Darlingtonia californica

A twisted pitcher with a forked tongue

Each adult pitcher rises as a tube that twists through 90 to 270 degrees and swells at the top into a rounded dome. The entrance sits under the dome and faces the ground, and from its rim hangs a flattened, two-lobed appendage that Flora of North America calls fishtail-shaped ^[7]. The dome is dotted with white, translucent patches (areolae). Pitchers usually measure 40 to 60 cm and occasionally reach 1 m ^[2].

The flowers are just as unusual. They hang from stalks 50 to 100 cm tall, with yellow-green sepals 3 to 6 cm long and reddish brown petals whose notches line up to leave five small openings into the flower ^{[2, 7]}. Flowering runs from mid-April into July, but the buds are formed the previous fall and overwinter protected by bracts ^[2]. The ICPS reports that small sweat bees pollinate them in the wild ^[3].

Young plants look different again. Juvenile pitchers are long tubes with a narrow, tongue-like tip that often curves toward the ground, while adult pitchers carry the dome and fishtail. In a 2014 CPN article John Brittnacher showed that seedlings make a flat, gland-free leaf right after the seed leaves, before any pitcher, which he interprets as an ancestral, non-carnivorous leaf ^[8].

How the trap works, and what the “tongue” may not do

The ICPS classes Darlingtonia as a lobster-pot trap. The entrance is easy to find from outside but dark from inside, while light pours in through the areolae, so insects that move toward light tend to miss the exit and fall down the tube ^[9].

The fishtail appendage has long been assumed to lure prey to the entrance. A field experiment by David Armitage questions that: removing the appendages before the pitchers opened did not reduce the biomass or change the kinds of prey caught, either on single leaves or across whole populations. Appendages on shaded plants held more chlorophyll than those in full sun ^[10]. In a second study he found that bacteria cultured from pitchers produce fluid with the same physical properties as natural pitcher fluid, and that these properties help keep insects from escaping ^[11].

Cold water over serpentine

The cobra lily grows in marshy streams, seeps and bogs from sea level to 2,600 m ^[2]. The ICPS guide stresses one shared feature: almost every wild site has cold spring water flowing through the soil. Plants grow in exposures from hot, south-facing lowlands to cool north-facing mountain slopes, and in full sun as well as dense shade. Most sites are on serpentine, which the ICPS guide attributes to the plant tolerating minerals that are toxic to its competitors rather than needing them ^[3]. In a five-year study after a 2002 fire burned about 202,000 ha of the Klamath Mountains, burned fens had less plant cover for two years but proved highly resilient overall ^[12].

How the seeds reach new seeps is debated. Flora of North America says the long projections on the seeds let them float ^[2]. A 2015 CPN article proposes that animals, bears in particular, also carry seeds in their fur between widely separated wet sites, noting that most seeds stay in the upturned capsules until something brushes the stalks. The author calls his evidence largely circumstantial, and microscope images showed the seed bristles lack barbs or hooks ^[13].

Conservation status

IUCN assessed the species for the Red List in 2000; see the assessment for its category ^[14]. NatureServe ranks it G3G4 (vulnerable to apparently secure), describes its range as narrow and its populations as scattered though locally plentiful, and names habitat destruction and collecting for the domestic and international horticultural trade as threats ^[5]. Flora of North America adds road building, drainage, logging, ranching, drought and “unscrupulous collectors” ^[2]. Darlingtonia was in CITES Appendix II from 1981 until it was deleted from the Appendices in 2000 ^[6]. Seed and plants for growing should come from cultivated stock.

Keeping the roots cold

Heat at the roots is what kills cultivated plants. The ICPS guide says the soil must stay below 27 °C (80 °F) for long-term success, although some clones tolerate more heat, and that collapse usually begins in hot weather at the growth points nearest the pot wall ^[3]. Its practical advice:

• Water from the top regularly, early in the morning when the water is coolest.
• In hot spells, some growers set ice cubes made from distilled or reverse-osmosis water on the soil each day, pump in chilled water, or float pots in deep trays.
• Use large pots, which hold temperature better, or sink them in the ground in shade.
• Choose a mix that holds water but stays airy; there is no evidence that serpentine gravel helps.

All of these points come from the ICPS guide ^[3]. Soil fertilizer does not appear to help, and the guide notes that plants from high elevations are more cold-hardy but less heat-tolerant ^[3]. The water and soil guides cover the basics shared with other carnivorous plants.

Seed origin matters too. The ICPS guide notes that populations around Gasquet, California show unusual variety in form, color and size, and suggests that moderate-elevation inland populations, such as many in Josephine County, Oregon, may handle heat better ^[3]. The anthocyanin-free cultivar ‘Othello’ came from Nevada County, California, at 1,750 m ^[3].

Propagation

Seed needs four weeks of damp cold stratification, for example in a bag with moist chopped sphagnum in the refrigerator, and seedlings then spend two to four years in their first pot ^[3]; see cold stratification and sowing seeds. Vegetative methods are faster. Plantlets that form at the ends of stolons can be cut off and potted in live sphagnum, which the ICPS describes as very reliable. Leaf pullings, taken with a little rhizome tissue and kept cool and humid, may root in a couple of months and produce a plantlet in about four to six months ^[15]. Winter care follows the pattern described in the dormancy guide.