Flora of North America species comparison

Genera 3, species 22 (2 genera, 12 species in the flora).

The North American pitcher plants are a fascinating group of carnivorous plants with leaves modified into tubular pitfall traps that attract, catch, and digest small invertebrate prey. The pitchers have no moving parts but contain downward-pointing hairs on the interior surfaces. The hoods keep out rainwater and prevent flying prey from escaping; only Sarracenia purpurea and S. rosea normally contain rainwater inside the pitchers.

Darlingtonia californica is found scattered in the Pacific Northwest (California and Oregon). Sarracenia occurs mainly in the southeastern United States, with one species (S. purpurea) occurring northward and westward across Canada to British Columbia, and naturalized in Switzerland, the British Isles, and Japan. Heliamphora Bentham, a tropical genus with about 15 species, is endemic to the Guayana Highlands of northern Brazil, western Guyana, and southern Venezuela. All species are characteristic of moist-to-wet, open, sunny, low-nutrient, acidic habitats.

The evolutionary origins and relationships of the Sarraceniaceae are obscure, and there is only one (highly questionable) fossil record (Li H. Q. 2005). Molecular data suggest Ericalean affinities (R. J. Bayer et al. 1996). Some authors have suggested that Heliamphora is primitive in the family (B. Maguire 1978) because its pitcher structure is less complex. All three genera have specializations, and their pitcher morphologies are likely affected by adaptations to their wet environments and carnivorous habits. Because we cannot reliably ascertain which taxa are primitive in this family, the genera and species are presented in alphabetic order.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species 11 (11 in the flora).

Sarracenia species are among the most beautiful and intriguing plants in the world; we know very little of their phylogenetic origins and affinities. They have been important ornamental plants since the early nineteenth century. Artificial hybrids were made in England in the late nineteenth century (J. H. Veitch 1906). Today, all species and some natural and man-made hybrids are widely grown by hobbyists and botanical gardens around the world.

In Sarracenia, recognition of some species is often based less on flower traits than on subtle characteristics of the pitcher leaves. Species determinations must be done using the largest, most mature pitchers from healthy plants growing in moist soil and full sun. Pitchers from heavily shaded or dry sites may be smaller, flat like phyllodial leaves, or weak and decumbent. The keys here are based on typical pitcher traits. It is best to examine multiple leaves from multiple plants in a population and to note presence or absence of phyllodia. In addition, distinctly different types and sizes of leaves may be produced throughout the growing season, and these are noted in the species descriptions.

The pitchers of Sarracenia may be produced before, during, or after the emergence of the flowers; pitcher phenology can be useful for species identification. Flower buds are initiated during late summer, remaining dormant until the following spring. Sometimes, these flowers may bloom out of season in late summer or fall. The pitchers of certain species are marcescent, withering in the winter but not abscising. Other species have persistent pitchers.

Sarracenia species hybridize readily. The hybrids are fertile and may backcross and interbreed to form hybrid swarms. The swarms are legendary along the Gulf Coast (and may have increased due to habitat disturbance), leading to great confusion in species identification. At the end of this treatment, we have enumerated the known naturally occurring F1 hybrids.

Nearly every species of Sarracenia has been found in the wild in an anthocyanin-free form, lacking the normal red coloration in the flowers or pitchers. One of these all-yellow variants from the Northeast is well known and has been named S. purpurea forma heterophylla (Eaton)Fernald, the epithet referring to sun and shade pitchers of different morphologies on the type specimen. Most other color variants have not been named. Amateur collectors frequently refer to yellow variants of any taxon as the “heterophylla form.” These plants are very rare and virtually unrepresented in herbaria.

Sarracenia habitats in the Southeast are maintained by fire. This is especially true in the pine flatwoods and savannas. Without frequent fires, these open, sunny, acidic, low-nutrient habitats quickly become dense thickets of woody or grassy vegetation. The pitcher plants will invariably be shaded, and appear weakened and atypical. Most of them will survive to some degree and will be rejuvenated after a fire.

We realize that some of our decisions to recognize taxa below the rank of species are controversial. Our treatment reflects our thoughts after decades of study and observation in the wild and the common garden. Most of the difficult-to-distinguish taxa have allopatric distributions, separating them from their similar relatives—a first step in making it possible to recognize them as separate entities. Knowledge of the exact geographic origin of specimens in question will be useful, especially with members of the Sarracenia purpurea and S. rubra complexes.

(Discussion copyrighted by Flora of North America; reprinted with permission.)