Twenty (18 depending on latest reference) of the more than 100 species of Pinus on earth. All of these pines are native to the state of California. 1. Monterey Pine (P. radiata), 2. Bishop Pine (P. muricata), 3. Santa Cruz Island Pine (P. remorata), 4. Whitebark Pine (P. albicaulis), 5. Limber Pine (P. flexilis), 6. Beach Pine (P. contorta), 7. Lodgepole Pine (P. murrayana), 8. Western White Pine (P. monticola), 9. Knobcone Pine (P. attenuata), 10. Bristlecone Pine (P. longaeva), 11. Foxtail Pine (P. balfouriana), 12. Four-Leaf Pinyon (P. quadrifolia), 13. Two-Leaf Pinyon (P. edulis), 14. One-Leaf Pinyon (P. monophylla), 15. Ponderosa Pine (P. ponderosa), 16. Coulter Pine (P. coulteri), 17. Digger Pine (P. sabiniana), 18. Torrey Pine (P. torreyana), 19. Jeffrey Pine (P. jeffreyi), 20. Sugar Pine (P. lambertiana). Note: This image is scanned from a Kodachrome 35mm color transparency taken in 1974. Taxonomic changes have been made on some of these species. Note: In the Jepson Flora of California 2nd Edition (2012), Pinus remorata is now considered a synonym of P. muricata. Another species (left image) called the Washoe pine (P. washoensis), with cones similar to a miniature Jeffrey pine, is now recognized as a variety of the ponderosa pine (P. ponderosa). In addition, the beach and lodgepole pines are now recognized as subspecies of P. contorta, rather than separate species. This gives a grand total of 18 species, 7 subspecies and 3 varieties.

The traditional taxodium family (Taxodiaceae) contains ten genera and 16 species of cone-bearing trees native to North America, Asia and Tasmania. Because of their scale-like leaves, seed cones and other characteristics, some botanists have consolidated the Taxodiaceae with the cypress family (Cupressaceae). In fact, the seed cones of bald cypress (Taxodium) certainly resemble those of the true cypress (Cupressus). Leaves of the Cupressaceae are opposite in four ranks or whorled, while those of the Taxodiaceae are mostly alternate; however, vegetative characteristics are not reliable for differentiation between families. Modern taxonomists use DNA sequencing and computers to generate phylogenetic "trees" called cladograms. The protein-coding RBCL chloroplast gene is often used at the family level to show relationships between genera and species within a family. The results of these studies indicate that a number of genera formerly assigned to the Taxodiaceae now belong in the Cupressaceae. The principle exception is the genus Sciadopitys (Japanase umbella pine), which was found to be completely unlike the Cupressaceae, and is now placed in the monotypic family Sciadopityaceae. Much to the chagrin of some botanists, sweeping changes are being proposed in the field of conifer taxonomy in order to provide a consistent method of plant classification at the family level. Some drastic changes in the classification of traditional flowering plant families have also been proposed, including the placement of all duckweeds in the arum family (Araceae). If accepted by the botanical community, the incorporation of these changes into botany textbooks, floras, checklists and herbarium collections will be a formidable task.

Many economically important species belong to the taxodium family, including cultivated ornamentals and timber trees. They are dominant trees in several ecosystems, including temperate forests and swamps. Most of the species are evergreen, but some are deciduous and drop their leaves during the fall months. In addition, the most massive and tallest trees in the world belong to this remarkable plant family. Abundant fossil evidence of these magnificent trees dating back more than 100 million years has been found in north America. Some of today's species look remarkable similar to fossilized trees that lived when dinosaurs walked on the earth.