North America Native Plant

Hayfield Tarweed

Botanical name: Hemizonia congesta calyculata

USDA symbol: HECOC5

Life cycle: annual

Habit: forb

Native status: Native to the lower 48 states  

Synonyms: Hemizonia calyculata (Babc. & H.M. Hall) D.D. Keck (HECA6)   

Hayfield Tarweed: A California Native Worth Knowing If you’re looking to add authentic California character to your wild garden or restoration project, meet hayfield tarweed (Hemizonia congesta calyculata). This unassuming annual might not win any beauty contests, but it’s got charm in spades and plays an important role in California’s ...

Rare plant alert!

Region: Conservation status by state

Status: S5T3: Status is uncertain but is somewhere between the following rankings: Subspecies or variety is 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. ⚘ Secure: At very low or no risk of extinction in the jurisdiction due to a very extensive range, abundant populations or occurrences, with little to no concern from declines or threats. ⚘

Hayfield Tarweed: A California Native Worth Knowing

If you’re looking to add authentic California character to your wild garden or restoration project, meet hayfield tarweed (Hemizonia congesta calyculata). This unassuming annual might not win any beauty contests, but it’s got charm in spades and plays an important role in California’s native plant communities.

What Is Hayfield Tarweed?

Hayfield tarweed is a native California annual forb – basically, that means it’s a soft-stemmed plant (not woody) that completes its entire life cycle in one year. You might also see it listed under its scientific synonym, Hemizonia calyculata. As a member of the sunflower family, it produces small yellow composite flowers that are perfectly suited to California’s Mediterranean climate.

Where Does It Grow?

This California native is found exclusively in the Golden State, where it thrives in grasslands, agricultural fields, and disturbed areas. True to its common name, you’ll often spot it growing in hayfields and similar open spaces throughout the state.

Should You Grow Hayfield Tarweed?

Here’s the honest truth: hayfield tarweed isn’t for every garden. This is definitely a plant for gardeners who appreciate the subtle beauty of California’s native grasslands and want to support local ecosystems. If you’re creating a formal garden or looking for showy flowers, you might want to look elsewhere.

Reasons to grow it:

  • It’s authentically Californian – supporting true native biodiversity
  • Requires minimal water once established
  • Attracts native bees and other small pollinators
  • Perfect for naturalized areas and restoration projects
  • Thrives in poor soils where other plants struggle

Reasons you might skip it:

  • Not particularly ornamental or eye-catching
  • Annual nature means it needs replanting each year
  • Better suited for wild gardens than formal landscapes
  • Can be weedy in appearance

Growing Hayfield Tarweed Successfully

If you’ve decided this California native fits your gardening goals, you’re in luck – it’s relatively easy to grow once you understand its needs.

Growing Conditions:

  • Full sun exposure
  • Well-draining, even poor soils
  • Minimal summer water once established
  • Thrives in USDA zones 8-10

Planting and Care Tips:

  • Direct seed in fall when rains begin
  • Scatter seeds on prepared soil surface – no need to bury deeply
  • Water lightly until germination occurs
  • Once established, reduce watering significantly
  • Allow plants to go to seed for natural reseeding

The Bottom Line

Hayfield tarweed might not be the star of your garden show, but it’s a valuable supporting player in California’s native plant community. If you’re creating a wild garden, working on habitat restoration, or simply want to support native pollinators with authentic California flora, this humble annual deserves consideration. Just remember – it’s all about setting the right expectations and choosing the right spot in your landscape.

For gardeners seeking more ornamental California natives, consider pairing hayfield tarweed with showier species like California poppies or lupines in your wildflower mix. Sometimes the best gardens are the ones that celebrate both the bold and the subtle characters of our native plant communities.

Hayfield Tarweed

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Asteridae

Order

Asterales

Family

Asteraceae Bercht. & J. Presl - Aster family

Genus

Hemizonia DC. - tarweed

Species

Hemizonia congesta DC. - hayfield tarweed

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