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

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 ranges from 4-12 meters with a diameter of 24-40 cm. A distinctive feature is the basal boss (swollen base), about 15 cm high and 40 cm in diameter. Internodes are 10-15 cm long, pale grey-brown in color, distally green and smooth. Nodal scars are approximately 3.5 cm, pale grey.

Leaves

The crown consists of 8-10 leaves arranged in a spiral pattern. Orientation is porrect (extending forward) to spreading, gracefully arched in the distal part. The sheath is 90% open, green to pale brown or grey, with a waxy covering and distinct rounded shoulders. It features brown tomentum (fuzzy covering) of peltate scales. The rachis (central leaf stem) is approximately 4.4 meters long. Leaflets are irregularly spaced along the rachis, giving the palm its distinctive appearance.

Flower Systems (Inflorescence)

Position is interfoliar (emerging from among the leaves). The structure is erect with spreading or recurved branches, branching to 3 orders. Dimensions are approximately 226 x 90 cm. The peduncle (flower stalk) is about 118 cm long, 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.

• Seed germination: Remote-tubular style.
• Seedling stage: Initial leaf production with juvenile leaves.
• Establishment phase: Trunk formation and maturation of leaf structure.
• Reproductive maturity: Flowering begins once sufficient size is reached.
• Fruiting: Produces numerous orange fruits.
• Senescence: Declines and dies after many decades.

Specific Adaptation to Different Climate Conditions

D. prestoniana has adapted to the specific conditions of its native Madagascar habitat, specifically moist forest environments at mid-elevations (50-550 meters). In cultivation, 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. Viability can be tested through the float test (viable seeds typically sink) or a cut test (checking for firm endosperm).

Pre-germination Treatments

• Scarification: Gently filing the seed coat to allow water penetration.
• Soaking: Immersion in warm water (30°C) for 2-4 days before sowing.
• Chemical treatments: Sulfuric acid or acetone treatments may improve germination (use caution).

Germination Techniques

For optimal germination, use a well-draining mix of peat and perlite. Maintain consistent warmth between 25-30°C (77-86°F) and high humidity (80-90%). Plant seeds 1-2 cm deep.

Germination Time

Germination is relatively slow, typically taking 2-6 months under optimal conditions. Some seeds may take up to a year.

Seedling Care

Seedlings require consistent moisture, high humidity (70%+), bright filtered light (no direct sun), and protection from drafts. Advanced techniques like bottom heat (28-30°C) and Gibberellic acid (GA3) soaks can improve results.

4. Cultivation Requirements

Light Requirements

D. prestoniana prefers bright, filtered light. Young plants need 30-50% shade cloth protection. Established plants can tolerate more light but prefer partial shade. Indoors, provide bright indirect light (2500-3500 lux) for 12-14 hours daily.

Temperature and Humidity

Soil and Nutrition

Fertilize with a balanced fertilizer (NPK 3-1-3 ratio) with micronutrients. Potassium is crucial for mature plants. Watch for Magnesium (yellowing older fronds) and Manganese (spots on new leaves) deficiencies.

Water Management

Water deeply and thoroughly, allowing the top 2-3 cm of soil to dry between waterings. Use water with low salinity and neutral pH. Good drainage is essential to prevent root rot.

5. Diseases and Pests

Common Problems

D. prestoniana is vulnerable to slow establishment and environmental stress. Identifying issues early is key.

Diseases

• Leaf Spot Fungi: Circular brown spots. Treat with copper-based fungicides.
• Root Rot: Yellowing fronds, wilting. Caused by Phytophthora. Requires systemic fungicides.
• Lethal Yellowing: Progressive yellowing, fatal. Caused by Phytoplasma bacteria.
• Bud Rot: Central new growth dies. Often fatal.

Pests

• Spider Mites: Tiny red/brown pests causing stippling. High humidity helps prevent them.
• Scale Insects: Immobile bumps on stems. Treat with horticultural oil.
• Mealybugs: White cottony masses. Weakens growth.

6. Indoor Palm Growing

Growing D. prestoniana indoors is challenging due to its size. Place near east/west windows for bright indirect light. Maintain temperatures between 21-27°C and high humidity. Use large containers with excellent drainage and repot every 2-3 years.

Wintering

Reduce water slightly in winter but do not let dry out completely. Keep temperatures above 15°C and increase humidity to combat dry indoor air.

7. Landscape and Outdoor Cultivation

Cold Climate Strategies

This palm is best suited for USDA Zones 10a-11. In Zone 9b, it requires protection.

Establishment

Plant in protected locations with filtered light. Amend heavy soils with organic matter. Water deeply during the first 1-2 years. Prune only dead fronds.