How to Grow Wiliwili, Coral Tree

iNaturalist

Wiliwili, Coral Tree

Erythrina sandwicensis

tree

Erythrina sandwicensis, commonly known as Wiliwili, is a native Hawaiian nitrogen-fixing tree that produces vibrant red-orange flowers and serves as a pioneer species in forest restoration. This deciduous to semi-deciduous tree rapidly colonizes disturbed areas, enriching soil through symbiotic nitrogen fixation via root nodules. It is culturally significant in Hawaii and ecologically valuable for ecosystem rehabilitation.

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Example Wiliwili, Coral Tree timeline · Pittsburgh, PA (Zone 6b)

  1. Plant Wiliwili, Coral Tree

    Around Apr 17

    Near Pittsburgh's average last spring frost.

  2. Tend & protect

    Late spring–summer

    Watering, feeding, and pest-watch reminders.

  3. Harvest Wiliwili, Coral Tree

    Late summer into fall

    Before the first fall frost (≈ Nov 8)

Sample dates for Pittsburgh, PA. Sign up to get exact Wiliwili, Coral Tree dates for your own zip code.

Growing Conditions

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Sun: Full sun, 6+ hours daily; performs best in open, unshaded conditions
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Water: Moderate water needs once established; drought-tolerant. Water deeply during establishment (first 1-2 years), then reduce frequency. Sensitive to waterlogging; ensure good drainage.
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Spacing: 180 inches
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Days to maturity: 2-3 years to flowering; 5-7 years to substantial canopy contribution in restoration
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Planting depth: 1 inch for seeds; transplants at same depth as root ball

Soil

Type: Well-draining sandy loam to volcanic soil; tolerates poor, degraded, or marginal soils
pH: 6.0-7.5
Amendments:
Minimal amendments needed; benefits from inoculation with Rhizobium leguminosarum or appropriate nitrogen-fixing bacteria Compost or aged mulch to improve water retention in very sandy soils Avoid heavy nitrogen fertilizers; relies on biological nitrogen fixation

Growing Zones

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Thrives in USDA zones 10-11; requires tropical to subtropical climates

10a 10b 11a 11b

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Growth Stages

1

Germination & Seedling

3-4 weeks

Seeds sprout within 2-4 weeks; cotyledons emerge with smooth leaves. Seedlings are tender and remain small (2-6 inches) for the first 2-3 months.

Keep soil consistently moist but not waterlogged. Provide partial shade to seedlings to prevent stress. Thin seedlings to strongest individual if direct-seeded.

2

Establishment & Early Growth

6-12 months

Rapid vertical growth phase (12-24 inches/year possible). Nodule formation begins; foliage is bright green and alternate-compound. Young tree becomes woody and develops a central leader.

Establish mulch ring; water regularly during dry spells. Monitor for stem damage and support with staking if in windy locations. Inoculate roots with nitrogen-fixing bacteria if soil lacks natural Rhizobium populations.

3

Vegetative Growth & Root Development

1-3 years

Continued height and canopy expansion; significant increase in trunk diameter. Extensive root system with abundant nitrogen-fixing nodules develops belowground. Foliage remains deciduous or semi-deciduous depending on water availability.

Reduce supplemental water as deep roots establish. Minimal pruning except to remove dead branches or improve form. Nitrogen nodules fix atmospheric nitrogen, reducing external fertilizer needs and benefiting neighboring plants.

4

Flowering & Reproduction

4-8 weeks flowering period; repeat annually once mature

Distinctive spikes of bright red-orange flowers appear, typically in spring/early summer (timing variable in tropics). Flowers attract native birds and insects. Flowering signals maturity for seed production.

No special care needed; maintain established watering schedule. Flowers persist for several weeks; encourage pollinators by avoiding pesticides. Trees can produce viable seeds at 2-3 years of age.

5

Seed Production & Ecological Maturity

Ongoing after year 3; long-term ecological role 10+ years

Long, flattened seed pods develop after flowering, containing 1-6 hard seeds. Mature pods dry and may dehisce naturally. Trees reach full canopy size (20-40 feet) and maximum nitrogen-fixing capacity.

Collect seed pods if seeds are desired for propagation; allow some to fall naturally for wild regeneration. Tree reaches ecological maturity as a pioneer/nurse species, creating microsites for other vegetation through shade and nitrogen enrichment.

Companion Planting

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Plant with:

Native Hawaiian ferns (Sadleria, Microlepia) Santalum paniculatum (Hawaiian sandalwood) Native ohia (Metrosideros polymorpha) Acacia koa Myoporum sandwicense Gossypium tomentosum (Hawaiian cotton) Native understory shrubs and groundcovers

Avoid planting near:

Dense, established canopies that would shade young trees excessively Extremely wet or waterlogged soils Highly competitive invasive grasses (Pennisetum setaceum, Melinus minutiflora) unless being actively removed

Common Pests

  • Monitor for cottony clusters; prune infested branches; spray horticultural oil or insecticidal soap on young trees; encourage natural predators like ladybugs

  • Remove by hand from small trees; spray with insecticidal soap; introduce parasitoid wasps; avoid over-fertilizing with nitrogen

  • Increase humidity; spray foliage with water; apply miticide if severe; predatory mites can provide biological control

  • Remove and destroy gall-infected branches; prune lower branches to improve air circulation; maintain plant vigor; no chemical controls effective; biological controls under research

Uses

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Nitrogen Fixation & Soil Enrichment

Ecological

Through symbiotic association with Rhizobium bacteria in root nodules, Wiliwili fixes atmospheric nitrogen, enriching degraded soils and reducing need for synthetic fertilizers. This pioneer function accelerates ecosystem recovery in restoration projects, creating fertile microsites for subsequent plant establishment. [source]

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Pioneer Species for Forest Restoration

Ecological

Erythrina's rapid growth, drought tolerance, and ability to thrive on marginal lands make it ideal for restoring degraded Hawaiian forests, abandoned agricultural lands, and eroded slopes. It establishes canopy quickly while enriching soil for native understory species. [source]

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Nectar & Habitat for Native Pollinators

Wildlife

Bright red-orange flowers attract native Hawaiian birds (especially nectarivores like apapane and amakihi) and insects. Provides food resources and structural habitat for forest-dependent fauna during establishment phase. [source]

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Cultural & Traditional Significance

Cultural

Wiliwili holds deep cultural meaning in Hawaiian tradition, with seeds historically used for lei, ornaments, and cultural practices. Its striking appearance and native status make it valuable for cultural restoration and community connection to native ecosystems. [source]

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Ornamental Landscape & Shade Tree

Household

The vibrant red-orange flowers and tropical form make Wiliwili an attractive ornamental specimen for tropical gardens and restoration landscapes. Provides excellent shade while adding aesthetic value to residential and public spaces. [source]

Harvest Tips

For seed collection: Allow pods to mature on tree until brown/dry (4-6 months after flowering). Collect by hand or allow pods to drop naturally. Extract hard seeds and scarify or soak in warm water 24 hours before sowing to improve germination. No leaf or flower harvest typically done; tree's primary value is ecological nitrogen fixation and canopy provision in restoration contexts.

Fun Facts

  • 🌱 Wiliwili seeds are buoyant and were historically dispersed across the Pacific by ocean currents, allowing Hawaiian populations to establish naturally; seeds float for weeks due to air-filled tissue.
  • 🌱 The tree is semi-deciduous, often dropping leaves during dry seasons as a drought adaptation, and leafing out rapidly when water becomes available—a key strategy for surviving Hawaiian droughts.
  • 🌱 In traditional Hawaiian culture, Wiliwili seeds were strung into lei and used as ornaments; the bright red color made them highly valued, and the tree is featured in Hawaiian mythology and place names.

Gardening Terms

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