Sarracenia purpurea subsp. venosa (Raf.) Wherry

Where it comes from

The south-eastern coastal plain — Kew’s regions are North Carolina, South Carolina and Georgia.¹ Bogs and wet savanna, in full sun, in soil with nothing in it.

Be careful with the cold-hardiness claim attached to this plant. Sarracenia purpurea as a species reaches Labrador and the Northwest Territories, and gets called the hardiest pitcher plant on that basis. This subspecies is a zone 6a-8b plant,² and in zone 5 and colder the only one that reliably overwinters outdoors is subsp. purpurea.³ The species’ range is not this plant’s range.

Naming and description

Worth pinning down, because the label and the accepted name differ in rank. Kew accepts Sarracenia purpurea subsp. venosa (Raf.) Wherry, published in Bartonia 15: 3 (1933).¹ The familiar “var. venosa” is the same plant at a different rank — a real botanical name, not a cultivar, which is a relief after the last two groups.⁴ The two authorities disagree about who published the varietal combination and when, and IPNI is the one to follow on a question of pure nomenclature.⁴⁵

Two neighbouring names have moved, which matters if you are reading older sources: var. montana has been sunk into subsp. purpurea, and var. burkii has been raised to a species of its own, Sarracenia rosea.⁶⁷ So Gulf Coast plants sold as “purpurea” are usually not this species at all, and are a zone less hardy.

The pitchers are squat, decumbent and veined red, with an erect lid that stands clear of the mouth rather than roofing it.

Fun facts

• Its pitchers are full of rainwater, not digestive fluid, and that is the whole design. Because the lid does not cover the opening, the pitchers fill from the sky.⁸⁹ This is the one Sarracenia you can and should top up: ICPS says the purpurea group like water added to their pitchers.³
• It may not digest its own prey at all — something else does it. A 2019 survey of nine Sarracenia taxa found protease lacking in this subspecies by name, and suggested enzyme production is replaced by degradation carried out by the inquiline fauna living in the fluid.¹⁰ An earlier study did find enzymes, but only inducible ones that switch on with prey and stop within two weeks without it.¹¹ The honest version is that this is unsettled and interesting — and that NC State’s flat statement that the pool contains insect-digesting enzymes is the weakest of the three positions.¹²¹³
• Each pitcher is a five-level food web, and it has been used to model ecological collapse. Bacteria, protozoa, a rotifer, a midge, and the mosquito Wyeomyia smithii live in the fluid;⁸ the mosquito is a keystone predator that raises bacterial diversity by preying on the grazers above.¹⁴ Researchers have used these pitchers as a physical model of eutrophication tipping points, and measured the crossing from aerobic to anaerobic at about 45 hours once prey loading passed 0.5 mg per millilitre per day.⁸ Which is also a good argument against stuffing yours with insects.
• Prey supplies between a tenth and four fifths of its nutrients, roots supply about five per cent, and the plant can take up intact amino acids within hours — skipping the mineralisation step entirely.⁹
• It does not eat its pollinators, and the mechanism is simply geometry. The flower scape is held at or above pitcher height. In one study, floral visitors — two bee species and a fly that is itself a pitcher inquiline — were never collected as prey.¹⁵