Drosera rotundifolia (Roundleaf Sundew)

Drosera rotundifolia, commonly known as the Roundleaf Sundew, is a small but fascinating carnivorous plant renowned for its unique method of trapping prey.

Drosera rotundifolia – Roundleaf Sundew: An In-depth Look

Drosera rotundifolia is characterized by its rosette of round, flat leaves covered in red, glandular hairs that secrete a sticky, dew-like substance. This substance glistens in the sunlight, attracting and trapping insects, which the plant then digests to supplement the poor mineral nutrition of its environment.

Native: This species is native to Europe, Asia, and North America and is commonly found in boggy, acidic environments where nutrient levels in the soil are low. It belongs to the sundew family (Droseraceae), a family of carnivorous flowering plants comprising approximately 180 species, including the popular Venus Fly Trap (Dionaea muscipula).

Plant Type and Habit: It is a carnivorous, herbaceous perennial with a rosette-forming habit. The plant is known for its carnivorous eating habits, using sticky leaves to capture insects

Size: The plant is quite small, typically reaching only 2 to 10 inches (5-25 cm) in height. The leaves spread out to around 4 to 6 inches (10-15 cm), forming a tight, ground-level rosette.

Flowers: Drosera rotundifolia produces small, white to pinkish flowers that grow on a single, slender, upright stem that rises above the leaf rosette. The bloom period is in the summer, typically from June to August, depending on the climate. After flowering, it produces tiny, capsule-like fruits that contain numerous minute seeds.

Foliage: The leaves are circular or kidney-shaped, hence the name “round-leaved.” They are small, less than an inch in diameter, forming a tight rosette pattern that hugs close to the ground. This compact growth habit helps the plant conserve moisture in its native boggy habitats.

Each leaf is covered with numerous tiny, hair-like structures known as tentacles. These tentacles are tipped with glandular heads that secrete a sticky, glistening dew-like substance called mucilage. This secretion is crucial for the plant’s insect-trapping mechanism. The color of the leaves can vary from bright green to deep red. The intensity of the red coloration is often a response to the plant’s light exposure—with more intense sunlight typically leading to a deeper red.

The mucilage is visually appealing to insects, which mistake it for drops of water or nectar. When an insect lands on the leaf, it becomes ensnared by the sticky secretion. The more the insect struggles, the more entangled it becomes. Sensing the trapped prey, the surrounding tentacles slowly bend towards the center of the leaf, further enveloping the insect. This movement allows the plant to maximize contact with the insect, facilitating the secretion of digestive enzymes that break down the prey to absorb nutrients.

The leaf’s surface is not only adapted for trapping insects but also for absorbing the digested nutrients efficiently. The leaves contain enzymes like proteases and phosphatases, which help digest proteins and phosphates from the prey’s body, allowing the plant to absorb nitrogen and other nutrients directly through the leaf’s surface. This is vital for the plant’s survival in nutrient-poor soils where it typically grows.

Hardiness: Roundleaf Sundew is surprisingly hardy, suitable for USDA zones 3-8. It survives freezing temperatures by dying back to the root crown in winter.

Uses: Primarily grown as a curiosity or specimen plant in carnivorous plant collections, it can also be used in bog gardens or terrariums due to its need for consistent moisture.

Toxicity: It is not toxic to humans or pets, making it safe to grow in home gardens where children and animals are present.

Invasiveness: Drosera rotundifolia is not considered invasive.

Benefits: Drosera rotundifolia is beneficial for controlling insect populations naturally, making it an eco-friendly pest management option. It’s also highly educational, demonstrating unique plant adaptations and carnivory, and adds intriguing aesthetic value to terrariums and bog gardens.

Roundleaf Sundew: How to Grow and Care

Light: Prefers full sun but can tolerate partial shade. Adequate sunlight is crucial for the development of the sticky dew on its leaves, which is essential for trapping insects. If grown indoors, a sunny windowsill or artificial grow lights can provide the necessary light.

Soil: Requires nutrient-poor, acidic soil. A mix of sphagnum peat moss and perlite or sand works well, mimicking its natural bog habitat.

Water: Keep the soil consistently moist during the growing season. Use distilled water, rainwater, or reverse osmosis water, as tap water can contain minerals that harm the plant. Employing a tray method, where water is kept in a tray under the pot, allows the plant to absorb moisture from the bottom and helps maintain the needed humidity. During the winter, plants enter a period of dormancy so keep just moist during the winter and do not stand the plants in water

Temperature: Best grown in cooler temperatures typical of its natural boggy environments. It can tolerate summer heat if kept moist but prefers a range of 50-70°F (10-21°C).

Humidity: Requires high humidity to thrive. In dry indoor environments, a humidity tray or frequent misting can help meet its humidity needs.

Fertilizer: Avoid fertilizing as this can overwhelm and kill the plant due to its adaptation to nutrient-poor soils. As a carnivorous plant, Drosera rotundifolia obtains much of its nutrition from insects. If grown indoors where insect availability is low, you can occasionally feed it small insects like fruit flies.

Pruning: Produces small, white flowers on tall stalks during the summer. While the flowers are attractive, allowing the plant to flower can divert energy away from leaf production. You may choose to snip flower stalks to conserve the plant’s energy.

Propagation: Propagate by seed as soon as ripe or by division of clumps after flowering. Leaf cuttings during the growing season and root cuttings taken when dormant are alternative methods of propagation

Roundleaf Sundew: Common Problems

The Roundleaf Sundew is a relatively robust carnivorous plant, but like all plants, it can experience some issues, particularly when its specific growing conditions are not met.

Insufficient Light

• Symptoms: Lack of dew production on the tentacles, poor coloration, and elongated, weak growth.
• Solution: Ensure the plant receives several hours of direct sunlight daily. If growing indoors, consider using a grow light to supplement natural light.

Poor Water Quality

• Symptoms: Brown tips on leaves, overall decline in health.
• Solution: Use distilled water, rainwater, or reverse osmosis water for watering. Tap water can contain minerals harmful to the plant due to its sensitivity to dissolved solids.

Incorrect Soil Medium

• Symptoms: Poor growth or root rot.
• Solution: Use a soil mix specifically designed for carnivorous plants, typically sphagnum peat moss mixed with sand or perlite. Avoid regular potting soils or any soil containing fertilizers.

Overwatering

• Symptoms: Yellowing leaves, root rot.
• Solution: Although the soil should be kept consistently moist, ensure it is not waterlogged. Provide adequate drainage and consider the tray method where the plant can absorb water from below as needed.

Low Humidity

• Symptoms: Drying of leaves, reduced dew production.
• Solution: Maintain high humidity around the plant, especially if grown indoors. Use a humidity tray or a room humidifier, or grow the plant in a terrarium to keep the surrounding air moist.

Pests

• Common Pests: Aphids, spider mites, and fungus gnats can attack the plant, especially under indoor conditions.
• Solution: Treat with a diluted pesticide or remove pests by hand. Do not use a soap-based insecticide.

Nutrient Overload

• Symptoms: Burnt-looking leaves, poor growth.
• Solution: Avoid fertilizing as Drosera rotundifolia gains necessary nutrients from the insects it captures. Excessive nutrients can overwhelm and kill the plant.

Flowering Exhaustion

• Symptoms: Plant appears weakened or stressed during or after flowering.
• Solution: While the flowers are attractive, allowing the plant to flower can drain its resources. You can snip flower stalks early to conserve energy for leaf production.