North America Native Plant

Giant Cowbane

Botanical name: Oxypolis greenmanii

USDA symbol: OXGR5

Life cycle: perennial

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Oxypolis filiformis (Walter) Britton ssp. greenmanii (Mathias & Constance) W.S. Judd (OXFIG)   

Giant Cowbane: A Rare Florida Native Worth Protecting Meet giant cowbane (Oxypolis greenmanii), a distinctive perennial wildflower that’s as unique as it is uncommon. This Florida endemic belongs to the carrot family and represents one of nature’s more specialized creations – a plant so perfectly adapted to its wetland home ...

Rare plant alert!

Region: Conservation status by state

Status: S3: Status is uncertain but is somewhere between the following rankings: Vulnerable: Either very rare and local throughout its range, found only in a restricted range (even if abundant at some locations), or factors are making it vulnerable to extinction. Typically 21 to 100 occurrences or between 3,000 and 10,000 individuals ⚘

Giant Cowbane: A Rare Florida Native Worth Protecting

Meet giant cowbane (Oxypolis greenmanii), a distinctive perennial wildflower that’s as unique as it is uncommon. This Florida endemic belongs to the carrot family and represents one of nature’s more specialized creations – a plant so perfectly adapted to its wetland home that it’s found nowhere else in the world except the Sunshine State.

What Makes Giant Cowbane Special?

Giant cowbane is a herbaceous perennial forb, meaning it’s a non-woody plant that dies back each winter and returns the following spring. Despite its somewhat ominous common name (which it shares with several related species), this native beauty produces delicate white flowers arranged in umbrella-like clusters called umbels – a hallmark of the carrot family.

The plant typically grows as an upright specimen, making it an excellent choice for adding vertical interest to wetland gardens and naturalized areas.

A True Florida Original

This remarkable plant is found exclusively in Florida, making it a true endemic species. Its limited distribution contributes to its vulnerable conservation status, with botanists classifying it as S3 (Vulnerable) globally. This means giant cowbane faces potential threats and exists in relatively few locations with limited populations.

Important Conservation Considerations

Before you consider adding giant cowbane to your garden, please note its rare status. With only an estimated 3,000 to 10,000 individuals remaining in the wild, this plant requires our protection. If you’re interested in growing giant cowbane, only source plants or seeds from reputable native plant nurseries that practice ethical propagation methods. Never collect from wild populations.

Garden Appeal and Landscape Uses

For Florida gardeners lucky enough to find responsibly sourced giant cowbane, this plant offers several appealing qualities:

  • Delicate white umbel flowers that attract pollinators
  • Upright growth habit perfect for wetland gardens
  • Authentic Florida heritage – it doesn’t get more local than this!
  • Excellent for rain gardens and bioswales
  • Supports native ecosystem relationships

Growing Conditions and Care

Giant cowbane is adapted to Florida’s wetland environments, so successful cultivation requires mimicking these conditions:

  • Moisture: Consistently wet to saturated soils – think bog garden conditions
  • Sunlight: Full sun to partial shade
  • Climate: USDA zones 8-10 (naturally suited to Florida’s climate)
  • Soil: Wet, organic-rich soils typical of marshes and wetland edges

Pollinator and Wildlife Benefits

Like other members of the carrot family, giant cowbane serves as an important pollinator plant. Its umbrella-shaped flower clusters provide easy landing platforms for various insects, including native bees, beneficial wasps, flies, and butterflies. By supporting these pollinators, the plant plays a crucial role in maintaining Florida’s native ecosystem balance.

Is Giant Cowbane Right for Your Garden?

Giant cowbane is an excellent choice for Florida gardeners who:

  • Have consistently wet areas in their landscape
  • Are creating rain gardens or bioswales
  • Want to support native pollinators
  • Are passionate about growing rare and unique native plants
  • Can source plants responsibly from ethical nurseries

However, this plant may not be suitable if you have well-drained soils or can’t maintain consistently moist conditions.

Planting and Care Tips

Successfully growing giant cowbane requires attention to its specific needs:

  • Plant in spring after the last frost
  • Ensure soil remains consistently moist to wet year-round
  • Mulch around plants to help retain moisture
  • Allow plants to go to seed to support local populations (if space permits)
  • Avoid fertilizers – native wetland plants prefer lean conditions
  • Be patient – perennial natives often take time to establish

A Plant Worth Protecting

Giant cowbane represents something special in the plant world – a rare endemic that tells the story of Florida’s unique natural heritage. While its vulnerable status means we must be thoughtful about cultivation, responsible gardening with this species can actually help conservation efforts by maintaining genetic diversity and reducing pressure on wild populations.

If you’re drawn to rare native plants and have the right growing conditions, giant cowbane could be a meaningful addition to your Florida landscape. Just remember to source responsibly and consider yourself a steward of this remarkable species.

Giant Cowbane

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Rosidae

Order

Apiales

Family

Apiaceae Lindl. - Carrot family

Genus

Oxypolis Raf. - cowbane

Species

Oxypolis greenmanii Mathias & Constance - giant cowbane

Plant data source: USDA, NRCS 2025. The PLANTS Database. https://plants.usda.gov,. 2/25/2025. National Plant Data Team, Greensboro, NC USA