Montana Field Guide

PLANTS: Perennial herbs with basal leaves and an unbranched leafless stem that is 8-25 cm high. Plants arise from a central rootcrown. Source: Lesica et al. 2012.

LEAVES: The leaves are ascending to prostrate, all basal and borne on petioles 2-6 cm long. They have narrowly oblong blades that are 1-3 cm long and 3-5 mm wide and covered on the upper surfaces with reddish-purple, stalked glands that trap insects. Source: Lesica et al. 2012.

INFLORECENCE: A 1-sided, nodding, 2 to 7 flowered, raceme-like cyme. Flowers are perfect and have 5 white petals. Source: Lesica et al. 2012.

The specific epithet anglica translates from Latin directly to its common name “English.” The species was first described on record in England in 1778 and the specimen can now be found in the herbarium of the Linnean Society of London (Wolf et al. 2006). Drosera is derived from the Greek drosos meaning “dewdrops” referring to the dewdrop-like glands on the leaves (Giblin et al. [eds.] 2018).

Flowering late June-July, fruiting July-August.

Montana has 3 native species of Drosera. All species are insectivorous, perennial herbs that trap prey in on their sticky, gland-tipped leaf hairs. The inflorescences of all species are 1-sided, nodding, raceme-like cymes that consist of regular, white flowers. A hand lens or microscope is required to measure the seeds.

Note that small, young basal rosettes are not particularly reliable or helpful for species identification (Rice 2019).

English Sundew - Drosera anglica, native, SOC
*Size: Mature plants are 8-25 cm tall.
*Leaves: Blades are narrowly oblong, ascending, and 10-25 mm long with a 2-6 cm long petiole.
*Capsules: 3-6 mm long.
*Seeds: Pointed at the tip and 1-1.5 mm long.
*Flowers: Mature flowers have petals that are 4-8 mm long, a calyx that is 4-5 mm long, and 4 to 5 styles.
*Anthers: Yellow.

Roundleaf Sundew - Drosera rotundifolia, native, potential SOC
*Size: Mature plants are 3-20 cm tall.
*Leaves: Blades are orbicular, spreading, and 4-12 mm long with a 1-3 cm long petiole.
*Capsules: 3-5 mm long.
*Seeds: Elongate and flat at the tip and about 1.5 mm long.
*Flowers: Mature flowers have petals that are about 6 mm long, a calyx that is just shorter, and usually 3 styles.
*Anthers: White.

Slenderleaf Sundew - Drosera linearis, native, SOC
*Size: Mature plants up to 15 cm tall.
*Leaves: Blades are linear, ascending, and 2-5 cm long.
*Capsules: 4-5 mm long.
*Seeds: Round at the tip and less than 1 mm long.
*Flowers: Mature flowers have petals that are 4-8 mm long, a calyx that is 4-5 mm long, and 4 to 5 styles.
*Anthers: Bright orange.

English Sundew grow with Spaghnum moss in wet, organic soils of fens in the montane zone (Lesica et al. 2012). Plants may also occur in grass or sedge dominated seeps (Rice 2019).

Drosera anglica traps and digests primarily insects from the Dipteran and Coleopteran orders as well as many other arthropods (Wolf et al. 2006).

HYBRIDIZATION
Drosera anglica is most likely originated as a sterile hybrid of D. linearis x D. rotundifolia (Wood 1955; Hoyo et al. 2015). The species later became fertile possibly due to a natural chromosome doubling event (Rice 2019). Where their ranges overlap, D. anglica and D. rotundifolia may also hybridize to form the resulting hybrid Drosera x obovata (Wood 1955).

ASSOCIATED SPECIES
English Sundew typically grows on floating mats covered with Sphagnum mosses. It is also closely associated with many Carex species including C. limosa and C. lasiocarpa and herbaceous dicots such as Menyanthes trifoliata. Other rare species found only in Sphagnum fens can typically be found in association with Drosera anglica as well. Source: Wolf et al. 2006.

PLANT COMPETITION
Because of its smaller stature, Drosera anglica is often overtaken by Sphagnum mosses and outcompeted for sunlight. Consequently, access to sunlight is a significant limiting factor in the distribution of English Sundew (Wolf et al. 2006).

Competition with other carnivorous plants and ants for prey is also limiting for English Sundew (Thum 1986; Gibson 1991). Ants have been observed stealing prey insects off the leaves of Drosera species (Thum 1989).

PREY CAPTURE
Prey insects are initially lured to plants by their brilliant red gland stalks (Wolf et al. 2006). This pigmentation may vary due to environmental effects such as sun exposure and inundation (Rice 2019). After landing or climbing onto the leaves, prey get stuck to the longer, trapping glands on the margins of the leaves which hold them in place while the shorter glands secrete digestive enzymes (Lloyd 1942). A bending of the leaf petiole to fold the leaf over itself also assists in keeping prey in place once entrapment has occurred (Darwin 1897).

All three species of Drosera can reproduce both sexually and vegetatively (Hoyo et al. 2015; Murza et al. 2003). Sexual reproduction is almost exclusively accomplished through self-pollination leading to most offspring being genetically identical to parent plants whether they reproduce sexually or vegetatively (Wolf et al. 2006).

English Sundew reproduces vegetatively by producing new raments that sprout from the plants (Hoyo et al. 2015). This occurs when leaf buds separate and form plantlets or when axillary buds form beneath rosettes and then detach when the connecting stem decays (Wolf et al. 2006). Both methods result in a new, clonal individual.

FRUITS AND SEEDS
Fruits are many-seeded capsules that are 3-6 mm long (Lesica et al. 2012). Seeds are 1-1.5 mm long, longitudinally striate and not flattened at the tips (Giblin et al. [eds.] 2018). Upon closer inspection the striations consist of tiny window-shaped indentations arranged in rows (Rice 2019).

FLOWERS
Each flower has a 5-lobed calyx that is 5-6 mm long and 5 separate, oblong, white petals that are longer than the calyx. There are 5 stamens and 4-5 styles, which are divided more than half their length (Lesica et al. 2012). The flowers of English Sundew are self-pollinating and therefore, almost never found open (Wolf et al. 2006).

LIFE CYCLE [Wolf et al. 2006]
English Sundew has four main life stages including seed, seedling, mature plant and vegetative propagule. During this time, it may also go through 2 dormant life stages including seed bank and overwintering buds. First year seedlings do not reproduce.

The most effective way to preserve populations of Drosera anglica is to ensure that the water regimes of its primary habitat remain unaltered (Wolf et al. 2006). Better informed management decisions of D. anglica populations can be made by taking inventory of watersheds where colonized fens are present. Activities such as logging, groundwater pumping, grazing, and recreation should be closely monitored for their effects on nutrient levels.

In areas across its range hydrologic alterations to the fens has been identified as a primary threat (Wolf et al. 2006). Drosera species require very specific ground water conditions for plants to maintain their ideal nutrient levels. Being adapted to nutrient poor environments makes them extremely sensitive to nutrient level increases. When this is disrupted in any way, proper ecosystem functioning may be inhibited.

STATE THREAT SCORE REASON
Reported threats to Montana's populations of English Sundew include populations located where recreation-related disruption or non-native species competition has negative impacts. One population is located near the base area of a ski resort, and future expansion of existing facilities are likely. Some populations occur in the vicinity of expanding non-native plant populations that have potential to out-compete small-statured English Sundew for light and soil nutrients. Trampling by recreationalists is expected where English Sundew populations are frequently visited by people (MTNHP Threat Assessment 2021).