American white pines
02, 2005 18:27 PST
Bob, et al.,
White pines have always been the most interesting to me.
I used to call them five needle pines but now must make a
change. Most of the pines in southern Mexico are five needle,
even though they are hard pines. Actually many have four or
five, with some having even 6, 7, or 8.
Of the North American white pines, I find P. monticola the most
variable. In central California it is found near timberline, up
to 3,300 meters. Here it can be a large tree, developing deep,
vertically furrowed bark that is often bright orange or maroon
when mature. In the Puget Sound near Seattle, the tree has
relatively thin bark that remains gray, even in age. Likewise in
Idaho, but the bark is thicker, often forming perfect checks,
leading to the name alligator pine which was one of the early
common names. The easternmost population, in Avalanche Valley in
Glacier National Park, is quite the site to behold. Here, just a
few kilometers from the continental divide, the pine grows with
Tsuga, Thuja, and Acer, reminding me of the forests along Lake
Superior. There is even an understory Taxus to make the picture
complete. Here, the pine has the thick bark in long, vertical
like its Lake Superior counterpart. If it were not for the
occasional Pseudotsuga, it looks alot like the Porkies. Even
though the species are different, it suggests to me an ancient
connection that was separated by the formation of the Great
The Mexican cloud forest Pinus strobus grows only in the very
wettest forests and has relatively thin, tightly plated bark.
Its closest relative is P. ayacahuite, which is a truly
magnificent tree growing in slightly drier, mesic sites on a
wide variety of mountains throughout Mexico. This tree is
reminiscent of the magnificent P. lambertiana with huge,
dramatic crowns of great character. The dry form of this tree,
var. vietchii, makes enormous cones up to 65 cm long.
So far all the pines I have mentioned have seeds with full
wings. A third variety of P. ayacahuite, var. brachyptera, has
seeds with reduced wings. It grows in central Mexico. Partly
overlapping in range and continuing into central New Mexico is
P. strobiformis, sometimes known as P. flexilis var. reflexa.
The seeds of this mountain pine have only the tiniest remanant
of a wing. It is here where the pines begin to depend on corvids
for their dispersal and not the wind. The furthest north of this
multi-species grex is P. flexilis, a true nut-pine.
So this story of closely related pines comes full circle in
Idaho, where P. monticola and P. flexilis both occur, although
now with widely different ecologies. All of the pines I have
mentioned are known to hybridize with each other where their
ranges overlap, forming this giant range covering most of North
America. The only exception is P. monticola and P. strobus,
which are separated by a few hundred kilometers of North Dakota
and eastern Montana.
The wonders never cease…