North America Native Plant

Crescent Bugseed

Botanical name: Corispermum navicula

USDA symbol: CONA4

Life cycle: annual

Habit: forb

Native status: Native to the lower 48 states  

Crescent Bugseed: A Rare Colorado Native Worth Protecting If you’ve never heard of crescent bugseed, you’re not alone. This little-known annual wildflower is one of Colorado’s botanical treasures – and unfortunately, one of its rarest plants. While most native plant enthusiasts are eager to add local species to their gardens, ...

Rare plant alert!

Region: Conservation status by state

Status: S1?: Status is uncertain but is somewhere between the following rankings: Inexact rank: ⚘ Critically Imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 5 or fewer occurrences or very few remaining individuals (<1,000) ⚘

Crescent Bugseed: A Rare Colorado Native Worth Protecting

If you’ve never heard of crescent bugseed, you’re not alone. This little-known annual wildflower is one of Colorado’s botanical treasures – and unfortunately, one of its rarest plants. While most native plant enthusiasts are eager to add local species to their gardens, Corispermum navicula presents a unique case that requires special consideration.

What is Crescent Bugseed?

Crescent bugseed is a small annual forb (that’s botanist-speak for a non-woody flowering plant) that belongs to the amaranth family. As an annual, it completes its entire life cycle in just one growing season, sprouting from seed, flowering, producing new seeds, and dying all within the same year. Don’t expect a showy garden star – this modest plant produces tiny, inconspicuous greenish flowers and has narrow leaves that give it a rather understated appearance.

Where Does It Call Home?

Here’s where things get interesting – and concerning. Crescent bugseed is native to the United States, but its range is incredibly restricted. This plant calls only Colorado home, making it what botanists call an endemic species. Even within Colorado, it’s extremely rare, which brings us to an important conservation story.

A Plant in Peril

Crescent bugseed carries a Global Conservation Status of S1?, which translates to critically imperiled. This classification means the plant is extremely rare, with typically five or fewer known populations and fewer than 1,000 individual plants remaining in the wild. That’s a sobering reminder of how fragile our native plant communities can be.

Should You Grow Crescent Bugseed?

This is where we need to pump the brakes a bit. While the instinct of many native plant gardeners is to cultivate rare species as a form of conservation, crescent bugseed requires a more cautious approach. If you’re interested in growing this species, here are the key considerations:

  • Source responsibly: Only obtain seeds or plants from reputable conservation organizations or botanical institutions
  • Don’t collect from the wild: Never harvest seeds or plants from natural populations
  • Consider alternatives: Other native Colorado annuals might better serve your garden goals
  • Support conservation: Consider donating to organizations working to protect rare plant habitats instead

Growing Conditions and Care

If you do source crescent bugseed responsibly, this hardy annual likely prefers the growing conditions typical of Colorado’s native plants. Based on its natural habitat, it probably thrives in:

  • Sandy or well-draining soils
  • Full sun exposure
  • Low to moderate water requirements
  • USDA hardiness zones 4-7 (typical for Colorado)

As an annual, you’ll need to allow the plant to set seed naturally if you want it to return the following year. However, there’s no guarantee of germination success, as many rare plants have specific environmental triggers for seed germination.

Garden Design Role

Honestly? Crescent bugseed isn’t going to be the star of your native plant garden. Its small stature and inconspicuous flowers make it more of a botanical curiosity than a landscape showstopper. If you’re looking for native Colorado annuals that pack more visual punch, consider alternatives like Rocky Mountain beeplant or native sunflowers.

Wildlife and Pollinator Value

The tiny, wind-pollinated flowers of crescent bugseed provide minimal benefits to pollinators compared to more showy native species. Its seeds might provide some food for small birds or rodents, but again, you’d get more wildlife bang for your buck with other native Colorado plants.

The Bottom Line

Crescent bugseed represents something precious in the plant world – a unique species that exists nowhere else on Earth except in Colorado. While it’s tempting to want to grow every native plant we encounter, sometimes the best thing we can do for rare species is to protect their wild habitats and support conservation efforts rather than cultivation.

If you’re passionate about supporting Colorado’s native plant heritage, consider volunteering with local botanical organizations, supporting habitat preservation, or focusing your garden on more common (but equally valuable) native species that can thrive in cultivation while supporting local wildlife.

After all, some plants are meant to remain wild treasures, and crescent bugseed might just be one of them.

Crescent Bugseed

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Caryophyllidae

Order

Caryophyllales

Family

Chenopodiaceae Vent. - Goosefoot family

Genus

Corispermum L. - bugseed

Species

Corispermum navicula Mosyakin - crescent bugseed

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