1. Introduction

Habitat and Distribution, Native Continent

Pholidocarpus kingianus is endemic to the southern Thai provinces and northern Peninsular Malaysia, with populations concentrated in Narathiwat and Yala provinces of Thailand, and Kelantan, Terengganu, and northern Pahang states of Malaysia. This magnificent palm inhabits lowland and hill dipterocarp forests from sea level to 800 meters elevation, with highest densities between 200-500 meters. It shows a strong preference for alluvial soils along rivers and streams, often forming impressive groves in seasonally flooded areas. The species thrives in areas with annual rainfall of 2,000-3,000mm, relatively evenly distributed throughout the year with a brief drier period. These palms are typically found in the transition zone between swamp forest and dryland forest, where they can dominate the understory.

Taxonomic Classification and Scientific Classification

Synonyms

• Iguanura kingiana Becc. (basionym, 1886)
• Pholidocarpus kingii Ridl. (orthographic variant)
• Pholidocarpus angustifolius Becc. (misapplied)

Common Names

• King's pholidocarpus (English)
• Giant iguanura palm (English - historical)
• Kepau (Malay)
• Palas gajah (Malay - "elephant palm")
• ปาล์มพญานาค (Thai - "palm phaya nak")
• 金氏鳞果椰 (Chinese)

Expansion in the World

Pholidocarpus kingianus has very limited presence in cultivation:

• Singapore Botanic Gardens (mature specimen grove)
• Bogor Botanical Gardens, Indonesia
• A few private collections in Southeast Asia
• Virtually unknown in Western cultivation
• Seeds rarely available internationally
• No commercial production
• IUCN Red List status: Vulnerable

The rarity in cultivation reflects both limited seed availability and the massive size these palms attain, making them suitable only for large tropical gardens.

2. Biology and Physiology

Morphology

Trunk

P. kingianus develops a massive, solitary trunk reaching 20-35 meters in height with a diameter of 30-60cm, making it one of the largest palms in Southeast Asia. The trunk is dark gray to brown, closely ringed with prominent leaf scars. A distinctive feature is the covering of persistent, dark brown to black fibrous leaf bases on the upper portion, creating a shaggy appearance. The trunk base often shows buttressing in older specimens, particularly those in flood-prone areas.

Leaves

The crown is extraordinary, consisting of 20-40 massive palmate leaves forming a dense, spherical canopy. Individual leaves are among the largest in the palm family, with blades measuring 3-5 meters across. The petiole is 3-4 meters long, armed with fearsome curved black spines up to 5cm long along the margins. The blade is divided into 60-90 segments, each up to 1.5 meters long, creating a majestic fan. Leaves are dark glossy green above, lighter beneath with brownish scales. The costa (extension of petiole into blade) is prominent, extending 1-2 meters into the leaf.

Flower Systems

P. kingianus is hermaphroditic with massive interfoliar inflorescences. The branched inflorescence can reach 2-3 meters long, emerging from among the leaves. The peduncle and rachis are covered in brown scales. Flowers are borne in clusters along the rachillae, each flower small (4-5mm) but numerous. Individual flowers are cream to pale yellow, fragrant, with 6 stamens and a 3-carpellate pistil. Flowering occurs annually in mature specimens, typically during the transition between seasons.

Life Cycle

P. kingianus has an extended life cycle spanning 150-200 years:

• Germination to Seedling (0-5 years): Slow establishment phase
• Juvenile Phase (5-25 years): Trunk development begins
• Sub-adult Phase (25-50 years): Rapid vertical growth
• Adult Phase (50-150 years): Full canopy development and reproduction
• Senescent Phase (150-200 years): Gradual decline

First flowering typically occurs at 30-40 years when the palm reaches 10-15 meters height.

Specific Adaptations to Climate Conditions

• Flood Tolerance: Buttressed base and adventitious roots
• Spine Armature: Protection from large herbivores
• Massive Leaves: Maximum light capture in forest gaps
• Flexible Segments: Wind resistance
• Scale Coverage: Protection from epiphyte loading
• Deep Taproot: Stability and drought access

3. Reproduction and Propagation

Seed Reproduction

Seed Morphology and Diversity

P. kingianus produces large, distinctive fruits covered in overlapping scales (hence "Pholidocarpus" = scale fruit). Fruits are globose to ovoid, 5-8cm diameter, making them among the largest in the genus. The numerous scales are reddish-brown to dark brown, hard and woody, arranged in spiral rows. Each fruit contains 1-3 seeds (typically 1). Seeds are globose to ellipsoid, 3-4cm diameter, with homogeneous endosperm and a large lateral embryo. Fresh seed weight ranges from 15-30 grams. Significant variation exists in fruit size between populations.

Detailed Seed Collection and Viability Testing

Collection Strategy:

• Fruits ripen December-March in most areas
• Collect when scales begin separating
• Climbing required for fresh fruits
• Ground collection possible but lower viability

Viability Assessment:

• Float test: Viable seeds sink
• Weight: Heavier seeds more viable
• Firmness: Soft seeds are dead
• Fresh viability: 85-95%
• One month storage: 60-70%
• Three months: 30-40%
• Six months: <15%

Pre-germination Treatments

Scale Removal:

• Soak fruits 5-7 days
• Remove scales completely
• Clean thoroughly
• Some scales extremely persistent

Scarification:

• File through hard endocarp
• Focus on hilar region
• Hot water soak: 65°C for 30 minutes
• 40-50% improvement noted

Seed Priming:

• Soak scarified seeds 3-5 days
• Change water daily
• Seeds should swell noticeably

Step-by-step Germination Techniques

1. Container: Large individual pots (30cm+ deep)
2. Medium: 40% coarse sand, 30% coconut coir, 20% rice hulls, 10% compost
3. Planting: 5-8cm deep, horizontal position
4. Temperature: 28-32°C (82-90°F) optimal
5. Humidity: 75-85%
6. Light: Deep shade initially
7. Moisture: Consistently moist

Germination Difficulty

Moderate to difficult. Main challenges:

• Large seed size requires space
• Long germination period
• Irregular germination
• Temperature sensitivity

Germination Time

• First emergence: 90-180 days
• Peak germination: 180-300 days
• Complete process: up to 500 days
• Success rate: 40-70% typical

Seedling Care and Early Development

Year 1:

• Maintain high humidity
• Deep shade essential (90%)
• No fertilization needed
• Growth very slow

Years 2-3:

• Begin monthly feeding
• Large containers needed
• Gradually reduce shade
• Spines begin developing

Years 4-5:

• Can plant in ground
• Regular fertilization
• 70% shade still needed

Advanced Germination Techniques

Hormonal Treatments for Germination Enhancement

Gibberellic Acid (GA3):

• Concentration: 1000-1500 ppm
• Injection into seed beneficial
• 72-hour soak after scarification
• 30-40% improvement

Smoke Water Treatment:

• Effective for this species
• 1:50 dilution
• 48-hour treatment
• Breaks dormancy

Combined Protocol:

• Scarification + smoke + GA3
• Sequential treatment
• Can achieve 80% germination
• Reduces time by 30%

4. Cultivation Requirements

Light Requirements

Species-specific Light Tolerance Ranges

• Seedlings (0-5 years): 200-500 μmol/m²/s (80-90% shade)
• Juveniles (5-15 years): 500-1000 μmol/m²/s (70-80% shade)
• Sub-adults (15-30 years): 1000-1500 μmol/m²/s (50-60% shade)
• Adults: Can tolerate full sun but prefer partial shade

Seasonal Light Variations and Management

• Young plants need consistent shade
• Adults handle seasonal variations
• Protect from intense afternoon sun
• Forest edge conditions ideal

Artificial Lighting for Indoor Cultivation

• Not suitable for indoor growth (size)
• Seedlings only temporarily
• High output lights needed
• Natural light essential long-term

Temperature and Humidity Management

Optimal Temperature Ranges

• Ideal: 25-32°C (77-90°F)
• Acceptable: 20-35°C (68-95°F)
• Minimum survival: 15°C (59°F)
• Maximum tolerance: 40°C (104°F)
• Consistent warmth preferred

Cold Tolerance Thresholds

• Damage threshold: 18°C (64°F)
• Severe damage: 15°C (59°F)
• Fatal: 10°C (50°F)
• No frost tolerance

Hardiness Zone Maps

• USDA Zones: 10b-11
• Marginal in 10a
• Sunset Zones: 23-24
• European: H1a

Humidity Requirements and Modification

• Optimal: 70-85%
• Minimum: 60%
• High humidity benefits growth
• Tolerates lower humidity when mature

Soil and Nutrition

Ideal Soil Composition and pH

• pH preference: 5.5-7.0
• Alluvial soil mix: 30% loamy topsoil, 25% coarse sand, 20% aged compost, 15% coconut coir, 10% rice hulls
• Rich, moisture-retentive but draining

Nutrient Requirements Through Growth Stages

Seedlings (0-5 years):

• Light feeding after year 1
• 1/4 strength monthly
• Balanced formulation

Juveniles (5-15 years):

• NPK ratio: 3-1-2
• Monthly application
• Increase gradually

Adults (15+ years):

• NPK ratio: 15-5-10
• Heavy feeders
• Quarterly application
• Large quantities needed

Organic vs. Synthetic Fertilization

Organic Program:

• Aged manure excellent
• Compost mulch thick
• Palm special organic blends
• Slow-release preferred

Synthetic Approach:

• High-analysis fertilizers
• Controlled-release for convenience
• Supplement with organics
• Watch for salt buildup

Micronutrient Deficiencies and Corrections

• Magnesium: Common - Epsom salts
• Manganese: Frizzletop - foliar spray
• Iron: Yellowing - chelated iron
• Boron: Growing point issues

Water Management

Irrigation Frequency and Methodology

• High water requirements
• Deep, frequent watering
• Can tolerate waterlogging
• Increase in dry periods

Drought Tolerance Assessment

• Moderate drought tolerance when mature
• Juveniles vulnerable
• Wilting occurs slowly
• Recovery generally good

Water Quality Considerations

• Tolerates various water sources
• Not salt sensitive
• pH 6-7.5 acceptable
• Avoid very hard water

Drainage Requirements

• Good drainage preferred
• Tolerates seasonal flooding
• Avoid permanent waterlogging
• Raised planting in heavy soils

5. Diseases and Pests

Common Problems in Growing

• Leaf spots: Various fungi
• Scale insects: On rachis
• Nutrient deficiencies: Common
• Root rot: In poor drainage

Identification of Diseases and Pests

Fungal Diseases:

• Pestalotiopsis leaf spots
• Colletotrichum anthracnose
• Ganoderma butt rot in old palms
• Phytophthora in waterlogged soil

Pest Issues:

• Rhinoceros beetle: Serious threat
• Palm weevils: Bore into trunk
• Scale insects: Various species
• Bagworms: Defoliate segments

Environmental and Chemical Protection Methods

Cultural Control:

• Good sanitation crucial
• Remove dead fronds promptly
• Improve air circulation
• Proper nutrition prevents issues

Chemical Options:

• Systemic insecticides for borers
• Fungicides for persistent spots
• Neem oil for minor pests
• Professional treatment for beetles

6. Indoor Palm Growing

Specific Care in Housing Conditions

Replanting and Wintering

Container Culture (temporary only):

• Annual repotting when young
• Massive containers eventually
• Not practical long-term
• Ground planting essential

Winter Care (tropical only):

• No special requirements
• Maintain normal care
• Watch for cool damage
• Protect from winds

7. Landscape and Outdoor Cultivation

Landscape Impact

• Majestic specimen tree
• Park or estate scale only
• Tropical garden centerpiece
• Not for small gardens

Design Applications

• Large lawn specimen
• Botanical gardens
• Resort landscaping
• Conservation collections

8. Cold Climate Cultivation Strategies

Cold Hardiness

Minimal cold tolerance - strictly tropical.

Winter Protection

Not possible outdoors in cold climates

• Conservatory only option
• Minimum 15°C (59°F) required
• High humidity needed

Hardiness Zone

• USDA 10b-11 only
• Not suitable below Zone 10b
• Tropical greenhouse required elsewhere

Winter Protection Systems and Materials

Only viable in heated conservatories with:

• Tropical temperatures year-round
• High ceilings (eventual 35m height)
• Professional maintenance
• Substantial investment

Establishment and Maintenance in Landscapes

Planting Techniques for Success

Site Selection:

• Large open space required
• Consider 35m ultimate height
• Away from structures
• Partial shade when young

Soil Preparation:

• Deep cultivation
• Rich amendments
• Ensure drainage
• Large planting hole

Installation:

• Plant in wet season
• Stake securely
• Immediate mulching
• Temporary shade structure

Long-term Maintenance Schedules

Monthly:

• Inspection for pests
• Remove dead fronds
• Check for deficiencies

Quarterly:

• Heavy fertilization
• Deep watering
• Mulch renewal

Annually:

• Professional inspection
• Pruning equipment needed
• Safety assessment
• Growth documentation

Special Considerations:

• Professional maintenance required
• Safety equipment for pruning
• Consider liability (spines)
• Long-term commitment