Chrysalidocarpus prestonianus

1. Introduction

Habitat and Distribution

Chrysalidocarpus prestonianus, now classified as Dypsis prestoniana, is a solitary palm native to Madagascar. It is found specifically in the Midongy area of Madagascar, where it grows in moist forest habitats on slight slopes with clay soils derived from laterite at elevations between 50-550 meters. Historically, there was also an old collection from Mahanoro, but recent visits to this area indicate it is now devoid of palm trees, highlighting the species' declining distribution.

Taxonomic Classification

Kingdom: Plantae
Division: Tracheophyta
Class: Liliopsida
Order: Arecales
Family: Arecaceae
Subfamily: Arecoideae
Genus: Dypsis (formerly Chrysalidocarpus)
Species: D. prestoniana

Synonyms

The primary synonym is Chrysalidocarpus prestonianus. The genus Chrysalidocarpus has been largely reclassified, with most species now placed in the genus Dypsis following taxonomic revisions by palm experts.

Common Names

• Preston's Palm
• Midongy Palm

Expansion of This Palm in the World

While endangered in its native habitat, D. prestoniana has been introduced to cultivation in tropical and subtropical regions around the world. It can be found in botanical gardens and specialized palm collections in southern Florida, Hawaii, northern Australia (Queensland), and other frost-free tropical regions. Its striking appearance has made it desirable among palm enthusiasts, though it remains relatively rare in cultivation compared to more common palms.

2. Biology and Physiology

Morphology

Trunk:

• Solitary growth habit (non-clustering)
• Height: 4-12 meters
• Diameter: 24-40 cm
• Basal boss (swollen base): about 15 cm high, 40 cm in diameter
• Internodes: 10-15 cm
• Color: pale grey-brown, distally green and smooth
• Nodal scars: approximately 3.5 cm, pale grey

Leaves:

• Crown consists of 8-10 leaves arranged in a spiral pattern
• Orientation: porrect (extending forward) to spreading, gracefully arched in the distal part
• Sheath: 90% open, green to pale brown or grey, with waxy covering
• Features brown tomentum (fuzzy covering) of peltate scales
• Sheath dimensions: approximately 114 x 28 cm, with distinct rounded shoulders
• Petiole: 0-17 cm, deeply channeled
• Rachis (central leaf stem): approximately 4.4 meters long, channeled in proximal part
• Leaflets: irregularly spaced along the rachis, giving the palm its distinctive appearance

Flower Systems (Inflorescence):

• Position: interfoliar (emerging from among the leaves)
• Structure: erect with spreading or recurved branches
• Branching: to 3 orders (levels of branching)
• Dimensions: approximately 226 x 90 cm
• Peduncle (flower stalk): about 118 cm long
• Color: yellow with brown scales, turning green with red-brown scales

Life Cycle

Like most palms, D. prestoniana follows a monocotyledonous growth pattern. The palm begins from seed, developing a single growing point that will produce the trunk. The life cycle progresses through:

1. Seed germination: The seed germinates remote-tubular style, where the embryo extends away from the seed before emerging.
2. Seedling stage: Initial leaf production with juvenile leaves that are less divided than adult foliage.
3. Establishment phase: Trunk formation and maturation of leaf structure.
4. Reproductive maturity: Flowering begins once the palm reaches sufficient size and maturity.
5. Fruiting: Following pollination, the palm produces numerous orange fruits.
6. Senescence: Eventually, after many decades, the palm will decline and die.

Specific Adaptation to Different Climate Conditions

D. prestoniana has adapted to the specific conditions of its native Madagascar habitat:

• Rainfall adaptation: Evolved in moist forest environments with regular rainfall.
• Soil preferences: Adapted to clay soils derived from laterite.
• Elevation adaptation: Grows at mid-elevations (50-550 meters) where temperatures are moderate.
• Light requirements: Adapted to filtered light conditions typical of forest environments.

In cultivation, it has shown some adaptability to different conditions but performs best when its native habitat conditions are approximated. It requires protection from full sun when young and thrives in humid environments with moderate temperatures.

3. Reproduction and Propagation

Seed Reproduction

Seed Morphology and Diversity

The fruits of D. prestoniana are orange when ripe, containing a single seed with homogeneous endosperm. Seed size and shape are consistent with other members of the genus Dypsis, with oval to round seeds protected by a thin endocarp.

Detailed Seed Collection and Viability Testing

Seeds should be collected when fruits turn orange, indicating ripeness. Viability can be tested through:

• Float test: viable seeds typically sink in water
• Visual inspection: healthy seeds should be firm and filled out
• Cut test: examine a sample seed by cutting it open to check for healthy endosperm

Pre-germination Treatments

Though specific information for D. prestoniana is limited, related Dypsis and Chrysalidocarpus species benefit from:

• Scarification: gently filing or nicking the seed coat to allow water penetration
• Soaking: immersion in warm water (30°C) for 2-4 days before sowing
• Chemical treatments: some palm growers report improved germination with sulfuric acid or acetone treatments

Germination Techniques with Humidity and Temperature Controls

For optimal germination:

• Medium: Use a well-draining mix of peat and perlite or specialized palm seed germination mix
• Container: Deep pots or seedling bags that allow for root development
• Temperature: Maintain consistent warmth between 25-30°C (77-86°F)
• Humidity: Keep consistently moist but not soggy (80-90% humidity)
• Position: Place in bright, indirect light
• Method: Plant seeds 1-2 cm deep in the medium

Germination Difficulty

D. prestoniana has moderate to high germination difficulty, typical of many Madagascar palms. Challenges include:

• Seed viability issues due to recalcitrant nature
• Lengthy germination period
• Specific temperature and humidity requirements
• Sensitivity to drying out during the germination process

Germination Time

Germination is relatively slow, typically taking 2-6 months under optimal conditions. Some seeds may take up to a year to germinate, especially if conditions are not ideal.

Seedling Care and Early Development Stages

Once germinated, seedlings require:

• Consistent moisture but not waterlogging
• High humidity (70%+)
• Bright, filtered light (never direct sun for young seedlings)
• Protection from drafts and temperature fluctuations
• Minimal fertilization until several leaves have developed
• Careful monitoring for pests like spider mites and scale insects

Advanced Germination Techniques

For improved results:

• Bottom heat: Maintaining soil temperature at 28-30°C using heat mats
• Humidity chambers: Creating mini-greenhouses to maintain high humidity
• Sterile techniques: Working in clean conditions to prevent fungal issues

Hormonal Treatments for Germination Enhancement

Growth regulators may improve germination rates:

• Gibberellic acid (GA3) treatments: Soaking seeds in a GA3 solution (500-1000 ppm) for 24 hours prior to sowing
• Cytokinins: Some experiments suggest possible benefits from cytokinin application

4. Cultivation Requirements

Light Requirements

Species-specific Light Tolerance Ranges

D. prestoniana prefers bright, filtered light rather than direct sunlight, especially when young. In its natural habitat, it receives dappled sunlight through the forest canopy. Cultivation recommendations include:

• Young plants: 30-50% shade cloth protection
• Established plants: Can tolerate more light but prefer partial shade
• Indoor cultivation: Bright indirect light, avoiding direct sun through windows

Seasonal Light Variations and Management

Light management should adjust throughout the year:

• Summer: Increased protection from intense midday sun
• Winter: Maximum available light exposure, especially in temperate regions
• Seasonal transitions: Gradual acclimatization to changing light levels

Artificial Lighting for Indoor Cultivation

For indoor growing, artificial lighting should provide:

• Spectrum: Full-spectrum with emphasis on blue and red wavelengths
• Duration: 12-14 hours daily
• Intensity: 2500-3500 lux (higher than for many houseplants)
• Positioning: Lights should be positioned overhead, mimicking natural sunlight

Temperature and Humidity Management

Optimal Temperature Ranges

D. prestoniana thrives in warm conditions:

• Optimal daytime temperature: 24-30°C (75-86°F)
• Optimal nighttime temperature: 18-22°C (65-72°F)
• Minimum tolerance: Around 10°C (50°F) for brief periods
• Growth slows significantly below 18°C (65°F)

Cold Tolerance Thresholds

This species has limited cold tolerance:

• USDA Hardiness Zone: 9b (minimum 25°F/-3.9°C) with protection
• Damage occurs at temperatures below 10°C (50°F) for extended periods
• Frost will cause severe damage or death
• Young plants are more susceptible to cold damage than mature specimens

Humidity Requirements and Modification Techniques

As a tropical palm, D. prestoniana requires high humidity:

• Optimal humidity: 60-80%
• Minimum tolerance: 40% (though health declines in consistently dry air)

Humidity modification techniques include:

• Misting: Regular fine misting of the foliage
• Grouping plants: Creating a microclimate of higher humidity
• Humidity trays: Placing containers on trays filled with pebbles and water
• Humidifiers: Using room humidifiers in dry indoor environments

Soil and Nutrition

Ideal Soil Composition and pH Values

D. prestoniana performs best in:

• Soil type: Rich, well-draining but moisture-retentive mix
• Composition: 30-40% high-quality potting soil, 30% coarse materials (perlite, lava rock), 30% organic matter (bark, coir)
• pH range: Slightly acidic to neutral (6.0-7.0)
• Structure: Loose enough to allow root growth but stable enough to anchor the palm

Nutrient Requirements Through Growth Stages

Nutritional needs vary by growth stage:

• Seedlings: Minimal fertilization, diluted to 1/4 strength if used
• Juvenile plants: Balanced fertilizer with micronutrients (NPK 3-1-3 or similar ratio)
• Mature plants: Increased potassium for stronger growth and disease resistance

Organic vs. Synthetic Fertilization Approaches

Both approaches can be effective:

Organic options:

• Compost: Slow-release nutrients and improved soil structure
• Fish emulsion: Natural nitrogen source
• Seaweed extracts: Micronutrients and growth stimulants
• Palm-specific organic blends: Formulated for palm requirements

Synthetic options:

• Controlled-release fertilizers: Consistent nutrient delivery over 3-6 months
• Liquid fertilizers: Quick nutrient availability and precise control
• Palm-specific formulations: Balanced for palm requirements with added magnesium and micronutrients

Micronutrient Deficiencies and Corrections

Common deficiencies to monitor:

• Magnesium: Yellowing on older fronds while veins remain green
• Manganese: New leaves emerge with yellow/brown spots and stunted growth
• Iron: New leaves emerge pale yellow to white while veins remain green
• Boron: Deformed new growth, "hook leaf" symptoms

Corrections include:

• Magnesium sulfate (Epsom salt) applications for magnesium deficiency
• Manganese sulfate for manganese deficiency
• Iron chelate applications for iron deficiency
• Borax or boric acid (highly diluted) for boron deficiency

Water Management

Irrigation Frequency and Methodology

D. prestoniana requires consistent moisture without waterlogging:

• Frequency: Allow the top 2-3 cm of soil to dry between waterings
• Method: Deep, thorough watering that reaches all roots
• Container plants: Water until it flows freely from drainage holes
• In-ground plants: Slow, deep irrigation to encourage deep rooting

Seasonal adjustments:

• Summer: Increased frequency in hot weather
• Winter: Reduced watering during cooler periods or slow growth
• Monitoring: Adjust based on environmental conditions rather than strict schedule

Drought Tolerance Assessment

D. prestoniana has low to moderate drought tolerance:

• Can withstand short periods (1-2 weeks) of reduced water
• Shows stress through leaf tip browning and reduced growth
• Recovery occurs with resumed watering if drought is not prolonged
• Not suitable for xeriscape or low-water landscaping

Water Quality Considerations

Water quality significantly impacts health:

• Chlorine/chloramine: Allow tap water to stand 24 hours before use or use filtration
• Salinity: Low tolerance for salt in irrigation water
• pH: Prefers slightly acidic to neutral water (pH 6.0-7.0)
• Temperature: Room temperature water is ideal; avoid cold water shock

Drainage Requirements

Proper drainage is essential:

• Container drainage: Multiple drainage holes in pots
• Soil permeability: Should allow water to flow through within minutes
• Root aeration: Avoid compacted soils that restrict oxygen
• Raised planting: In heavy soils, plant in slightly raised beds or mounds

5. Diseases and Pests

Common Problems in Growing

D. prestoniana can experience several cultivation challenges:

• Slow establishment after transplanting
• Sensitivity to environmental stresses (temperature, humidity, light)
• Vulnerability to overwatering and poor drainage
• Difficulty recovering from severe damage or defoliation

Identification of Diseases and Pests

Diseases:

1. Leaf Spot Fungi

   • Symptoms: Circular to elongated brown spots, possibly oily in appearance
   • Cause: Various fungal pathogens
   • Impact: Primarily aesthetic unless severe

2. Root Rot

   • Symptoms: Yellowing fronds, wilting, blackened roots
   • Cause: Phytophthora and other fungal pathogens
   • Impact: Can be fatal if left untreated

3. Lethal Yellowing

   • Symptoms: Progressive yellowing beginning with oldest fronds, flower/fruit drop
   • Cause: Phytoplasma bacteria spread by planthopper insects
   • Impact: Usually fatal; infected palms typically die within months

4. Bud Rot

   • Symptoms: Central new growth dies, can't be pulled out easily
   • Cause: Various fungi, often following mechanical injury or stress
   • Impact: Often fatal as it affects the palm's single growing point

Pests:

1. Spider Mites

   • Identification: Tiny, often red or brown, webbing on undersides of leaves
   • Damage: Stippling, yellowing, bronzing of leaf surfaces
   • Severity: Can cause significant stress if populations are high

2. Scale Insects

   • Identification: Small, round, immobile bumps on stems and leaves
   • Damage: Yellowing, stunted growth, honeydew secretions
   • Severity: Can weaken plants significantly over time

3. Mealybugs

   • Identification: White, cottony masses on leaf bases and growing points
   • Damage: Weakened growth, honeydew production, sooty mold
   • Severity: Moderate to serious if untreated

4. Palm Aphids

   • Identification: Small, soft-bodied insects clustered on new growth
   • Damage: Distorted new growth, honeydew secretions
   • Severity: Usually minor unless populations are very high

Environmental and Chemical Protection Methods

Cultural Controls:

• Maintain optimal growing conditions to reduce plant stress
• Ensure proper spacing for air circulation
• Avoid overhead irrigation that wets foliage
• Remove and dispose of infected plant material
• Use clean tools when pruning to prevent disease spread

Biological Controls:

• Beneficial insects like ladybugs and lacewings for aphid and mealybug control
• Predatory mites for spider mite management
• Beneficial nematodes for soil-dwelling pests
• Microbial products containing Bacillus thuringiensis for caterpillar pests

Chemical Controls:

For diseases:

• Copper-based fungicides for leaf spots and some bacterial infections
• Systemic fungicides containing phosphorus acid for Phytophthora
• Preventative fungicidal applications during wet periods

For pests:

• Insecticidal soaps for soft-bodied insects like aphids
• Horticultural oils for scale insects and mealybugs
• Systemic insecticides (using with caution and following label directions)
• Growth regulators that disrupt insect development

Integrated Pest Management (IPM):

• Regular monitoring for early detection of problems
• Identification of specific pathogens or pests before treatment
• Use of least-toxic methods first
• Combining cultural, biological, and chemical approaches as needed
• Preventative measures rather than reactive treatments

6. Indoor Palm Growing

Specific Care in Housing Conditions

D. prestoniana can be grown indoors, though it is challenging due to its eventual size. Considerations include:

Positioning:

• Place near east or west-facing windows for bright, indirect light
• Avoid heating/cooling vents that create drafts
• Rotate periodically to ensure even growth
• Provide adequate space for frond spread (minimum 2-meter diameter)

Environmental Adjustments:

• Supplement humidity through humidifiers or misting
• Provide good air circulation without drafts
• Maintain consistently warm temperatures (21-27°C/70-80°F)
• Consider grow lights in low-light situations

Container Selection:

• Use substantial containers with excellent drainage
• Select containers 1/3 larger than the root ball
• Choose materials that don't dry out too quickly (glazed ceramic, plastic)
• Consider decorative outer pots with inner grow pots for ease of maintenance

Grooming and Cleaning:

• Dust leaves regularly with a damp cloth
• Remove only completely brown or dead fronds
• Clean the base of the plant to prevent pest harborage
• Monitor consistently for early signs of problems

Replanting and Wintering

Repotting:

• Frequency: Every 2-3 years for young plants, less often for mature specimens
• Timing: Spring to early summer during active growth
• Method: Minimize root disturbance, maintain same planting depth
• Medium: Fresh, well-draining palm mix
• Aftercare: Reduce fertilization for 4-6 weeks, maintain consistent moisture

Wintering Considerations:

• Reduce water slightly but never allow to dry completely
• Maintain temperatures above 15°C (60°F)
• Increase humidity with humidifiers or grouping plants
• Move away from cold windows or drafty areas
• Provide maximum available light during shorter winter days
• Hold off on fertilizing until days begin to lengthen in late winter
• Monitor carefully for pests, which often increase during winter indoor conditions

7. Landscape and Outdoor Cultivation

D. prestoniana can be stunning in landscape settings where climate permits, though its rarity usually limits it to specialty collections and botanical gardens.

Cold Climate Cultivation Strategies

Cold Hardiness

D. prestoniana has limited cold tolerance, generally requiring USDA Zone 9b or warmer for outdoor cultivation. This means minimum temperatures should rarely drop below 25°F/-3.9°C. Even within this zone, it performs best in protected microclimate areas.

Winter Protection

In marginal climates, protection methods include:

• Temporary greenhouse structures
• Anti-transpirant sprays to reduce moisture loss
• Trunk wrapping with insulating materials
• Mulching heavily around the root zone
• Heat cables or lights for extreme events
• Covering the entire palm during freezes

Hardiness Zone Considerations

Best suited to:

• USDA Zones 10a-11: Excellent performance
• USDA Zone 9b: Possible with protection
• Below Zone 9b: Not recommended for permanent outdoor planting

Winter Protection Systems and Materials

Effective protection includes:

• Frost cloth or agricultural fleece
• Insulating materials like bubble wrap or closed-cell foam
• Christmas lights (incandescent) for slight heat generation
• Temporary structures made from PVC pipe and plastic sheeting
• Commercial palm coats designed specifically for cold protection
• Mulch materials like straw, pine needles, or leaves

Establishment and Maintenance in Landscapes

Planting Techniques for Success

• Site selection: Protected locations with filtered light
• Soil preparation: Amend heavy soils with organic matter and drainage materials
• Planting depth: Set at same level as container growth, never deeper
• Mulching: Apply 5-10 cm of organic mulch, keeping away from trunk
• Initial watering: Create a watering basin and irrigate deeply

Long-term Maintenance Schedules

• Watering: Regular deep watering during first 1-2 years, then as needed
• Fertilization: 3-4 times yearly with palm-specific fertilizer
• Pruning: Remove only completely dead fronds; never "hurricane cut"
• Mulch renewal: Refresh organic mulch annually without building up against trunk
• Pest monitoring: Regular inspections, especially during stress periods
• Cold protection: Temporary measures during unexpected freezes
• Cleaning: Remove fallen fronds and fruit to reduce pest harborage

8. Final Short Summary

Chrysalidocarpus prestonianus (now Dypsis prestoniana) is a rare, elegant solitary palm native to Madagascar's moist forests. Discovered in 1992 and named after Paul Preston who sponsored palm research, it faces vulnerability in the wild with fewer than 200 specimens remaining in its native habitat. This medium-sized palm features a slender trunk (24-40 cm diameter) and graceful crown of 8-10 arching fronds with irregularly-spaced leaflets.

In cultivation, D. prestoniana requires warm temperatures (above 10°C/50°F), high humidity (60-80%), bright filtered light, and consistently moist but well-draining soil. Propagation is primarily by seed, which can take 2-6 months to germinate under optimal conditions. The palm faces challenges from pests like spider mites, mealybugs, and scale insects, as well as fungal diseases including leaf spots and root rot.

Best suited to USDA Zones 10-11, it can be grown as a container specimen in cooler regions if protected from cold. Despite cultivation challenges, D. prestoniana's striking appearance and rarity make it a prized addition to specialized palm collections and suitable for indoor growing where sufficient space allows. Conservation efforts remain important as its native population continues to decline due to habitat loss in Madagascar.