North America Non-native Plant

Twoflower Rattlebox

Botanical name: Crotalaria biflora

USDA symbol: CRBI8

Life cycle: annual

Habit: forb

Native status: Non-native, reproduces and persists in the wild in the lower 48 states  

Twoflower Rattlebox: A Non-Native Wildflower You Might Spot in Virginia If you’ve been exploring Virginia’s wild spaces and noticed small yellow flowers blooming in pairs on slender stems, you might have encountered the twoflower rattlebox (Crotalaria biflora). This annual forb has quietly made itself at home in the Old Dominion ...

Twoflower Rattlebox: A Non-Native Wildflower You Might Spot in Virginia

If you’ve been exploring Virginia’s wild spaces and noticed small yellow flowers blooming in pairs on slender stems, you might have encountered the twoflower rattlebox (Crotalaria biflora). This annual forb has quietly made itself at home in the Old Dominion State, though it’s not originally from around these parts.

What Is Twoflower Rattlebox?

Twoflower rattlebox is a non-native herbaceous plant that belongs to the pea family. As its common name suggests, this plant typically produces its small yellow flowers in pairs – a characteristic that makes it relatively easy to identify. Like other members of the Crotalaria genus, it gets the rattlebox part of its name from the way its dried seed pods rattle when shaken.

This annual forb lacks woody stems and dies back completely each year, starting fresh from seed the following growing season. It’s what botanists call a forb – essentially a flowering plant that isn’t a grass, sedge, or woody shrub.

Where You’ll Find It

Currently, twoflower rattlebox has been documented growing wild in Virginia, where it reproduces on its own without human intervention. This introduced species has managed to establish itself and persist in the landscape, though its distribution appears to be limited compared to more widespread non-native plants.

Should You Grow Twoflower Rattlebox in Your Garden?

Here’s where things get interesting – while twoflower rattlebox isn’t considered invasive or particularly harmful, it’s also not exactly what you’d call a garden showstopper. This plant is more of a curiosity than a cultivated ornamental, and most gardeners encounter it as a volunteer rather than something they’ve intentionally planted.

Garden Value and Appearance

If you’re looking for aesthetic appeal, twoflower rattlebox offers modest charm at best. The small yellow flowers are pleasant enough, but they’re not particularly showy or long-lasting. The plant tends to have a somewhat weedy appearance, which might not fit well with more formal garden designs.

That said, if you appreciate the subtle beauty of wildflowers and enjoy observing how non-native species adapt to local conditions, you might find twoflower rattlebox mildly interesting. The paired flowers are actually quite charming up close, and the rattling seed pods add a fun tactile element.

Growing Conditions

Like many members of the pea family, twoflower rattlebox isn’t particularly fussy about growing conditions. It can tolerate poor soils and sunny locations, making it a hardy survivor in challenging environments. However, since specific care information for this species is limited, and it’s not commonly cultivated, detailed growing guides are scarce.

Better Native Alternatives

If you’re drawn to the idea of small yellow wildflowers in your garden, consider these beautiful native Virginia alternatives instead:

  • Wild senna (Senna hebecarpa) – Also in the pea family with bright yellow flowers
  • Partridge pea (Chamaecrista fasciculata) – Delicate yellow blooms and interesting seed pods
  • Wild indigo species (Amorpha species) – Native legumes that support local ecosystems
  • Goldenrod varieties (Solidago species) – Spectacular fall-blooming natives

Supporting Local Ecosystems

While twoflower rattlebox may provide some minor benefits to pollinators, native plants are almost always better choices for supporting local wildlife. Native species have co-evolved with local insects, birds, and other wildlife, creating intricate relationships that non-native plants simply can’t replicate.

When you choose native alternatives, you’re not just creating a beautiful garden – you’re supporting the complex web of life that makes Virginia’s ecosystems so special.

The Bottom Line

Twoflower rattlebox represents an interesting example of how plants adapt and spread beyond their original homes. While it’s not harmful enough to actively remove from wild areas, it’s also not compelling enough to recommend for intentional cultivation. If you encounter it in your travels, appreciate it for what it is – a modest immigrant species making its way in a new land.

For your garden, though, there are so many spectacular native options that will provide better beauty, stronger ecological benefits, and deeper connections to Virginia’s natural heritage. Why settle for ordinary when you can grow extraordinary native plants that truly belong?

Twoflower Rattlebox

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

Fabales

Family

Fabaceae Lindl. - Pea family

Genus

Crotalaria L. - rattlebox

Species

Crotalaria biflora L. - twoflower rattlebox

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