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Ponderosa Pine
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Ponderosa Pine

Ponderosa Pine

Ponderosa Pine branch
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Scientific classification
Kingdom:Plantae
Division:Pinophyta
Class:Pinopsida
Order:Pinales
Family:Pinaceae
Genus:Pinus
Species:ponderosa
Binomial name
Pinus ponderosa

Ponderosa Pine (Pinus ponderosa) is a widespread and very variable pine native to western North America. See the table below for the botanical characters of the different types.

In most texts separated into two varieties, forestry research has shown that there are four different taxa in Ponderosa Pine, with differing botanical characters and adapted to very different climatic conditions. These have been termed "geographic races" in forestry literature, while some botanists have historically treated them as distinct species. In modern botanical usage, they best match the rank of subspecies, but not all of the relevant botancial combinations have been formally published yet. These are as follows:

Pinus ponderosa was first discovered by David Douglas in 1826 in eastern Washington near where Spokane now lies. This is within the area of the "North Plateau race", and this therefore is the type subspecies.

Range map of Pinus ponderosa and Pinus arizonica.

The distributions of the subspecies, and that of the closely related Arizona Pine (Pinus arizonica) are shown on the map. The numbers on the map correspond to the taxon numbers above and in the table below. The base map of the species range is from Critchfield & Little, Geographic Distribution of the Pines of the World, USDA Forest Service Miscellaneous Publication 991 (1966).

Before the distinctions between the "North Plateau race" and the "Pacific race" were fully documented, most botanists assumed that Ponderosa Pines in both areas were the same. So when two botanists from California found a distinct tree in western Nevada in 1948 with some marked differences from the Ponderosa Pine they were familiar with in California, they described it as a new species, Washoe Pine, Pinus washoensis. However, subsequent research has shown that this is merely a southern outlier of the typical "North Plateau race" of Ponderosa Pine.

Table of characters distinguishing the subspecies of Pinus ponderosa and Pinus arizonica

Taxon 1 North Plateau  2 Rocky Mts  3 Southwest  4 Pacific   5 Arizona  6 Storm's 
 Character  (ponderosa (scopulorum (brachyptera (benthamiana  (arizonica (''stormiae) 
 Needles per fascicle 3 2-3 2-3 3  4-5 3-5
 Needle length 10-22 cm 8-17 cm 12-21 cm 15-30 cm  12-22 cm 20-30 cm
 Needle thickness 1.7-2.2 mm 1.5-1.7 mm 1.6-1.9 mm 1.3-1.7 mm  1.0-1.1 mm 1.0-1.2 mm
 Cone length 5-11 cm 5-9 cm 5-10 cm 7-16 cm  5-9 cm 6-11 cm
 Cone scale width 14-19 mm 16-20 mm 14-19 mm 18-23 mm  15-18 mm 12-17 mm
 Immature cone colour purple green green green  green green
 Mature cone surface matt matt glossy glossy  glossy matt
 Seedwing : seed length ratio  1.9-2.5 2.1-3.4 3.0-3.5 3.0-4.7  2.8-3.2 3. 0-3.5
 Max tree height 50 m 40 m 50 m 70 m  35 m 20 m
 USDA hardiness zone 4 4 6 7  7 8
Notes:
Taxon numbers refer to the map
Needles per fascicle - the most frequent number is in bold
Seedwing : seed length ratio - high numbers indicate a small seed with a long wing; low numbers a large seed with a short seedwing