Amorphophallus impressus is a unique plant with a distinctive inflorescence and growth cycle, making it a compelling addition to a plant collection. Successful cultivation requires understanding its specific needs, particularly its tropical origins and dormancy period.
Discovering Amorphophallus impressus
Amorphophallus impressus is a species within the Amorphophallus genus, belonging to the Araceae family. This plant originates from Malawi and Tanzania in Eastern Africa, typically growing in secondary forests or disturbed areas within primary forests in lowland regions. It forms stoloniferous patches, producing stalks up to 30 inches (76 cm) tall. Its solitary leaf can be substantial, with a petiole around 100 cm (39 inches) long that is green with purple spots, and a leaf blade spreading to about 100 cm (39 inches) in diameter.
Cultivating Amorphophallus impressus
Successful cultivation of Amorphophallus impressus involves providing specific environmental conditions that mimic its natural habitat. This includes careful attention to light, soil, watering, temperature, humidity, and nutrition during both active growth and dormancy.
Light Requirements
Amorphophallus impressus prefers conditions from part sun to shade. During its active growing phase, it thrives in bright, indirect light, mimicking the dappled light under a forest canopy. Protecting the plant from intense midday sun helps prevent leaf scorching.
Soil and Potting
Plant the tuber in rich, well-draining soil. An ideal soil mix should contain good organic matter and ensure excellent drainage to prevent waterlogging. A blend of garden soil, sand, and compost can be effective, providing both nutrients and aeration. The plant benefits from ample root space, so select a pot that accommodates its growing tuber.
Watering Regimen
During active growth, keep the soil consistently hydrated, but avoid waterlogging. Watering about once a week generally maintains the right balance. During its dormancy period, which typically occurs in winter, watering needs significantly decrease or cease entirely to prevent tuber rot.
Temperature and Humidity
Amorphophallus impressus thrives in warm and humid environments. It can tolerate temperatures up to 43°C (109°F), but prolonged exposure to extremes can cause stress. Optimal growth temperatures during the active season are typically around 25°C (77°F). Maintaining humidity levels between 65% and 85% is beneficial for its growth.
Fertilization
Supply Amorphophallus impressus with phosphorus, as this nutrient helps the tuber grow larger each year. A liquid fertilizer formulated for tomatoes, diluted to 1/4 strength, can be applied during the growing season. Some growers also recommend fertilizers with a high potassium ratio. Regular fertilization during active growth supports the plant’s robust development.
Dormancy Care
Amorphophallus impressus goes dormant in winter, and proper care during this period is important for its survival. When the leaf begins to yellow and dies back in the fall, watering should be stopped completely. The tuber can then be dug up and stored in a paper bag in a dry location at room temperature until the following spring. If left in the soil in milder climates, the tuber must remain completely dry to prevent rot.
The Unique Flowering Cycle
The flowering cycle of Amorphophallus impressus is a distinctive event. The inflorescence emerges before the leaf, typically in spring. It features a spathe, a modified leaf surrounding the flower structure, and a spadix, the central stalk where the tiny flowers are located. The inflorescence has a “spittoon” shape and can be burgundy and green.
Like many Amorphophallus species, the flowers are pollinated by carrion beetles and flies, producing a scent that resembles decaying flesh. This unique fragrance attracts specific insects as part of its pollination strategy. Male flowers shed pollen after female flowers are receptive, preventing self-pollination in many Amorphophallus species. The spathe may also curl to trap insects, aiding in pollination.
Propagating and Repotting
Amorphophallus impressus can be propagated most reliably through the division of its corms or tubers. It readily produces stoloniferous offshoots. Division should be performed during the plant’s dormant period, typically in autumn or winter, when the corm is sufficiently large and has produced offsets. Each division should possess healthy growth points and a substantial portion of the corm to support new growth.
Repotting is generally recommended annually in spring when the tuber begins its growth cycle. Plant the tuber in its pot for the entire growing season. Transplanting the plant while it is actively growing should be avoided, as disturbing the roots can cause stress or damage.
Addressing Common Challenges
While Amorphophallus impressus is generally robust, growers may encounter a few issues. Fungal or bacterial infections and rot can occur, particularly if tubers are kept in very moist soil at low temperatures during dormancy. If rot is detected, affected parts of the tuber should be generously cut away. Pests are generally not a significant problem for this plant, though nematodes can occasionally be an issue.