

Upland Brittle Bladderfern Cystopteris tenuis
Upland Brittle Bladderfern is a perennial fern native to Canada and the lower 48 states.
More about this plant
Cystopteris tenuis is sometimes known as Mackay's bladder fern or Mackay's fragile fern. It was long considered to be a part of the superspecies for fragile ferns, as Cystopteris fragilis (L.) Bernh. var. mackayi Lawson. Wikipedia →
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 5 derived from its U.S. range
- Lifespan
- Perennial
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 (10) 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).
Loading…
BibTeX
Loading…