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).

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. 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. The results of these studies indicate that a number of genera formerly assigned to the Taxodiaceae now belong in the Cupressaceae. The protein-coding RBCL chloroplast gene is often used at the family level to show relationships between genera and species within a family. Modern taxonomists use DNA sequencing and computers to generate phylogenetic 'trees' called cladograms.

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. In fact, the seed cones of bald cypress ( Taxodium) certainly resemble those of the true cypress ( Cupressus). Because of their scale-like leaves, seed cones and other characteristics, some botanists have consolidated the Taxodiaceae with the cypress family (Cupressaceae). T he traditional taxodium family (Taxodiaceae) contains ten genera and 16 species of cone-bearing trees native to North America, Asia and Tasmania.

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Metasequoia seeds