Semi-desert, foothills. Woodlands. Spring.
Mule Canyon, November 7, 2006.

The drought years of the early 2000s fostered the proliferation of the Ips Beetle (Ips confusus) which devastated millions of Pinyons in the Southwest. The Beetle is normally not a significant threat to the Pinyon Pine, but in drought years Pinyons cannot produce enough sap to close the holes the Beetles bore.  Thousands of Beetles attack a tree (you can actually hear them chewing) and kill it in a few months.  Needles die first; within a year or so the needles drop; and within two or three years the tree topples because its woody strength has been decimated.

Many homeowners who had gorgeous stands of Pinyons found themselves with hundreds of dead trees in the early 2000s.  A three acre plot of land often suffered the loss of 500 trees.

Such a massive die-off probably has not occurred for at least the past 500-1000 years, and although millions of Pinyons remain, it will take the arid Southwest centuries to regain the millions of mature trees it lost in just a few years.

Semi-desert, foothills. Woodlands. Spring.
Canyons of the Ancients National Monument, March 1, 2006.

Prolific nutting years such as the one the Pinyon at far left just finished, are often followed by several lean years, apparently because the tree exhausts its energy in the production of pine nuts.  Since Pinyon Pine nuts take 3 seasons to mature (as explained below) any particular Pinyon has a good crop cycle of about 4-6 years.

Pinus edulis almost always has two needles bundled together and the appearance of the tree is soft as in the photo at far left. The rare single needle tree looks thin and prickly, as shown in the photo at near left.

Semi-desert, foothills. Woodlands. Spring.
Mesa Verde National Park, May 31, 2004. 
Canyons of the Ancients National Monument, September 19, 2005 and May 25, 2016.

Pinyon Pine, as all Pines, is monoecious, that is, pollen bearing (male, "staminate") structures (top photograph at left) and seed-bearing (female, "pistillate") structures (middle photo at left) are separate but on each tree.

Pinyon Pine nuts take 3 seasons to mature: minute cone buds are formed; a small cone grows, opens, is pollinated, and closes; this cone reopens allowing the pollen inside to fertilize the eggs.  Growth is then rapid and the green, sappy, two inch seed cone matures, dries to light brown, and opens from September to November of the third season.

The following spring begins the ballet, in this case a pas de deux.

The dancer on the right

has shed its crown and its arms swirl in freedom.

The taller dancer at left has its arms still encased in the Pinyon shell but is obviously delighting in forming a billowing basket.

Light colored seed husks are almost always empty; good seed husks are usually dark brown (as in the bottom two photographs at left).  The buff-yellow pine nuts inside the good husks are a  mainstay of many Colorado Plateau critters-- including Al and Betty.

Before the growing cycle begins again, it is common for several years to pass. Thus seed production is on about a four to six year cycle, a bit more frequent than the often stated seven year cycle.  The seven year cycle myth dates back at least to the mid-1870's: The botanist Townshend Brandegee states in his "Flora of Southwestern Colorado" (part of the Hayden Survey report for 1876) that Pinus edulis "is said to fruit once in seven years".

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Pinus edulis