1. Introduction

Habitat and Distribution, Native Continent

Pritchardia hillebrandii 'blue form' is a selected cultivar of P. hillebrandii, originally discovered within the natural populations on Molokai, Hawaii. While the typical species occurs throughout Molokai's northern valleys, the blue forms were first noted in specific populations in Waikolu Valley and on exposed ridges where environmental stress may have contributed to the distinctive coloration. These selections grow in the same habitat as the species—coastal to montane mesic forests from sea level to 600 meters—but often in more exposed locations with higher light intensity and stronger trade winds. The blue coloration appears to be a stable genetic trait that has been preserved and enhanced through selective propagation.

Taxonomic Classification and Scientific Classification

Synonyms

• Sometimes listed as P. hillebrandii 'Glauca'
• P. hillebrandii 'Silver'
• P. hillebrandii var. glauca (invalid name)
• Blue Molokai pritchardia (trade name)

Common Names

• Blue loulu (English)
• Silver-blue Molokai palm (English)
• Blue Hillebrand's pritchardia (English)
• Loulu uliuli (Hawaiian-inspired, not traditional)
• 蓝叶希氏蒲葵 (Chinese)

Expansion in the World

The blue form has rapidly gained popularity:

• Selected and propagated since 1990s
• Premium collections worldwide
• High demand in Hawaii
• California collections (especially Southern California)
• Florida botanical gardens and private collections
• Australia (Queensland) increasingly common
• Commands premium prices
• Limited but increasing availability

The blue form's striking appearance has made it one of the most sought-after Hawaiian palm cultivars.

2. Biology and Physiology

Morphology

Trunk

Trunk: Identical to the typical species in structure, developing a robust trunk 10-20 meters tall and 25-40cm diameter. The gray-brown trunk shows no color differences from the standard form. Growth rate and ultimate size are the same as the species.

Leaves

Leaves: The crown structure matches the species with 25-35 large costapalmate leaves, but the color is dramatically different. Leaf blades show intense silver-blue to blue-gray coloration, particularly pronounced on new growth. The blue color results from an enhanced waxy coating (glaucous bloom) that is significantly thicker than the typical form. This coating is most intense on the upper surface but also affects the lower surface. In optimal conditions with high light, mature leaves can appear almost metallic blue-silver. Leaf size (100-150cm wide) and segmentation remain identical to the species.

Flower Systems

Flower Systems: Flowering characteristics are identical to the species, with large branched inflorescences 100-150cm long emerging among the leaves. Flowers are creamy white to pale yellow, and flowering seasons (March-July) match the typical form. No differences in flower morphology or timing have been observed.

Life Cycle

The blue form shares the same life cycle as the species:

• Germination to Seedling (0-4 years): Blue color visible from first true leaves
• Juvenile Phase (4-12 years): Color intensifies with age
• Sub-adult Phase (12-25 years): Maximum color development
• Adult Phase (25-150 years): Color maintained throughout
• Senescent Phase (150-200 years): May lose some intensity

Blue coloration is evident from the seedling stage, allowing early selection.

Specific Adaptations to Climate Conditions

In addition to standard species adaptations:

• Enhanced UV Protection: Thicker waxy coating
• Heat Reflection: Blue-silver color reduces heat absorption
• Drought Resistance: Waxy coating reduces transpiration
• Light Maximization: Best color in high light environments
• Wind Resistance: Coating protects from desiccation
• Selection Pressure: May represent adaptation to exposed sites

3. Reproduction and Propagation

Seed Reproduction

Seed Morphology and Diversity

Seeds from blue form parents are morphologically identical to the species: globose, 2.5-3cm diameter, with the same golden-yellow fruits. However, genetic analysis suggests the blue trait is heritable, with approximately 60-80% of seedlings from blue parents showing some degree of blue coloration. The intensity varies among offspring, allowing for continued selection.

Detailed Seed Collection and Viability Testing

Collection and viability testing follow species protocols, with additional considerations:

• Select seeds only from the bluest parents
• Document parent palm characteristics
• Maintain separate seed lots
• Label clearly for tracking
• Viability rates match species (90-98% fresh)

Pre-germination Treatments

Identical to the species:

• Complete mesocarp removal
• 5-7 day soak
• Scarification beneficial
• Hot water treatment effective

Step-by-step Germination Techniques

Follow species protocols exactly:

• Same medium and temperatures
• Identical timing expectations
• Blue color visible in first leaves
• Allows early selection

Germination Difficulty

Same as species (easy to moderate), but with selection considerations:

• Germination rate: 70-90%
• Blue offspring: 60-80%
• Intensity varies
• Cull non-blue seedlings if desired

Seedling Care and Early Development

Selection Phase (3-12 months):

• Blue color evident early
• Select strongest blue seedlings
• Maintain higher light for color
• Document color development

Development (1-3 years):

• Provide maximum safe light
• Color intensifies with exposure
• Growth rate matches species
• Premium specimens identified

Advanced Germination Techniques

Hormonal Treatments for Germination Enhancement

Same as species, no special requirements for blue trait.

Selection and Enhancement

• Grow in higher light from early age
• Select only deepest blue specimens
• Consider tissue culture for best forms
• Maintain breeding records

4. Cultivation Requirements

Light Requirements

Species-specific Light Tolerance Ranges

Same zones as species but with color considerations:

• Seedlings: Need brighter light for color (50-60% shade maximum)
• Juveniles: 30-40% shade enhances blue
• Adults: Full sun produces best color

Higher light throughout life maximizes blue coloration.

Seasonal Light Variations and Management

• Maximum sun exposure when possible
• Color fades in too much shade
• Seasonal variation acceptable
• Protect only from extreme heat

Artificial Lighting for Indoor Cultivation

• Requires very high light for color
• Metal halide or intense LED
• 16+ hour photoperiod
• UV supplementation beneficial

Temperature and Humidity Management

Identical to species for all parameters:

• Optimal: 22-30°C (72-86°F)
• Hardiness: USDA 10a-11
• Some reports suggest blue forms slightly more cold-sensitive

Soil and Nutrition

Ideal Soil Composition and pH

Same as species with notes:

• Higher pH may enhance blue color
• Add lime if needed
• Avoid acid fertilizers
• Micronutrients critical for color

Nutrient Requirements Through Growth Stages

Follow species guidelines with modifications:

• Avoid high nitrogen (reduces blue)
• Increase potassium (enhances color)
• Regular micronutrients essential
• Iron can affect coloration

Water Management

Identical to species:

• Moderate to high water needs
• Good drainage essential
• Drought stress may intensify color
• Avoid overwatering

5. Diseases and Pests

Common Problems in Growing

Same susceptibilities as species:

• Palm weevils major threat
• Scale insects common
• Lethal yellowing susceptible
• No unique pest/disease issues

Color-specific issues:

• Shade causes color loss
• Nutritional imbalances affect blue
• Environmental stress may help color

6. Indoor Palm Growing

Specific Care in Housing Conditions

More challenging than typical form:

• Extremely high light needed for color
• Often disappointing indoors
• Conservatory cultivation better
• Supplemental lighting essential

Replanting and Wintering

Same as species with emphasis on:

• Maximum light in winter
• Avoid overfertilizing
• Maintain cool, dry conditions
• Color may fade in winter

7. Landscape and Outdoor Cultivation

Landscape Impact

• Most spectacular Hawaiian palm
• Premium specimen value
• Focal point in any garden
• Color visible from distance

Design Applications

• Specimen placement critical
• Full sun exposure essential
• Contrasts with green palms
• Coastal gardens ideal

8. Cold Climate Cultivation Strategies

Cold Hardiness

Matches species:

• USDA 10a-11
• Some growers report slightly less hardy
• Protection below 10°C

Winter Protection

Standard species protocols:

• May lose color intensity in winter
• Recovers in spring
• Protect young plants

Establishment and Maintenance in Landscapes

Planting Techniques for Success

Critical considerations for color:

Site Selection:

• Maximum sun exposure
• Open, exposed location
• Reflective surfaces nearby help
• Avoid shade at all costs

Soil Preparation:

• Add lime if acidic
• Perfect drainage
• Mineral mulches (enhance blue)
• Avoid heavy organics

Long-term Maintenance Schedules

Focus on maintaining color:

• Regular micronutrients
• Avoid excess nitrogen
• Prune surrounding vegetation
• Document color changes
• Select seeds from best blues