Clusterspike False Indigo vs Common Oak Fern

Amorpha crenulata compared with Gymnocarpium dryopteris

Taxonomic Classification

Rank	Clusterspike False Indigo	Common Oak Fern
Kingdom same	Plantae (Plants)	Plantae (Plants)
Phylum	Magnoliophyta (Flowering Plants)	Tracheophyta
Class	Magnoliopsida (Dicots)	Polypodiopsida (Polypodiopsida)
Order	Fabales (Legumes & Allies)	Polypodiales (Polypodiales)
Family	Fabaceae	Cystopteridaceae
Genus	Amorpha	Gymnocarpium
Species	Amorpha crenulata	Gymnocarpium dryopteris

Evolutionary Relationship

Clusterspike False Indigo and Common Oak Fern share a common ancestor at the Kingdom level: Plantae. (Plants)

Conservation Status

Clusterspike False Indigo

CR — Critically Endangered

Common Oak Fern

CR — Critically Endangered

Physical Characteristics

Attribute	Clusterspike False Indigo	Common Oak Fern
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Clusterspike False Indigo

Habitat

Typically found in diverse terrestrial habitats from tropical forests to temperate regions.

Common Oak Fern

Habitat

Found across multiple habitat types including temperate broadleaf and mixed forests, temperate coniferous forests, and boreal forests and taiga, among 4 distinct biome types within the Palearctic biogeographic realm. Populations are also found in montane and highland environments at higher elevations.

Range

Found across Europe (6 countries) and North America (Canada, United States). Currently classified as Critically Endangered on the IUCN Red List, this species faces significant conservation challenges across its range.

Clusterspike False Indigo

Amorpha crenulata, known as clusterspike false indigo or crenulate lead plant, is a critically endangered flowering shrub in the family Fabaceae with a highly restricted distribution confined to Miami-Dade County in southern Florida, USA. This species represents one of North America's rarest plants, with remaining populations numbering in the hundreds of individuals occurring in pine rockland habitat, an ecosystem itself ranked among the most imperiled in the United States. Pine rocklands are fire-dependent communities on exposed oolitic limestone, characterized by an open canopy of slash pine over diverse understory, and have been reduced to less than two percent of their historical extent by urban development in the Miami metropolitan area. Amorpha crenulata produces elongated spikes of small purple flowers typical of the genus and was historically more widespread across the Miami Rock Ridge before land development eliminated most habitat. Current populations exist primarily within Everglades National Park and a few private preserves. Its Critically Endangered status reflects the tiny remaining population, extreme habitat restriction, ongoing threats from urbanization, altered fire regimes, and sea-level rise that threatens low-elevation limestone habitats. Conservation efforts focus on habitat protection, controlled burning to maintain pine rockland structure, and ex situ seed banking.

Common Oak Fern

<em>Gymnocarpium dryopteris</em>, the common oak fern, is a delicate terrestrial fern in the family Cystopteridaceae (or Woodsiaceae, depending on classification). Despite its common name, the species is not specifically associated with oak trees; rather, it typically grows in cool, moist, shaded environments including boreal and mixed forests, rocky woodland slopes, stream banks, and shaded cliff faces. <em>Gymnocarpium dryopteris</em> spreads by rhizomes and forms low, spreading colonies with characteristic triangular, three-pinnate fronds that emerge from a slender creeping rootstock. Its geographic range spans Europe and North America, with populations in cool temperate and boreal zones. The species is currently assessed as Critically Endangered in certain regional assessments, suggesting that particular populations face severe decline, likely due to habitat loss, forest fragmentation, and altered hydrology, even if the species retains a broader global range. Biological traits such as lifespan, body size, and diet remain poorly documented at a standardized population level. <em>Gymnocarpium dryopteris</em> is a characteristic indicator of undisturbed cool woodland habitats and is valued for both its ecological role in forest understoreys and its aesthetic appeal.