Bog Arum (Calla palustris) is a distinctive wetland plant, appreciated for its unique appearance, also known as Water Arum or Wild Calla. This herbaceous perennial is the sole species within the Calla genus. It thrives in water-saturated environments, making it suitable for bog gardens and water features. Its common names reflect its preference for marshy habitats.
Understanding Bog Arum
Bog Arum typically grows 6 to 12 inches tall, featuring smooth, waxy, heart-shaped leaves up to 6 inches long. These leaves emerge from shallow, creeping rhizomes. In late spring, a single flower appears on a stout stem, characterized by a showy, white spathe (a modified leaf) that partially encircles a shorter, yellow-green cylindrical spadix. The spadix is covered with tiny yellow flowers that bloom around June, followed by small, pear-shaped fruits that ripen to bright red in late summer.
Native to temperate and subarctic regions across the Northern Hemisphere, including North America, Europe, and Asia, this plant naturally inhabits bogs, marshes, swamps, and the margins of ponds and slow-moving streams. It is often found in shallow water or muddy, humus-rich soils.
Toxicity and Safety Precautions
All parts of the Bog Arum plant are toxic if ingested, particularly the berries and rhizomes. It contains calcium oxalate crystals, which are responsible for its poisonous properties. These needle-like crystals can cause immediate and severe irritation upon contact with mucous membranes.
Symptoms of poisoning in humans and pets include intense burning and swelling of the lips, mouth, tongue, and throat, leading to difficulty speaking or swallowing. Gastrointestinal upset, such as nausea and vomiting, may also occur. When handling Bog Arum, wearing gloves is advisable to prevent skin irritation. Keep the plant away from children and pets who might ingest its attractive berries.
Growing Bog Arum
Cultivating Bog Arum requires mimicking its natural wetland habitat. It thrives in consistently moist to wet conditions, ideally in boggy soil or with its roots submerged in shallow, still water up to 2 inches deep. It prefers acidic to neutral, humus-rich soil that retains moisture well.
Bog Arum performs best in partial shade, though it can tolerate full shade, where stems may become weaker. In northern climates, it can adapt to full sun, provided the soil remains adequately moist. This perennial is cold-hardy, typically growing in USDA Zones 2 through 6. When planting, place it at the margins of a pond or in a constructed bog garden.
Propagation and Ongoing Care
Bog Arum can be propagated through the division of its creeping rhizomes, best undertaken in spring or early summer. While possible, growing from seeds requires specific conditions, including cold stratification, to encourage germination.
Once established, Bog Arum requires minimal care. Fertilization is generally unnecessary, especially in a nutrient-rich bog environment. Removing dead or yellowing foliage helps maintain the plant’s appearance and health. Bog Arum is resistant to serious insect pests or diseases.