(3-)4-5". Lawsonii is said to show "3-4(-5), very seldom 2". Even jaliscana is given as "4-5, rarely 3".
This is an antiquated way of expressing needle number, surely Farjon could do better, and probably would if not for an apparent hang-up about interspecific hybridization. Tecu has sometimes been considered a hybrid with relationships to oocarpa ("3, rarely 4"), and patula "(3-4)-5". And of course Farjon discounts my needle number studies of juarezensis because he cannot countenance non-taxonomists getting into that game. But the crossing results I cite (and others by other workers) clearly show intermediacy of needle number in hybrids, between their parents.
So I am skeptical of the "leap to fourness" when the possibility of hybridization is out there; or when specific studies are lacking. Words like rarely, seldom, and predominant don't cut it.I'm funny that way.

AFAIK, four is rare as a needle number, because it isn't a good packing setup for the needle primordia, not being a Fibonacci number (1, 2, 3, 5, 8, 13, etc). But I don't see why that should prevent it from occurring as a mutation, there are other plant species where 4 occurs as an unusual number, e.g. Potentilla erecta with four petals when other Potentilla all have five. And there's also Pinus durangensis with its non-Fibonacci needle number of six.

Resin

Sure, and montezumae and pseudostrobus also go to 6 occasionally, and one of the Mexicans, I forget which, goes to 8. You don't even need a mutation, if you have a slight developmental mistake of the kind I mentioned in my first post. I guess my larger point is that if 4s become present in high frequency along with 3s and 5s, hybridization would be worth asking about. I think needle number is a good trait to suggest genetic fooling-around, even though it can also come about innocently. So what frequency is necessary to call a pine 4-needled?

Now that you talk about pines with four needles, what is the common number in P. discolor. When I got mine, all its needles were in 3's, but after its first year, ALL its needles are in 4's. What may be an explanation?. Thanks

osprey

Hi Osprey,

It is usually 3s with a few 4s scattered among them

Resin

When you say ALL are in 4s, do you mean all the fascicles on this year's growth? Last year's? 2006? Exactly what?
I once did many counts on this species screening for evidence of crossing with edulis, but I don't remember finding 4s. Don't have access to my old data unfortunately.

Let me double check. I'm not sure about this year yet, I'll have to go and check. I think it has 4s since 2005.
By the way, there are no P. edulis growing in the region, but some P. cembroides may be found. I'll try to take some photos this weekend and post them on Monday.

osprey

3-needle pine saplings here like Loblolly, Loblolly x Pitch, & Longleaf saplings have occasional 4-needle bundles on vigorous sprouts. Similarly, 2-needlers like Virginia & Table mountain pines have some 3-needle bundles.

Ok, I was out there today again and was looking for more of the 4 needles trees. After closer inspection I found many clusters with 5 needles. One this particular tree, I found several with a cluster of 3, some with 4, and some with 5. I didn't have time to look at many others similar seedlings, but I'm guessing others are like this as well as I just chose this tree randomly to look at.

I took photos and will post later. This seems very odd. I would guess it's either a pitch x loblolly, shortleaf, or loblolly pine.

Thanks for the replies, John

pinetree30,

It turned out I was wrong, last year was mainly in 3s, with about 30-35% 4s. This is a photo of my P. discolor

osprey

I grew up in the bottom of Grand Canyon and some of the pinyons had 4 needles. My father and I ran the water pumps that supplied the North Rim 5 miles down the Bright Angle trail for years. Pop always told me there were double and single needle Pinyons so I was surprised to find 4 needlle pinyons. He cried B.S. so I took him a quarter mile up the trail from the Power House 5.2 mies down from North Rim and proved it. These needls were well formed and full lenth from the branch and on anchient looking trees. This was in the 1970's. I'm sure these trees still exist.