Chrysalidocarpus onilahensis (Dypsis onilahensis)

1. Introduction

Chrysalidocarpus onilahensis, now scientifically recognized as Dypsis onilahensis, is a palm species native to Madagascar, specifically found in the northern regions of the island. This palm belongs to the tropical rainforest understory, where it has evolved to thrive in partially shaded conditions with high humidity. Madagascar, as an island with remarkable biodiversity and high endemism rates, is home to numerous unique palm species, with Dypsis onilahensis being one of its botanical treasures.

Scientific Classification:

• Kingdom: Plantae
• Division: Angiosperms
• Class: Monocots
• Order: Arecales
• Family: Arecaceae
• Genus: Dypsis (formerly Chrysalidocarpus)
• Species: D. onilahensis

Synonyms: Chrysalidocarpus onilahensis, Neodypsis onilahensis

Common Names: Onilah Palm, Madagascar Feather Palm

The expansion of this palm in cultivation worldwide has been limited, making it relatively rare in collections outside specialized botanical gardens and the collections of dedicated palm enthusiasts. Its limited availability can be attributed to its specific growing requirements and the challenges associated with seed availability from its native habitat, which has faced significant deforestation pressures. In recent decades, conservation efforts and specialized nurseries have helped increase its presence in tropical and subtropical regions, particularly in parts of Florida, Hawaii, Australia, and Southeast Asia where climatic conditions are suitable.

2. Biology and Physiology

Morphology: The Dypsis onilahensis is a medium-sized palm, typically reaching heights of 15-25 feet (4.5-7.5 meters) at maturity. The stem (trunk) is slender, measuring approximately 3-4 inches (7.5-10 cm) in diameter, and displays distinctive leaf scars in a ringed pattern. It may form clusters with multiple stems emerging from the base over time.

The leaves are pinnate (feather-like), arching gracefully and reaching lengths of 5-8 feet (1.5-2.4 meters). Each leaf consists of numerous narrow leaflets arranged along the rachis, creating the characteristic feathery appearance. The leaflets are dark green on the upper surface with a slightly lighter undersurface, and they display a distinct midrib.

The inflorescence (flower system) emerges from among the leaves, bearing small, cream-colored flowers arranged on branching rachillae. The male and female flowers are produced on the same inflorescence (monoecious), with fertilization typically facilitated by insects.

Life Cycle: Like most palms, Dypsis onilahensis follows a monopodial growth pattern, with a single growing point. The life cycle begins with seed germination, followed by a juvenile phase characterized by the development of increasingly complex leaves. The juvenile phase may last several years before the palm reaches reproductive maturity and begins flowering. Once mature, the palm will flower seasonally, with fruiting occurring several months after successful pollination. The fruits develop into small, oval drupes that turn from green to yellow-orange when ripe.

Specific Adaptations: This species has evolved specific adaptations to its native understory habitat, including:

• Tolerance to partial shade, allowing it to thrive beneath the forest canopy
• Efficient photosynthesis under lower light conditions
• Adaptations to consistent moisture and humidity levels
• Limited tolerance to temperature extremes, particularly cold

3. Reproduction and Propagation

Seed Reproduction: Dypsis onilahensis is primarily propagated through seeds, as vegetative propagation methods are typically unsuccessful with this species.

Seed Morphology: The seeds are oval to elliptical, measuring approximately 0.4-0.6 inches (10-15 mm) in length. They have a thin, fibrous outer covering (mesocarp) and a hard endocarp surrounding the endosperm and embryo. Fresh seeds have a cream to light brown color, darkening with age.

Seed Collection and Viability Testing: Seeds should be collected when fruits turn yellow-orange, indicating ripeness. After collection, the fleshy mesocarp should be removed to prevent fermentation and potential damage to the embryo. Viability can be tested through flotation methods (viable seeds sink in water) or by cutting a sample seed to examine the endosperm, which should be firm and white in viable specimens.

Pre-germination Treatments:

• Scarification is generally not required for this species
• A warm water soak (24-48 hours, changing water daily) can help soften the seed coat and initiate imbibition
• A fungicide treatment may be beneficial to prevent fungal infection during germination

Germination Techniques: For optimal germination:

1. Use a well-draining medium composed of equal parts perlite and peat moss or coir
2. Plant seeds horizontally, half-buried in the medium
3. Maintain temperature between 80-85°F (27-29°C)
4. Ensure consistent high humidity (80-90%) using clear plastic covers or propagation chambers
5. Provide bottom heat if possible to maintain warm soil temperatures

Germination Difficulty: Moderate to difficult

Germination Time: Variable, typically 2-4 months, though some seeds may take up to 6 months

Seedling Care: Once germinated, seedlings should be maintained in high humidity with filtered light. The first leaf (eophyll) is typically undivided, with subsequent leaves gradually developing the characteristic pinnate form. Seedlings should be transplanted to individual containers when they have developed 2-3 leaves, using a well-draining palm mix. Protection from direct sunlight is essential for the first year of growth.

Advanced Germination Techniques: Hormonal treatments, such as applications of gibberellic acid (GA3) at concentrations of 200-500 ppm, may enhance germination rates and reduce germination time. However, these treatments require careful application and monitoring to prevent embryo damage.

4. Cultivation Requirements

Light Requirements: Dypsis onilahensis performs best in filtered light or partial shade, mimicking its natural understory habitat. Young plants require more protection from direct sunlight than mature specimens.

• Seasonal adjustments: Increase shade during summer months in subtropical regions
• Artificial lighting: When grown indoors, bright indirect light or grow lights providing 2000-3000 lux are beneficial

Temperature and Humidity Management:

• Optimal temperature range: 70-85°F (21-29°C)
• Minimum temperature tolerance: Brief exposure to 45°F (7°C) may be tolerated, but prolonged temperatures below 50°F (10°C) can cause damage
• Hardiness zone: USDA zones 10b-11, with marginal success in protected locations in zone 10a
• Humidity requirements: High humidity (60-80%) is strongly preferred, particularly for younger plants

Soil and Nutrition: The ideal soil composition includes:

• 40% organic matter (peat, compost, or coir)
• 30% coarse sand or perlite
• 20% pine bark or orchid bark
• 10% charcoal
• pH range: 5.5-6.5 (slightly acidic)

Nutrient requirements vary through growth stages:

• Seedlings benefit from quarter-strength balanced fertilizer (e.g., 10-10-10) applied monthly
• Juvenile plants require balanced fertilization with micronutrients, applied every 2-3 months
• Mature specimens benefit from a palm-specific fertilizer (e.g., 8-2-12 with micronutrients) applied 3-4 times annually

Common micronutrient deficiencies include:

• Magnesium deficiency (yellowing of older fronds)
• Manganese deficiency (necrotic spotting)
• Potassium deficiency (translucent spotting and frond tip necrosis)

These can be corrected through applications of appropriate supplements and maintaining proper soil pH to ensure nutrient availability.

Water Management:

• Irrigation frequency: Maintain consistent moisture without waterlogging; typically water when the top inch of soil becomes dry
• Drought tolerance: Low; this species shows rapid stress symptoms when subjected to drought conditions
• Water quality: Sensitive to high mineral content, particularly chlorine and fluoride; rainwater or filtered water is preferable
• Drainage: Excellent drainage is critical to prevent root rot; elevated containers or raised beds are beneficial in landscape settings

5. Diseases and Pests

Common Problems: Dypsis onilahensis may face several cultivation challenges, including:

Disease Identification and Management:

• Fungal diseases:

  • Leaf spot (Helminthosporium, Pestalotiopsis): Presents as brown spots with yellow halos; treat with copper-based fungicides and improve air circulation
  • Root rot (Phytophthora, Pythium): Causes wilting and yellowing despite adequate moisture; improve drainage and treat with appropriate fungicides
  • Bud rot (Phytophthora palmivora): Fatal if it reaches the growing point; preventative fungicide applications during wet periods are essential

• Bacterial infections:

  • Bacterial bud rot: Similar symptoms to fungal bud rot but requires bactericide treatments
  • Leaf streak: Creates water-soaked streaks along leaflets; remove affected tissues and apply copper-based bactericides

Pest Identification and Management:

• Spider mites: Particularly problematic in dry conditions; increase humidity and use miticides or horticultural oils
• Scale insects: Form colonies on leaf undersides and stems; treat with horticultural oil or systemic insecticides
• Mealybugs: White, cottony masses in leaf axils; remove with alcohol-soaked cotton swabs or treat with insecticidal soap
• Palm aphids: Cluster on new growth; control with insecticidal soap or neem oil

Environmental and Chemical Protection Methods:

• Cultural practices:

  • Maintain appropriate spacing for air circulation
  • Avoid overhead irrigation, particularly in cooler weather
  • Remove and destroy affected plant parts promptly
  • Quarantine new plants before introducing them to collections

• Biological controls:

  • Beneficial insects such as ladybugs and lacewings for aphid control
  • Predatory mites for spider mite management
  • Bacillus thuringiensis for caterpillar infestations

• Chemical controls:

  • Use as a last resort and rotate chemical classes to prevent resistance
  • Apply according to label instructions, particularly regarding timing and concentration
  • Consider environmental impact and potential harm to beneficial organisms

6. Indoor Palm Growing

Specific Care in Housing Conditions: Dypsis onilahensis can be grown indoors with appropriate care:

• Placement: East or north-facing windows provide ideal light; south or west windows require sheer curtains to filter direct sunlight
• Humidity: Use humidifiers, pebble trays, or grouping with other plants to maintain elevated humidity
• Air circulation: Provide gentle air movement without cold drafts
• Cleaning: Regular leaf cleaning with a damp cloth prevents dust accumulation and discourages pests

Replanting and Wintering:

• Repotting should be done when roots become visible at drainage holes, typically every 2-3 years
• Choose containers only 2-3 inches larger than the previous pot to prevent overwatering issues
• The best time for repotting is during the active growing season (spring to early summer)
• During winter in temperate regions:
  • Reduce watering frequency but maintain consistent moisture
  • Discontinue fertilization until spring
  • Move away from cold windows and drafts
  • Supplement with grow lights if natural light is insufficient during shorter days
  • Maintain temperatures above 60°F (15°C)

7. Landscape and Outdoor Cultivation

When used in landscape settings, Dypsis onilahensis serves as an elegant specimen plant or understory component in tropical garden designs. Its slender form and graceful foliage make it suitable for smaller spaces where larger palms would be overwhelming.

Establishment and Maintenance in Landscapes:

• Planting techniques for success:

  1. Select locations with filtered light, protection from strong winds, and well-draining soil
  2. Dig planting holes twice the width of the root ball but no deeper than the container depth
  3. Incorporate organic matter and sand to improve drainage if native soil is heavy
  4. Position the palm at the same depth as it was growing in its container
  5. Create a watering basin around the palm and apply 2-3 inches of organic mulch, keeping it away from the trunk
  6. Water thoroughly after planting and maintain consistent moisture during the establishment period (typically 3-6 months)

• Long-term maintenance schedules:

  1. Year 1: Water 2-3 times weekly during dry periods; fertilize lightly with palm-specific fertilizer every 3 months; monitor closely for stress indicators
  2. Year 2: Reduce watering to once weekly unless drought conditions occur; continue quarterly fertilization; begin preventative pest monitoring
  3. Years 3+: Establish regular maintenance routine including:
     • Trimming only completely brown fronds, leaving partially green fronds to support photosynthesis
     • Applying fertilizer 3-4 times annually, focusing on the growing season
     • Monitoring for nutritional deficiencies and addressing promptly
     • Inspecting regularly for pest or disease issues

8. Cold Climate Cultivation Strategies

Cold Hardiness: As a tropical species, Dypsis onilahensis has limited cold tolerance. Leaf damage typically occurs at temperatures below 45°F (7°C), with more severe damage or death possible with prolonged exposure to temperatures below 40°F (4°C).

Hardiness Zone: This palm is best suited to USDA Zones 10b-11, though it may survive in protected microclimates in Zone 10a with appropriate winter protection.

Winter Protection Systems: In marginal climates, several protection methods can be employed:

1. Anti-transpirant sprays applied to foliage before cold weather to reduce moisture loss
2. Ground mulching with 4-6 inches of organic material to protect root zones
3. Trunk wrapping with insulating materials such as palm frost cloth or burlap
4. Canopy protection using frost cloth or specialized palm tents
5. Temporary heat sources such as outdoor-rated string lights or heat cables for extreme cold events

Winter Protection Materials:

• Frost cloth (preferred over plastic as it allows air exchange)
• Burlap wrapping
• Christmas lights (incandescent, not LED) for heat generation
• Mulch materials (straw, pine bark, leaves)
• Commercial palm winter protection systems

For collectors in colder regions, containerized specimens should be moved indoors or to protected areas such as greenhouses or sunrooms during winter months.

Final Summary

Chrysalidocarpus onilahensis (Dypsis onilahensis) is a slender, elegant palm native to Madagascar's northern rainforests, characterized by its feathery fronds and clustering growth habit. This moderately difficult species requires filtered light, consistent moisture, high humidity, and protection from cold temperatures to thrive. Propagation occurs primarily through seeds, which germinate over 2-6 months with proper conditions. Indoor cultivation demands attention to humidity and light levels, while outdoor planting is limited to USDA Zones 10b-11. With proper care addressing its specific requirements, this relatively rare palm offers a distinctive tropical aesthetic for both indoor collections and appropriate landscape settings, though it remains challenging for beginning palm enthusiasts.