Coulter's Spiderling Boerhavia coulteri
Coulter's Spiderling is a plant native to the lower 48 states. It blooms Aug – Oct.
More about this plant
Boerhavia coulteri is a species of flowering plant in the four o'clock family known by the common name Coulter's spiderling. It is native to the southwestern United States and northern Mexico, particularly the desert areas. This is an annual herb producing an erect or creeping stem up to about 70 or 80 centimeters in maximum length. They are slightly hairy and have sticky resin glands toward the bases. The leaves are lance-shaped to somewhat triangular, pointed, sometimes wavy or rippled along the edges, and 5 centimeters in maximum length. Most of the leaves grow from the lower half of the plant. The sticky inflorescence is a small cluster of tiny white to pale pink flowers, each under two millimeters long. The fruit is an elliptical body a few millimeters in length with longitudinal ribs. The fruits are borne in small clusters. Wikipedia →
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 8 derived from its U.S. range
- Flower colour
- Purple AI AI image-analysis of community-science photos (~87% expert agreement) — not a botanical record
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~1 caterpillar species
Boerhavia supports ~1 caterpillar species.
Native butterfly & moth caterpillars are the base of the terrestrial food web — most songbirds rear their young almost entirely on them. As a host for native Lepidoptera this is a modest genus.
Recorded feeding on Boerhavia in North America, including:
Related plants
More Boerhavia →
How we know this (3) Methods & honest limits
A recorded categorical fact: each species is tagged C3 (standard), C4 (heat/water-efficient) or CAM (succulent, night-time CO₂ uptake) — or a facultative combination. We only show a trait card for the noteworthy C4/CAM cases; C3 is the unremarkable majority, kept in the data but not surfaced as a card.
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 (17) 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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