Drosera erythrorhiza, commonly known as the red ink sundew, is a carnivorous plant. This distinctive species belongs to the group of tuberous sundews, known for their unusual life cycle adapted to specific seasonal climates. Its rosetted leaves, adorned with sticky, dew-like tentacles, are effective traps for insects, allowing it to supplement its nutrient intake from the soil.
Understanding Drosera erythrorhiza
Drosera erythrorhiza is classified as a tuberous sundew, named for its specialized underground storage organ, the tuber. This tuber, often pea-sized, stores energy and nutrients, enabling the plant to survive harsh environmental conditions by retreating underground during drought and heat.
This species is native to Western Australia, where its natural habitat experiences a Mediterranean-like climate with cool, moist winters and hot, dry summers. This seasonal pattern dictates the plant’s growth and dormancy cycles; it actively grows during cooler, wetter months and retreats into its tuber during the dry summer. During its active growth, Drosera erythrorhiza forms a flat rosette of broad, round leaves, typically 3-8 cm in diameter, which lie close to the ground. These leaves are covered in glistening, glandular hairs that trap insects, contributing to the plant’s “red ink” common name due to the reddish tint some plants display in strong light.
Cultivation and Care
Cultivating Drosera erythrorhiza requires understanding its specific needs during its active growth phase, which typically occurs in cooler, wetter months. Providing the right conditions helps ensure robust growth and prepares the plant for its necessary dormancy.
Light
Drosera erythrorhiza thrives in intense, direct sunlight. Insufficient light can lead to stunted growth, reduced dew production on the leaves, and a lack of the characteristic reddish coloration. If growing indoors, powerful artificial grow lights are often necessary.
Watering
Consistent moisture is important during the active growing season. The “tray method” of watering is recommended, where pots sit in a shallow tray of distilled, reverse osmosis (RO), or clean rainwater. Avoid using tap water, as dissolved minerals and salts can accumulate in the soil and harm the plant. While the plant needs consistent moisture, the soil should not be waterlogged, and very deep pots are suggested to keep the water table below the tuber depth.
Growing Medium
The ideal growing medium for Drosera erythrorhiza must be nutrient-poor, well-draining, and acidic, replicating its native sandy or lateritic soils. A common mix is a blend of peat moss and silica sand, often in a 1:1 or 2:1 sand-to-peat ratio. Conventional potting soil is unsuitable due to its nutrient content. Avoid sharp-edged sand, as it can compact and impede tuber development; silica sand, particularly pool filter sand, is preferred for its rounded edges.
Temperature and Humidity
During its active growth, Drosera erythrorhiza prefers cooler temperatures, typically 40°F to 75°F (4°C to 24°C). High temperatures can induce premature dormancy, which may be detrimental if the tuber has not fully developed. While humidity is not as critical for this species as for some tropical sundews, moderate levels are beneficial.
Managing Dormancy
Dormancy is a necessary phase in the life cycle of Drosera erythrorhiza, mimicking the hot, dry summer conditions of its Western Australian habitat. As the growing season concludes, typically with rising temperatures and reduced moisture, the plant’s above-ground foliage will begin to yellow and die back.
To initiate dormancy, gradually reduce watering as the leaves decline, allowing the soil to dry out almost completely. Once the foliage has died back, the tuber remains dormant underground. The pot containing the tuber should be kept dry and stored in a cool, dark place, mimicking its underground environment. Ideal storage involves keeping the tuber in its slightly damp growing medium or in a small bag with slightly moist peat or sand. Dormancy typically lasts several months, often from late spring through early autumn. To re-initiate growth, usually in early autumn, gradually reintroduce water to the pot. Cooler temperatures and increased moisture will signal the tuber to sprout and begin a new growing cycle.
Propagation
Propagating Drosera erythrorhiza can be achieved through seed or by dividing its tubers. Growing from seed requires specific conditions for germination. Seeds generally need a period of cold stratification, mimicking the cool, moist winter conditions they would experience in their natural environment before sprouting. Once stratified, seeds can be sown on a moist, appropriate growing medium.
Propagation through tuber division is another effective method, particularly for mature plants that produce “daughter” tubers. This process involves carefully excavating the plant during its dormant phase and gently separating any new tubers from the main one. Each separated tuber, ensuring it has a visible “eye” or growth point, can then be planted individually.
Troubleshooting Common Problems
Growers of Drosera erythrorhiza may encounter several common issues, often related to incorrect environmental conditions. A lack of dew on the plant’s leaves is a frequent problem, typically indicating insufficient light. Increasing the intensity or duration of light exposure, whether natural or artificial, often resolves this. Stunted growth can also be a symptom of inadequate light, or it may point to issues with the growing medium, such as a lack of proper drainage or excessive nutrients.
Failure to emerge from dormancy is another concern. This can occur if the tuber was stored improperly, if the dormancy period was too short or too warm, or if water reintroduction was not timed correctly with cooler temperatures. Ensuring a complete and appropriate dry, cool dormancy, followed by careful rehydration, helps prevent this issue.