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1. Introduction

Habitat and Distribution, Native Continent

Phoenicophorium borsigianum is endemic to the granitic inner islands of the Seychelles archipelago in the Indian Ocean, specifically Mahé, Praslin, La Digue, Silhouette, and several smaller islands. This remarkable palm inhabits intermediate and montane forests from near sea level to 800 meters elevation, with highest populations between 200-600 meters. It thrives in areas with annual rainfall of 2,000-4,000mm, high year-round humidity, and protection from direct coastal winds. The species shows preference for steep slopes, valleys, and areas with rich, well-drained soils derived from weathered granite. It often grows alongside other Seychelles endemics including the famous Coco de Mer (Lodoicea maldivica) and forms an important component of the unique palm-rich forests of these ancient islands.

Native range: Seychelles granitic islands, Indian Ocean
Click on markers for details

Taxonomic Classification and Scientific Classification

Synonyms

• Stevensonia borsigiana K.Koch (basionym, 1862)
• Astrocaryum borsigianum (K.Koch) K.Koch
• Nephrosperma vanhoutteanum (H.Wendl.) Balf.f. (misapplied)
• Phoenicophorium sechellarum H.Wendl.

Common Names

• Thief palm (English - most common)
• Latanier feuille (Seychellois Creole)
• Latanier palm (English)
• Seychelles stilt palm (English)
• Palmiste voleur (French - "thief palm")
• 塞舌尔高跷棕 (Chinese)

Expansion in the World

Phoenicophorium borsigianum has achieved moderate distribution in cultivation:

• Common in Seychelles gardens and public spaces
• Singapore Botanic Gardens (well-established specimens)
• Montgomery Botanical Center, Florida
• Fairchild Tropical Botanic Garden
• Hawaii botanical gardens
• Private collections in tropical regions worldwide
• Increasingly available from specialist nurseries
• IUCN Red List status: Vulnerable (due to limited range)

The striking appearance and relative ease of cultivation have made this an increasingly popular ornamental palm.

2. Biology and Physiology

Morphology

Trunk

P. borsigianum develops a solitary, slender trunk reaching 10-15 meters (rarely to 20m) in height with a diameter of 7-15cm. The most distinctive feature is the conspicuous stilt roots that emerge from the trunk base and up to 2 meters above ground, forming a cone-shaped support system. These aerial roots are 5-10cm diameter, smooth, light brown, and can extend 2-3 meters from the trunk base. The trunk itself is gray-brown, closely ringed with leaf scars, and often slightly curved or leaning.

Leaves

The crown consists of 8-15 pinnate leaves forming an elegant, open canopy. Leaves are 2-3 meters long with a distinctive twist that presents different angles. Leaflets number 30-45 per side, irregularly arranged and held in multiple planes, creating the characteristic "messy" appearance that gives the palm its common name "thief palm" (leaves appear disheveled like a thief fleeing). Each leaflet is 40-70cm long and 3-5cm wide, bright green above and slightly paler below with prominent midribs. Young leaves emerge bright red-bronze, creating spectacular color contrast.

Crownshaft

A prominent crownshaft 80-120cm long is formed by the tubular leaf bases. This is bright green to yellow-green, smooth and waxy, swollen at the base. The crownshaft is one of the most attractive features, especially when new leaves emerge.

Flower Systems

P. borsigianum is monoecious with infrafoliar inflorescences emerging below the crownshaft. The branched inflorescence is 60-100cm long, initially enclosed in a boat-shaped bract. Rachillae are numerous (50-150), pendulous, bearing flowers in characteristic triads (two males flanking one female) in the proximal portion and paired or solitary males distally. Male flowers are small (3-4mm), white to cream with 6 stamens. Female flowers are 4-5mm, greenish-white. Flowering occurs throughout the year with peaks during warmer months.

Life Cycle

P. borsigianum has a moderate life cycle typical of medium-sized palms:

• Germination to Seedling (0-3 years): Slow initial establishment
• Juvenile Phase (3-10 years): Stilt root development begins
• Sub-adult Phase (10-20 years): Trunk elongation, first stilt roots
• Adult Phase (20-80 years): Full stilt root development, reproduction
• Senescent Phase (80-120 years): Gradual decline

First flowering typically occurs at 15-20 years or when trunk reaches 3-4 meters.

Specific Adaptations to Climate Conditions

• Stilt Root System: Stability on steep slopes and poor soils
• Multi-plane Leaflets: Maximizes light capture in shaded forest
• Bronze New Leaves: Protection from UV damage
• Flexible Trunk: Survives tropical storms
• Year-round Flowering: Takes advantage of aseasonal climate
• Pioneer Species Traits: Colonizes disturbed areas

3. Reproduction and Propagation

Seed Reproduction

Seed Morphology and Diversity

P. borsigianum produces ellipsoid to ovoid fruits, 12-18mm long and 8-12mm diameter. Immature fruits are green, ripening through yellow to bright red or orange-red. The epicarp is smooth and thin; mesocarp is fleshy and fibrous; endocarp is thin and adheres to the seed. Seeds are ellipsoid, 10-14mm long, with homogeneous endosperm and a basal embryo. The distinctive feature is the sweet, edible mesocarp that attracts birds, particularly the Seychelles bulbul. Fresh seed weight is 0.8-1.5 grams. Genetic diversity is moderate despite the limited range, suggesting good gene flow between populations.

Detailed Seed Collection and Viability Testing

Collection Methods:

• Monitor palms during main fruiting season
• Collect red/orange fruits before bird dispersal
• Net placement helpful for tall palms
• Process within 24-48 hours

Viability Testing:

• Float test: Viable seeds generally sink
• Visual inspection: Plump, firm seeds
• Cut test: White, solid endosperm
• Fresh viability: 85-95%
• One month storage: 70-80%
• Three months: 40-50%
• Six months: 10-20%

Pre-germination Treatments

Fruit Processing:

• Remove fleshy mesocarp completely
• Can ferment 1-2 days
• Clean thoroughly
• Do not allow drying

Scarification:

• Generally not necessary
• Light filing optional
• Natural seed coat thin
• Avoid damage to embryo

Soaking:

• 24-48 hours in warm water
• Change water daily
• Add fungicide to prevent rot
• Seeds may swell slightly

Step-by-step Germination Techniques

1. Medium: 50% peat, 30% perlite, 20% coarse sand
2. Container: Deep pots (20cm+) for taproot
3. Planting: 2-3cm deep
4. Temperature: 26-32°C (79-90°F) optimal
5. Humidity: 75-85%
6. Light: Bright shade immediately
7. Moisture: Evenly moist, never waterlogged

Germination Difficulty

Easy to moderate:

• Fresh seeds germinate readily
• No special treatments required
• Temperature consistency important
• Good drainage essential

Germination Time

• First germination: 30-60 days
• Peak germination: 60-90 days
• Complete process: 120-150 days
• Success rate: 75-90% with fresh seeds

Seedling Care and Early Development

First year:

• Maintain steady conditions
• Begin feeding at 3 months
• 70-80% shade optimal
• Watch for red new leaves

Years 2-3:

• Increase container size
• Regular fertilization program
• Can reduce shade to 60%
• Stilt roots beginning

Years 4-5:

• Ready for landscape planting
• Characteristic leaves developing
• Moderate growth rate
• Full nutrition program

Advanced Germination Techniques

Hormonal Treatments for Germination Enhancement

Gibberellic Acid (GA3):

• Concentration: 300-500 ppm
• Soak time: 24 hours
• 15-20% improvement
• Speeds germination

Smoke Water:

• Limited effect
• Natural seeds germinate well
• 1:100 dilution if used

Bottom Heat:

• Very effective
• 30°C (86°F) soil temperature
• Reduces germination time
• Improves uniformity

4. Cultivation Requirements

Light Requirements

Species-specific Light Tolerance Ranges

• Seedlings (0-2 years): 300-800 μmol/m²/s (70-80% shade)
• Juveniles (2-8 years): 800-1500 μmol/m²/s (50-60% shade)
• Sub-adults (8-15 years): 1500-2000 μmol/m²/s (30% shade to full sun)
• Adults: Full sun preferred (2000+ μmol/m²/s)

Pioneer species tolerating various light levels.

Seasonal Light Variations and Management

• Adapts to seasonal changes well
• Young plants prefer consistent shade
• Adults thrive in full exposure
• Gradual acclimation important

Artificial Lighting for Indoor Cultivation

• Moderate to high light needed
• Standard grow lights adequate
• 12-14 hour photoperiod
• 300-500 foot-candles minimum

Temperature and Humidity Management

Optimal Temperature Ranges

• Ideal: 24-32°C (75-90°F)
• Acceptable: 18-38°C (64-100°F)
• Minimum survival: 10°C (50°F)
• Maximum tolerance: 42°C (108°F)
• Handles temperature extremes well

Cold Tolerance Thresholds

• Light damage: 13°C (55°F)
• Severe damage: 10°C (50°F)
• Fatal: 5°C (41°F)
• Young plants more sensitive

Hardiness Zone Maps

• USDA Zones: 10a-11
• Marginal in 9b with protection
• Sunset Zones: 22-24, H2
• European: H2-H1b

Humidity Requirements and Modification

• Optimal: 65-85%
• Minimum tolerable: 50%
• Adapts to various humidity
• Benefits from air movement

Soil and Nutrition

Ideal Soil Composition and pH

pH preference: 6.0-7.5 (slightly acidic to neutral)

Adaptable mix:

• 30% quality topsoil
• 25% compost
• 20% perlite
• 15% coconut coir
• 10% coarse sand

Well-draining but moisture-retentive

Nutrient Requirements Through Growth Stages

Seedlings (0-2 years):

• Light feeding after 3 months
• 1/4 strength monthly
• Balanced formulation

Juveniles (2-8 years):

• NPK ratio: 8-4-6
• Monthly during growing season
• Micronutrients important

Adults (8+ years):

• NPK ratio: 12-4-8
• Heavy feeder once established
• Quarterly applications

Organic vs. Synthetic Fertilization

Organic Program:

• Compost mulch excellent
• Aged manure beneficial
• Seaweed extracts for micronutrients
• Palm responds very well

Synthetic Approach:

• Controlled-release ideal
• Palm special formulations
• Regular micronutrient supplements
• Avoid salt buildup

Micronutrient Deficiencies and Corrections

• Magnesium: Common - Epsom salts
• Manganese: Occasional - foliar spray
• Iron: In alkaline soils - chelated iron
• Boron: Rare - borax application

Water Management

Irrigation Frequency and Methodology

• Moderate to high water needs
• Consistent moisture preferred
• Deep watering beneficial
• Increase during growth

Drought Tolerance Assessment

• Moderate drought tolerance
• Established plants resilient
• Stilt roots help stability
• Recovery generally good

Water Quality Considerations

• Tolerates various water sources
• Not particularly salt sensitive
• pH 6.0-7.5 acceptable
• Avoid very hard water

Drainage Requirements

• Good drainage essential
• Cannot tolerate waterlogging
• Raised planting in heavy soils
• Mulch beneficial

5. Diseases and Pests

Common Problems in Growing

• Scale insects: Most common issue
• Palm aphids: On new growth
• Leaf spots: In high humidity
• Root rot: Poor drainage

Identification of Diseases and Pests

Insect Pests:

• Coconut scale: White masses
• Palm aphids: Distorted new growth
• Mealybugs: In crownshaft
• Red palm mite: Bronzing of leaves

Diseases:

• Pestalotiopsis leaf spots
• Phytophthora root rot
• Ganoderma butt rot (older palms)
• Generally healthy species

Environmental and Chemical Protection Methods

Cultural Controls:

• Good air circulation
• Proper drainage paramount
• Remove infected fronds
• Maintain plant vigor

Chemical Options:

• Horticultural oil for scales
• Systemic insecticides if severe
• Copper fungicides preventatively
• Minimal chemical use preferred

6. Indoor Palm Growing

Specific Care in Housing Conditions

Indoor Challenges:

• High light requirements
• Ultimate size consideration
• Stilt roots need space
• Humidity needs moderate

Success Factors:

• Brightest location possible
• Large containers essential
• Regular feeding program
• Air circulation important

Replanting and Wintering

Replanting Schedule:

• Young plants: Every 1-2 years
• Mature plants: Every 3-4 years
• Spring timing optimal

Replanting Process:

1. Choose larger container
2. Maintain root ball integrity
3. Fresh, well-draining medium
4. Support if needed
5. Water thoroughly

Winter Care:

• Maintain above 15°C (59°F)
• Reduce watering 30%
• Monthly light feeding
• Maximum light exposure
• Monitor for pests

7. Landscape and Outdoor Cultivation

Garden Impact

• Spectacular stilt roots
• Bronze new leaves stunning
• Tropical focal point
• Conservation value

Design Applications

• Specimen plantings
• Tropical gardens
• Slope stabilization
• Coastal gardens (protected)

8. Cold Climate Cultivation Strategies

Cold Hardiness

Limited cold tolerance but better than many tropical palms.

Winter Protection

• Protection below 15°C (59°F)
• Can survive brief 10°C (50°F)
• Young plants need more protection
• Wind protection essential

Hardiness Zone

• USDA 10a-11 standard
• Zone 9b possible in protected sites
• Mediterranean climates marginal

Winter Protection Systems and Materials

Marginal Areas:

• Trunk wrapping helpful
• Protect stilt roots
• Overhead coverage
• Heat source ready

Container Culture:

• Move to protection
• Reduce watering
• Maintain humidity
• Monitor temperatures

Establishment and Maintenance in Landscapes

Planting Techniques for Success

Site Selection:

• Full sun to part shade
• Protection from strong winds
• Well-draining location
• Room for stilt roots

Soil Preparation:

• Dig large planting hole
• Amend with organics
• Ensure drainage
• Create water basin

Planting Process:

1. Plant at same depth
2. Support if needed
3. Water deeply
4. Mulch immediately

Long-term Maintenance Schedules

Monthly (Growing Season):

• Deep watering as needed
• Fertilizer application
• Pest monitoring
• New growth inspection

Quarterly:

• Comprehensive feeding
• Pruning dead fronds only
• Stilt root inspection
• Photo documentation

Annually:

• Soil testing
• Mulch renewal
• Support adjustment
• Health assessment

Special Considerations:

• Protect developing stilt roots
• Never damage growing point
• Allow natural lean
• Document for conservation