What Is the Dead Horse Arum and How Does It Work?
Discover how the Dead Horse Arum uses heat and chemical scents in a complex reproductive strategy that involves temporarily trapping its pollinators.
The dead horse arum, known scientifically as Helicodiceros muscivorus, is a plant native to the Mediterranean islands. It is known for its unusual and highly specialized method of reproduction. The plant produces a large flower with a mottled, flesh-colored spathe covered in dark hairs. This structure, combined with other adaptations, creates an elaborate deception to achieve pollination. Its appearance alone often captures the attention of gardeners and botanists.
The Carrion Flower Deception
The common name “dead horse arum” hints at the plant’s primary method of attraction: a powerful odor. The flower emits a scent that convincingly mimics a rotting corpse, which serves to attract its specific pollinators. This smell is a complex cocktail of chemical compounds, including oligosulphides, which are also found in decaying animal flesh. This olfactory mimicry is so precise it fools insects searching for a place to lay their eggs.
Furthering the illusion, the plant employs visual cues. The large, scoop-like structure called a spathe has a pinkish, mottled coloration and a texture that resembles decomposing tissue. The spathe is also covered in dark, bristle-like hairs, and a tail-like central spike, the spadix, protrudes from the center. This enhances the appearance of a dead animal.
To complete the deception, the dead horse arum generates its own heat through a process called thermogenesis. By raising its temperature, the plant can more effectively vaporize and disperse the foul-smelling compounds, increasing the range of its scent. This warmth also mimics that of a recently deceased animal, making the flower seem like an ideal location for flies to lay their eggs. The plant’s ability to produce heat enhances its mimicry.
Trapping and Pollination Mechanism
Once pollinators, mainly blowflies, are drawn in by the trickery, the plant’s structure ensures they fulfill their purpose. The flies enter a floral chamber at the base of the spadix. The entrance to this chamber is lined with stiff, downward-pointing hairs that allow insects to enter easily but prevent them from leaving. This trapping mechanism facilitates the next stage of pollination.
The plant’s reproductive timing is precisely organized. When a fly enters the trap, only the female flowers at the bottom of the spadix are mature and receptive to pollen. If the visiting fly has recently been to another dead horse arum, it will pollinate these female flowers. The fly remains trapped inside the chamber for about a day.
After this period, the female flowers are no longer receptive, and the male flowers, situated higher up on the spadix, mature and release their pollen. This pollen coats the trapped flies. Subsequently, the bristle-like hairs at the chamber’s entrance wither, allowing the pollen-covered insects to escape. These flies are then free to be lured by another dead horse arum, continuing the cycle.
Native Habitat and Cultivation
The dead horse arum is native to a specific region within the Mediterranean, found on the islands of Corsica, Sardinia, and the Balearic Islands. In these locations, it grows in rocky, coastal environments, often finding a foothold in pockets of gritty, well-drained soil. This habitat preference indicates its adaptation to harsh conditions and soil that does not retain excessive moisture.
For those interested in cultivating this plant, replicating its native conditions is important. It requires soil with excellent drainage to prevent its tuberous root from rotting. The plant enters a dormant period in the summer, during which it should be kept relatively dry. Its potent odor during its late winter or early spring blooming period is a significant consideration for any grower.
Toxicity and Handling
All parts of the dead horse arum are toxic if ingested. The plant’s tissues contain sharp, needle-like calcium oxalate crystals. If any part of the plant is chewed or swallowed, these crystals can cause significant irritation, pain, and swelling of the mouth, tongue, and throat.
Due to this toxicity, caution is advised when handling the plant. It is recommended to wear gloves to prevent the sap from coming into contact with the skin, as it may cause irritation. The plant should also be kept out of reach of children and pets who might be tempted to touch or ingest it.