Sundews (Drosera sp.) are probably the most diverse genus of carnivorous plants in the world which consisting of around two hundred species. Commonly known as sundew because the word, Drosera in Greek means dewy. The “dew” found on the hair of sundew exhibit mini-rainbows whenever they are struck by sunlight. They can be found in Canada, Alaska, Siberia, Europe, Nother America, Brazil, Queensland, southernmost regions of New Zealand, and South America. It occurs on almost all continents except Antarctica. It’s rather exceptional that Sundews adapted to such diverse climates. Most species require wet, acidic, low-nutrient, and low-mineral soil to grow. Whereas, some Drosera are found in bogs that are frozen much of the year. Some have adapted to survive hot and dry climate while growing only in the rainy season.
The sizes of sundews are varied from species to species. It can be as tiny as a penny or as large as a small bush. Apart from the size and color that help to differentiate the species, the imaginative genius design of tentacle-covered leaves plays a pivotal role in Drosera species identification. Namely circular, wedge-shaped, strap-shaped, leaves that are peltate, linear, or filiform as a thin blade of grass. Generally green with deep red color tentacles, the leaves play many roles that include reproduce offsprings, acceptance, and conveyance of stimuli resulting in the bending movements of the tentacles as well as stimulate the production of fluids secretions by the tentacle glands.
The color of sundews flowers is often diversified such as white, pink, red, and purple. Generally reproduced by seeds through self-pollination. Cross-pollination can also be carried out for specific varieties. Besides, sundews can be vegetatively propagated through leaf-cutting by snipping off the leaves at their petioles. Lay the leaves flat with the tentacle facing up on the substrate such as sphagnum moss. Tiny plantlets will appear from the tentacles after several weeks. Budding of new plantlets also can be achieved by floating the leaves in a container containing pure distilled water, replacement of fresh distilled water is required if algae appear. Root cuttings seemed to be an excellent alternative to propagate in which healthy black roots with whitish tips are cut into pieces about two inches. If sundew babies emerged around the mother plant, splitting of the individuals can be performed. Often cultivated on living or preserved sphagnum moss watered with rainwater, reverse osmosis (RO) water, or distilled water that has low mineral content (measure in part per million, PPM). Hobbyists or collectors often feed with fish food that is rich in nutrients on the leaves, with one small piece on each leaf.
The watery and sweet nectar on the leaves makes sundews look sparkling. The flattened leaf surface is covered with fine hairs ending in a series of glands, that carry the drop of clear, colorless, sticky fluid or mucus. The drops of nectar at the tips of tentacles look exactly like morning dew but more functional. They are the visible and odoriferous lure as well as trapping medium, the “lollipop”. However, the lollipop is deadly in which made up of digestive enzymes, mucilage, water, and odiferous substances that aid in the absorption of the prey. The sparkling drops are the living nightmare for their prey, mostly insects. Known as suffocating glue for insects as it makes sure no insects would break free with the grasping tentacles and burning acids and enzymes. The more they struggle, the more the body contact with the sticky drops, and the more it thrashes, the more mired it becomes. If the insect is strong enough, it might win the fight by losing a leg or wing, or it may pull partly free of one leaf of the sundew only to be caught by the tentacles of another.
On the other hand, within moments, some of the tentacles begin to move. The retentive glands along the edge begin to curl inward blocking the panicking insect’s escape, thus, rolling or blanketing the insect, which referred to as a fly sandwich. Making sure the insects are fully bathed and drown in the fluids. Sundews “eat” different sized insects. Tiny insects with their abdomens stick by the glue are usually suffocated as their breathing holes are found on abdomens. But for larger insects, sundews feed on the body parts such as long and thin legs. Occasionally, the larger insects manage to escape by subtracting a few legs but are destined to die later or caught by the spiders that spinning webs around sundews. Interestingly, spiders are also sundew’s prey because they often indirectly attracted by the caught insects on sundew.
Most sundews have these dramatic movements to enfold their leaves around their prey. If the insect was caught at the edge of the leaf, the tentacles would move quickly, carry the prey toward the center of the leaf that has the most glands. Sundews with thin leaves rely strictly on the tentacle movements. Then the secretion of digestive juice containing enzymes occurs afterward. The digested fluid serves as sundews’ nutrients will be absorbed and transported to other parts of the plants. The movement of sundew tentacles and leaves are similar to their relative, Venus flytrap. Cells along one side of a tentacle keep growing and stretching leading to unequal lengths of the cells that caused the bending of the tentacle.
The speed of the tentacle movement depends on factors such as temperature, age of the leaf, species of the plant, how intensive is the struggling movement by the insect, and the size of the insect. It will not react to a pine needle falling on them but will slowly move if they are repeatedly teased with a toothpick. It takes about twenty minutes for tentacles to trap the insect whereas, it may take roughly about eighteen to twenty-four hours for a completely curl leaf around its prey. It will unroll to its former orientation by reversing all the cellular movement in the trapping mechanism when the absorption has been completed. Interestingly, some chemical substances such as creatine can be digested without any visible movement of the tentacles.
Further readings:
Conn, B. J. (1980). A review of Dtorosera in Papuasia. Brunonia, 3(2), 209-216.
Temple, P. (1988). Carnivorous plants.
Pietropaolo, J., Pietropaolo, P. A., & James. Pietropaolo. (1999). Carnivorous plants of the world. Timber Press.
Meyers-Rice, B. (2006). Growing carnivorous plants. Timber Press.
D’amato, P. (2013). The savage garden, revised: Cultivating carnivorous plants. Ten Speed Press.
Baranyai, B., & Joosten, H. (2016). Biology, ecology, use, conservation and cultivation of round-leaved sundew (Drosera rotundifolia L.): a review. Mires and Peat, 18.
