Yellow Screwstem Bartonia virginica
Yellow Screwstem is an annual wildflower native to Canada, the lower 48 states, and Saint-Pierre & Miquelon. It blooms Jul – Oct.
More about this plant
Bartonia virginica, also called yellow screwstem or yellow bartonia, is a species of a flowering plant in Gentianaceae. Native to much of eastern North America, B. virginica grows in wetland habitats, especially bogs, wet meadows, and swales. It is an annual species with small pale green to yellow flowers, scale-like leaves, and reduced, hairless roots. Unlike most other species in the gentian family, B. virginica relies on underground fungal partners for many of its nutrients, a strategy known as partial mycoheterotrophy. While it is rare and threatened in some parts of its range, B. virginica is considered a globally secure species. Wikipedia →
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 5 derived from its U.S. range
- Lifespan
- Annual
- Flower colour
- Green AI AI image-analysis of community-science photos — lower-confidence (a more subjective call, often an inconspicuous flower); not a botanical record
Related plants
More Bartonia →
How we know this (2) Methods & honest limits
We take the plant’s U.S. county range and look up each county’s long-term climate, then summarise: native rainfall = the median annual rainfall across its counties; heat tolerance = the warm end (90th percentile) of average temperature across its range (mirroring how our cold-hardiness floor uses an extreme). Counties + medians blunt the roadside/observer bias that makes point-level climate unreliable. Needs at least five placeable counties.
Honest limits: A realized, sampling-biased niche (where it has been recorded, not its physiological optimum), and county climate is coarse — large Western counties span deserts and mountains. Derived guide, never a measured fact.
McKenzie et al. assigned each species a flower colour with a GPT-4V vision model over iNaturalist photos. We use the confident tier plus a separately-labelled lower-confidence top-up (mostly inconspicuous green/brown flowers), and render it as a small tint — never as an asserted fact, and kept out of the written synopsis.
Honest limits: AI image inference (~87% expert agreement on the confident tier); a decorative, confidence-tiered indicator, not a measured trait.
Sources for this entry (14) Open & cited
Cite this page Open data, please attribute
PlantKey’s data is open under CC BY-SA 4.0 — free to reuse and adapt, with attribution and the same licence. Photos keep their own per-image licence + credit (see Sources above).
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