Puerto Rican Hat Palm

Scientific name: Sabal causiarum

IUCN Red List threat level: Vulnerable

GPS Location: 17° 42′ 58.37″ N, 64° 49′ 47.51″ W

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Observations:

Phenology Markers – Puerto Rican Hat Palm (Sabal causiarum)

Common Name: Puerto Rican Hat Palm, Puerto Rican Sabal
Scientific Name: Sabal causiarum
Family: Arecaceae (Palm family)
Native Range: Puerto Rico, U.S. Virgin Islands, Hispaniola
Habitat: Dry limestone hills, coastal plains, and rocky scrub

General Description:

Sabal causiarum is a large, single-stemmed, fan-leaved palm native to the Greater Antilles. It is known for its massive, columnar trunk, rounded canopy of palmate leaves, and long lifespan. Historically used for thatch and weaving, it remains culturally significant across the Caribbean. While palms are monocots and do not form true wood, this species develops substantial height and mass, making it one of the few native palms that can be counted as a tree in arboretum contexts — especially when mature.

Phenological Markers:

1. Leaf Growth and Senescence:

  • New Leaf Emergence: Year-round, with peaks in the wet season (May – October)
  • Leaf Maturity: Each frond matures in 4–6 weeks
  • Leaf Senescence: Older fronds naturally die and hang down or detach (can be pruned)
  • Leaf Characteristics: Large, fan-shaped fronds up to 6–8 feet across; pale green to blue-green; arranged in a spiral at the crown

2. Flowering Period:

  • First Sign of Inflorescence: Early summer (May – June)
  • Peak Bloom: Summer (June – August)
  • End of Flowering: Late summer to early fall (September)
  • Flower Characteristics: Long, arching inflorescences emerge from among the leaves; bearing hundreds of small, cream-colored flowers

3. Fruit Production:

  • First Sign of Fruit Development: Late summer (August – September)
  • Fruit Maturity: Fall to early winter (October – December)
  • End of Fruiting: Late winter (January)
  • Fruit Characteristics: Small, round, blackish drupes (about 1 cm in diameter); each contains a single seed; often persistent on the tree for several months

4. Dormancy Period:

  • Dormancy Begins: Minimal in tropical climates; slight reduction in growth during dry season (January – March)
  • Dormancy Ends: Spring (April), with rainfall and warmer temperatures triggering new leaf flush

Ecological Notes:

  • Pollinators: Small bees, flies, and wind
  • Wildlife Interaction: Fruits are consumed by birds and small mammals; the canopy provides habitat for nesting and shade
  • Soil Preferences: Limestone-rich, sandy, or rocky soils with good drainage
  • Growth Habit: Solitary trunk, 20–60 ft tall; base may be swollen in older trees; extremely wind- and salt-tolerant

Observational Guidelines:

  • Best Time for Observation: May through December for flowering and fruiting cycles
  • Key Observation Features:
    • Trunk diameter and height (for arboretum records)
    • Crown shape and frond coloration
    • Inflorescence emergence and flowering stage
    • Fruit development and drop
  • Phenology Triggers: Seasonal rains initiate inflorescence production; prolonged dry spells reduce activity

ArbNet Qualification Notes:

Sabal causiarum qualifies as a native canopy tree for ArbNet purposes when:
– Specimen is ground-planted and mature
– Exhibits trunk height over 15 ft
– Used as part of native habitat restoration or botanical collection
– Properly documented with ID tags and phenology records

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