Carnivorous Plants of New England

What's a Carnivorous Plant?

Carnivorous plants are photosynthetic plants that are found in wetlands or aquatic environments where the biologically available forms of one or more nutrients are in scarce supply. Due to the low availability of nutrients, carnivorous plants are generally unable to uptake enough dissolved nutrients from the soil or water to be able to grow robustly. To compensate for the paucity of available nutrients in the soil and/or water where they grow, carnivorous plants have evolved traps to capture small animals for food. In most cases the traps are modified leaves, or modified parts of leaves. The captured prey are digested in the traps and the nutrients that are released are absorbed and utilized by the plant to support growth and development.

Carnivory has evolved in flowering plants on at least 10 independent occasions (Fleischmann et al. 2018).

Carnivorous Plants Found in New England

Five types of carnivorous plants are found in New England — sundews, waterwheel plants, pitcher plants, bladderworts, and butterworts. Sundews and pitcher plants occur in peatlands; waterwheel plants and bladderworts are aquatic species found in a range of freshwater environments; and butterworts occur in wet, rocky, boreal and subalpine habitats. All of the carnivorous plants found in New England are flowering plants from the eudicot clade. They are all native to New England except for waterwheel plant, which was introduced and is considered invasive here.

Carnivorous plants of New England are listed below by family.

Droseraceae (Sundew Family)

Drosera (Sundews)

Sundews have modified leaves with sticky mucilage-tipped tentacle hairs. Insects coming into contact with the tentacle hairs become stuck. The prey’s repeated movements trigger movement of the tentacle hairs, which begin encompassing the prey until the prey becomes enfolded in the leaf. The tentacle hairs release an anesthetic and digestive enzymes and the prey is slowly dissolved and absorbed by the plant. The following five species of sundew occur in New England:

• Drosera anglica (English sundew)
• Drosera filiformis (thread-leaved sundew)
• Drosera intermedia (spatulate-leaved sundew)
• Drosera linearis (slender-leaved sundew)
• Drosera rotundifolia (round-leaved sundew)

Aldrovanda (Waterwheel plants)

Like venus flytraps, waterwheel plants have modified leaves that form snap-traps for catching prey. Each trap consists of a single leaf with two lobes. The lobes are located on each side of the midrib of the leaf, with the midrib functioning as the joint or hinge of the trap. Sensitive trigger hairs are located on the inside of the trap. When prey come into contact with the trigger hairs, the two lobes snap together. The edge of each lobe has an infolded rim and inward-oriented teeth to help contain the prey within the trap. A number of glands are located inside the trap; these produce and secrete enzymes to digest prey and are involved in the absorption of the nutrients from the dissolved prey. The traps (trap leaves) occur in whorls along the stem of the plant, with each whorl consisting of five to nine traps.

One species of waterwheel plant is found in New England. Although regarded as invasive in the northeastern United States, it is listed as globally endangered on the IUCN Red List of Threatened Species (Cross and Adamec 2020).

• Aldrovanda vesiculosa (waterwheel plant)

Sarraceniaceae (Pitcher Plant Family)

Sarracenia (North American pitcher plants)

Pitcher plants trap insects in pitcher-shaped leaves. Only one species of pitcher plant occurs in New England: the purple pitcher plant (Sarracenia purpurea). The “pitchers” contain rainwater and support a tiny community of aquatic organisms including, among other things, bacteria, rotifers, ciliates, mites, flagellates, fungi, and larvae of midge, mosquito and flesh fly species. To lure prey into the trap, pitcher plants have nectar glands on the flared opening of the pitcher leaf (sometimes referred to as a "hood" or "lid"). In addition to the hood, nectar glands are found in the vicinity of the lip/rim of the pitcher, extending into the top part of the pitcher. The nectar that is secreted contains both sugar and amino acids. Downward pointing hairs on the hood of the pitcher may help direct prey into the water-filled trap. Insects that fall into and drown in the trap are broken down, digested and partially consumed by the aquatic community within the pitcher. Nutrients released into the pitcher are taken up by the plant. All digestive enzymes in the pitcher are believed to be produced by microoorganisms in the pitcher, and not by the pitcher plant.

• Sarracenia purpurea (purple pitcher plant)

Lentibulariaceae (Bladderwort Family)

Utricularia (Bladderworts)

Leaves of bladderworts contain small bladders that trap tiny aquatic animals. The bladders are deflated until sensitive hairs outside of the bladders are triggered by the movement of a zooplankter or other prey. Once triggered, the bladders open, drawing in water and prey before snapping shut. The prey is then digested by enzymes and bacteria inside the bladder and the byproducts are absorbed by the plant. The following 12 species of bladderwort occur in New England:

• Utricularia cornuta (horned bladderwort)
• Utricularia geminiscapa (mixed bladderwort)
• Utricularia gibba (humped bladderwort)
• Utricularia inflata (swollen bladderwort)
• Utricularia intermedia (flat-leaved bladderwort)
• Utricularia minor (lesser bladderwort)
• Utricularia purpurea (purple bladderwort)
• Utricularia radiata (floating bladderwort)
• Utricularia resupinata (resupinate bladderwort)
• Utricularia striata (striped bladderwort)
• Utricularia subulata (slender bladderwort)
• Utricularia vulgaris (common bladderwort)

Pinguicula (Butterworts)

Butterworts have sticky, greasy leaves that they use to trap and digest insects and other small prey. The leaves have two types of glands: stalked glands and sessile glands. The stalked glands contain droplets of sticky muco-polysaccharides, which are used to trap the prey. These glands also release amylases— enzymes that break down starch into sugars. When triggered by the presence of appropriate prey, the sessile glands secrete digestive enzymes, including proteases (for breaking down proteins). The prey is digested on the leaf surface. Following digestion, the sessile glands are apparently involved in the resorption of the digestion products into the leaf.

One species of butterwort is found in New England:

• Pinguicula vulgaris(common butterwort)