The pine family, Pinaceae, has 10 genera and 220 species. Members are almost entirely limited to the Northern Hemisphere, ranging from warm temperate climates to the extremes of tree growth north of the Arctic Circle. Worldwide, there are approximately 100 species of Pinus; 65 native to North America, with high concentrations of species in Mexico, California, and the southeastern United States. White pine (P. strobus) is common in the east along the Appalachians, and into the Maritime Provinces. Jack pine (P. banksiana) is prevalent in the Canadian forests across to Alberta. Pine forests are maintained by forest fires, which release seeds from cones, produce a suitable seed bed, and remove competing plants. Bristlecone pines (P. longaeva) have been documented to live more than 5,000 years.
Pinyon pine Figures (Pinus edulis) along with Utah juniper (Juniperus osteosperma) is the dominant tree of the Upper Sonoran Zone of the Southwest and Mexico (elevation 4,500 to 6,500 feet). It is a slow-growing, long-lived tree, with crooked trunk, seldom reaching more than 33 to 36 feet in height. Bark is reddish brown. Needles are in fascicles of two, approximately 2.5 to 3.0 inches long. The seeds, or pinyon nuts, are fleshy and wingless, and are avidly collected by a variety of animals as well as people. The European equivalent pine nut is gathered from P. pinea. Pines are of huge commercial value as sources of lumber, turpentine, and colophony (rosin).
Pines are entirely wind-pollinated. Anthesis occurs generally from May to June, but some species will pollinate later, and P. radiata, in the Bay area, will pollinate from January to March. In mid-Europe, pine pollinates from late April into July. Although pines produce copious amounts of buoyant pollen, rhinoconjunctivitis is not common, and sensitization is comparatively low. Wodehouse postulated evolutionary tolerance to pine protein, but others have suggested that elution of pine allergens is hindered by the waxy resin on the pollen surface Skin test reactivity to pines among allergic subjects in Arizona was 2%, in the Bay area approximately 3%, in Europe approximately 3%, but somewhat higher in New England at 6 to 10%. Case reports of pine pollen asthma are rare but well substantiated.
Conifers date to the Carboniferous era, 300 million years ago. Pinusspecies have the longest fossil record of the family. Separation of soft pines (subgenus Strobus) and hard pines (subgenus Pinus) occurred by the late Cretaceous period.1 Cross-reactivity between pine family members and other conifers in Cupressaceae is nonexistent.
Adapted for: Annals of Allergy, Richard Weber, MD, June 2002.