Clusterspike False Indigo vs Common Milkwort

Amorpha crenulata compared with Polygala vulgaris

Key Differences

• Clusterspike False Indigo is Critically Endangered while Common Milkwort is Vulnerable.

Taxonomic Classification

Rank	Clusterspike False Indigo	Common Milkwort
Kingdom same	Plantae (Plants)	Plantae (Plants)
Phylum same	Magnoliophyta (Flowering Plants)	Magnoliophyta (Flowering Plants)
Class same	Magnoliopsida (Dicots)	Magnoliopsida (Dicots)
Order same	Fabales (Legumes & Allies)	Fabales (Legumes & Allies)
Family	Fabaceae	Polygalaceae
Genus	Amorpha	Polygala
Species	Amorpha crenulata	Polygala vulgaris

Evolutionary Relationship

Clusterspike False Indigo and Common Milkwort share a common ancestor at the Order level: Fabales. (Legumes & Allies)

Conservation Status

Clusterspike False Indigo

CR — Critically Endangered

Common Milkwort

VU — Vulnerable

Physical Characteristics

Attribute	Clusterspike False Indigo	Common Milkwort
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 Milkwort

Habitat

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

Range

Widely distributed across Europe (6 countries), North America (Canada, United States), and Oceania and the Pacific (Australia). Currently classified as Vulnerable 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 Milkwort

Common Milkwort (<em>Polygala vulgaris</em>) is a small flowering plant in the genus <em>Polygala</em>, family Polygalaceae. It is distributed across Europe, North America, and Oceania, with confirmed presence in countries including Australia, Belgium, Canada, Denmark, and Finland. Typically found in diverse terrestrial habitats ranging from tropical forests to temperate grasslands, this species favors calcareous grasslands, heathlands, and other open, well-drained habitats. Common Milkwort produces small flowers in shades of blue, pink, or white, and is associated with traditional grassland communities. Currently classified as Vulnerable on the IUCN Red List, the species faces significant conservation challenges across its range, likely driven by habitat loss through agricultural intensification and the decline of traditionally managed grasslands. Specific biological measurements such as lifespan, length, and weight are not documented in available records. The genus name <em>Polygala</em> derives from Greek meaning "much milk," reflecting a historical belief that the plant could increase milk production in livestock.