

Palmer's Grapplinghook Harpagonella palmeri
Palmer's Grapplinghook is an annual wildflower native to the lower 48 states. It blooms Mar – May.
More about this plant
Harpagonella is a genus of flowering plants in the borage family. They are known as the grappling-hooks, because of the appearance and function of their fruits. The strange fruits are two small nutlets enclosed in a burlike calyx, which is armed with numerous spines covered in minute, hooked barbs. These diminutive, annual plants are found in sandy, clayey, and gravelly soils, and have small white flowers. This genus is native to North America, and is found in southern California, southern Arizona, northern Sonora, and the Baja California peninsula. Wikipedia →
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 10 derived from its U.S. range
- Lifespan
- Annual
How we know this (1) 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.
Sources for this entry (12) Open & cited
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