The Good, the Bad, and the Banyan: Ficus Species in Hawai‘i
Posted on Nov. 17, 2025 / Plant Pests, Arboriculture, Parks, Beneficial insects / Subscribe 0
By: Chuck Chimera
With their sprawling canopies, pillar-like trunks, and serpentine roots cascading over rock walls and ruins, banyan trees (genus Ficus) evoke a sense of ancient, primal power. They are living embodiments of nature’s slow, inevitable reclamation of civilization's footprints. This captivating beauty has made them landscaping favorites throughout the tropics, including the Hawaiian Islands, which, despite having no native banyans, now host at least 60 of the world's 800+ Ficus species.
However, recent tragic events—from the 2023 Lahaina fire to a fatal tree collapse in Hilo—have thrust these giants into the spotlight. Their stories reveal a complex duality: some banyans are cherished living landmarks, while others have become invasive forces, damaging Hawaiʻi's fragile ecosystems and infrastructure.
The Key to Invasion: A Tiny, Specialized Wasp
To understand this duality, one must first appreciate the banyan's unique reproductive strategy. Ficus trees have one of the most specialized pollination systems in the plant kingdom, relying on an obligate mutualism with tiny gall wasps (family Agaonidae). Each Ficus species is typically pollinated by a single, specific wasp species.
Here’s how it works: A female wasp enters the enclosed fig inflorescence (a syconium), pollinates the internal flowers, and lays her eggs. Her larvae develop inside, and once mature, the wingless males mate with the females and die after chewing exit tunnels. The new generation of females, now dusted with pollen, emerges to find a new fig, continuing the cycle. Without its specific pollinator, a banyan tree cannot produce viable seeds and must be propagated by cuttings.
Figure 1: Agaonid wasps emerging from the receptacle (fruiting body) of Ficus. Photo credit: Alan Manson (Wikimedia Commons)
This biological lock-and-key system is the crux of the issue in Hawaiʻi. The islands have no native Ficus and, crucially, no native pollinator wasps.
The Exception to the Rule: The Common Fig
This intricate pollination system, however, has a notable and delicious exception: the Common Fig (Ficus carica). Unlike their relatives, the commonly cultivated varieties of F. carica do not require pollination to produce edible fruit. The figs develop parthenocarpically—meaning without fertilization—allowing trees to fruit successfully in regions where the pollinating wasp is absent. This is why the popular variety ‘Brown Turkey’ thrives in backyards and farms across Hawaiʻi and the continental U.S., providing a reliable harvest without any risk of the invasive seeding that plagues other fig or banyan species.
Unlocking the Problem: A Well-Intentioned Mistake
In the early 20th century, H. L. Lyon of the Hawaiian Sugar Planters' Association launched a massive reforestation effort to restore watersheds devastated by clearing, overgrazing from feral ungulates, and erosion. Among the many planting choices, he selected several Ficus species largely because they lacked commercial timber value and would be left standing to protect watersheds. Between 1910 and 1960, approximately 129,000 Ficus trees (from at least 35 species) were planted across the islands.
To ensure these trees could reproduce, four species of pollinating fig wasps were deliberately introduced between 1909 and 1938. This single act unlocked the reproductive potential of several banyan species, setting the stage for their eventual spread.
The Consequences: Stranglers in the Forest
Of the introduced pollinators, three associated Ficus species—F. microcarpa (Chinese banyan), F. macrophylla (Moreton Bay fig), and F. rubiginosa (Port Jackson fig)—are now naturalized. At least three others have joined them (F. nota, F. platypoda, and F. religiosa), and two more are potential invaders (F. glandifera, and F. pumila), indicating that their pollinator wasps are also established in the islands.
The most significant ecological threat comes from the "strangler figs." Species like F. macrophylla and F. microcarpa are hemiepiphytes, beginning life high in the canopy of a host tree. They send aerial roots down to the soil, eventually forming a lattice that envelops and outcompetes their support. The host tree often dies, leaving the banyan standing on its own root cage.
Insert Photo 2. Strangling aerial roots of Chinese banyan, typical of many hemiepiphytic Ficus species. Photo credit: Forest and Kim Starr
This tragedy is unfolding in real-time at Kalōpā State Park on Hawaiʻi Island. Non-native birds disperse Moreton Bay fig seeds into the canopies of native ʻōhiʻa (Metrosideros polymorpha) trees. The resulting strangler figs accelerate the decline of these native giants, which are already ravaged by Rapid ʻŌhiʻa Death disease, sometimes toppling them under the sheer weight of the invading banyan.
Figure 3. Moreton Bay fig strangling a native ʻōhiʻa tree at Kalōpā State Park. Photo credit: Chuck Chimera
The impacts extend beyond the forest. The aggressive roots of invasive banyans damage old irrigation systems, cultural sites like heiau (temples) and fishponds, and other native trees like koa (Acacia koa). The human cost was starkly illustrated in Hilo in July 2025, when a massive Chinese banyan fell without warning, killing two people and causing extensive damage to power lines and a nearby chapel.
A Hopeful Exception: The Indian Banyan
Amid these challenges, one species stands out as a safe and majestic exception: Ficus benghalensis, the Indian banyan. Because its specific pollinator wasp was never introduced in the Hawaiian Islands, it cannot produce viable seeds and remains a non-invasive landscaping choice, a fact that is also true of the other non-naturalized Ficus species.
Renowned for its immense size—legend claims Alexander the Great’s army once sheltered beneath a single tree— the Indian banyan is perfectly suited for expansive public spaces. In Hawaiʻi, magnificent specimens grace locations like Kapiʻolani Park, ʻIolani Palace, and the historic courthouse square in Lahaina.
Figure 4. Indian banyan in Lahaina Maui, prior to the August 2023 fire. Photo credit: Forest and Kim Starr
The Lahaina tree’s story is now one of profound symbolism. After the horrific 2023 fire, it was feared this iconic landmark would succumb to its traumatic injuries. Yet, thanks to the tree’s resilience and the tireless care of arborists and volunteers, it has shown dramatic signs of recovery. In the ensuing two years, it has become a living symbol of hope and restoration for many in the Maui community. Its survival is now being honored with the planting of culturally significant native trees, canoe plants, and other ornamentals in the surrounding area.
A Legacy of Duality
The story of banyans in Hawaiʻi is a powerful lesson in ecological interdependence. The deliberate introduction of tiny wasps transformed several of these landscape icons into agents of ecological change. Today, they exist on a spectrum: species with their pollinators can become invasive stranglers, while those without, like the Indian banyan, remain benign symbols of resilience.
This duality underscores the importance of mindful plant selection. By choosing non-invasive species, we can enjoy the awe-inspiring beauty of banyans without sacrificing the health of Hawaiʻi’s unique native ecosystems.
For help selecting non-invasive plants and identifying invasive species like some Ficus trees in Hawaiʻi, visit the Plant Pono website.
Chuck Chimera is a weed risk assessment specialist with the Hawaii Invasive Species Council.
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