Round-leaved Sundew

Drosera rotundifolia has the widest distribution of any sundew species, with a circumboreal range spanning the Northern Hemisphere.

• Native across northern and central Europe, throughout much of Asia (including Siberia, Japan, and parts of China), and across Canada and the northern United States
• Found from sea level to elevations exceeding 2,000 meters in some mountainous regions
• Its range extends as far south as the Appalachian Mountains in the United States and the Pyrenees in Europe
• The genus Drosera is believed to have originated in the Southern Hemisphere (Africa or Australia), with D. rotundifolia representing a lineage that migrated northward

Fossil pollen records of the Droseraceae family date back to the Eocene epoch (~40 million years ago), suggesting a long evolutionary history of carnivory in this group.

The Round-leaved Sundew is a small, rosette-forming, perennial herbaceous carnivorous plant, typically growing only 5 to 25 cm in total height.

Leaves:
• Arranged in a basal rosette lying flat or nearly flat against the ground (~3–5 cm in diameter)
• Leaf blades (laminae) are round to broadly obovate, measuring 4–11 mm in diameter
• Each lamina sits atop a narrow, elongated petiole (~1–5 cm long), giving the rosette a radiating star-like appearance
• Both the upper surface and margins of each lamina bear numerous stalked glandular trichomes (tentacles), each tipped with a glistening droplet of clear, viscous mucilage (~1–2 mm long)
• Tentacles are reddish-green and slowly bend inward when stimulated by prey contact (thigmotropism), a process that can take minutes to hours

Flowers:
• Produced on a slender, erect scape (flowering stalk) 5–25 cm tall
• Flowers are small (~4–8 mm across), white, with 5 petals, 5 sepals, 5 stamens, and a 3-parted stigma
• Flowers open one at a time, typically only in direct sunlight, and are self-pollinating (autogamous)
• Blooming period: June to September in the Northern Hemisphere

Fruit & Seeds:
• Capsule fruit containing numerous minute, elongated seeds (~0.5–1.2 mm)
• Seeds dispersed by wind and water

Roots:
• Root system is weak and fibrous, serving primarily for anchorage rather than nutrient uptake
• Nutrient absorption occurs mainly through carnivory (digesting trapped prey)

The Round-leaved Sundew is an obligate wetland species, restricted to acidic, nutrient-poor (oligotrophic) habitats.

Habitat:
• Sphagnum bogs, peatlands, and fens
• Wet, acidic seeps and stream margins
• Damp sand flats and peaty lake shores
• Often grows intermixed with Sphagnum mosses, which help maintain the acidic, waterlogged conditions it requires

Soil & Substrate:
• Requires perpetually moist to waterlogged, highly acidic substrates (pH 3.0–5.5)
• Extremely low in available nitrogen and phosphorus — precisely the conditions that drove the evolution of carnivory

Carnivory Mechanism:
• Tentacle-tipped mucilage droplets attract insects through glistening light refraction and a sugary scent
• Upon contact, prey become stuck in the viscous secretion
• Adjacent tentacles slowly bend toward the prey (thigmotropic response), maximizing contact
• The leaf blade itself may partially curl around the prey in some cases
• Glands secrete digestive enzymes (proteases, esterases, peroxidases) that break down soft tissues over 1–3 days
• Absorbed nutrients (particularly nitrogen and phosphorus) are transported to support growth and reproduction
• The indigestible exoskeleton is left behind after the leaf reopens

Prey:
• Primarily small flying insects such as gnats, midges, fruit flies, and small mosquitoes
• Occasionally captures ants, springtails, and even small damselflies

Reproduction:
• Primarily by seed; also capable of forming new rosettes from root buds in favorable conditions
• Some populations produce bulb-like hibernacula (winter buds) in colder climates — compact clusters of tightly furled leaves that survive freezing temperatures and unfurl in spring

• Drosera rotundifolia is listed as Least Concern (LC) globally on the IUCN Red List
• However, it is declining or locally threatened in many regions due to habitat loss
• Major threats include: drainage of peatlands, peat extraction, agricultural conversion, eutrophication (nutrient runoff), and climate change drying out bogs
• Protected under national legislation in several European countries (e.g., listed as a protected species in Switzerland and parts of Germany)
• In the United Kingdom, it has declined significantly due to widespread loss of lowland bogs — an estimated 94% of lowland raised bogs have been destroyed
• Conservation efforts focus on bog restoration, rewetting of drained peatlands, and legal protection of remaining wetland habitats

• Drosera rotundifolia is considered non-toxic to humans and pets
• The mucilage contains plumbagin (a naphthoquinone compound), which can cause mild skin irritation or redness in sensitive individuals with prolonged contact
• Historically used in herbal medicine in small doses; excessive internal consumption may cause nausea and gastrointestinal irritation
• Plumbagin has demonstrated antimicrobial and anti-inflammatory properties in laboratory studies

The Round-leaved Sundew can be cultivated at home by hobbyists, though it requires specific conditions that mimic its natural bog habitat.

Light:
• Full sun to bright indirect light; needs at least 4–6 hours of direct sunlight daily for optimal tentacle coloration and vigor
• Insufficient light causes pale, elongated growth and reduced mucilage production

Water:
• Must be kept constantly wet — the pot should sit in a tray of standing water at all times
• Use only distilled water, reverse osmosis water, or collected rainwater
• Tap water, even if 'soft,' typically contains dissolved minerals that will kill the plant over time

Soil:
• Use nutrient-poor, acidic growing media — never standard potting soil or fertilizer-enriched mixes
• Recommended: a 1:1 mix of sphagnum peat moss and perlite, or pure long-fiber sphagnum moss
• The pot should be deep enough to accommodate the root system and allow for standing water (~10–15 cm deep)

Temperature:
• Hardy in USDA zones 3–8; tolerates freezing winter temperatures
• In colder climates, the plant forms hibernacula and dies back to ground level in winter, resprouting in spring
• Some growers keep plants in a refrigerator during dormancy (0–5°C for 3–4 months)

Feeding:
• Does not require manual feeding if grown outdoors (it will catch its own prey)
• Indoor plants may benefit from an occasional small insect or a tiny pinch of dried bloodworms (fish food) applied to a leaf

Propagation:
• By seed (sown on moist sphagnum, kept warm and bright, germinates in 2–4 weeks)
• By leaf cuttings placed on moist sphagnum
• By root cuttings in late winter

Common Problems:
• Blackening of leaves → often natural aging; remove dead leaves to prevent mold
• No mucilage production → insufficient light or mineral-contaminated water
• Fungal infection → improve air circulation, avoid overcrowding
• Failure to form hibernaculum → may need a genuine cold dormancy period

• Ornamental cultivation by carnivorous plant enthusiasts worldwide
• Historically used in European folk medicine as a cough suppressant and anti-inflammatory remedy
• Sundew extracts were traditionally used to treat coughs, asthma, and whooping cough — the common name 'sundew' may derive from the Latin 'ros solis' ('dew of the sun'), referencing its historical medicinal use
• Plumbagin, a bioactive compound found in D. rotundifolia, is the subject of ongoing pharmacological research for its potential anticancer, antimicrobial, and anti-inflammatory properties
• Used as a bioindicator species for assessing the health of bog and wetland ecosystems
• Occasionally used in botanical education to demonstrate plant carnivory and evolutionary adaptation