Tanseyleaf Tansyaster Machaeranthera tanacetifolia
Tanseyleaf Tansyaster is an annual wildflower native to Canada and the lower 48 states. It grows to 2 ft and blooms May in part shade – shade, with brown fruit. A host for pollen-specialist native bees.
Growing & care
USDA PLANTS · TRY- Sun
- Part shade – shade
- Soil & moisture
- Medium moisture
- Soil pH
- 6.5–8.5
- Fertility need
- Low
- Adapts to
- Medium (loam)
- Hardiness
- USDA zone 4+
- Height
- 2 ft
- Spread
- None — clumping
- Growth rate
- Rapid
- Growth form
- Single crown
- Lifespan
- Annual
- Foliage
- Broadleaf · medium texture
- Active growth
- Spring & summer
- Fruit
- Brown
- Flower colour
- Purple AI AI image-analysis of community-science photos (~87% expert agreement) — not a botanical record
- Propagate by
- Seed
- Seed starting
- No stratification needed
- Seeds ripen
- Summer seed-collection / harvest window
- In the trade
- Routinely available
- Resprouts if cut
- No
Sow timing keys off your local last- and first-frost dates.
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~6 caterpillar species
Machaeranthera supports ~6 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 Machaeranthera in North America, including:
+ 8 more species → ↑ show fewer
✦ Bees specialist-bee host · 32 bee visitors
Specialist native bees depend on it.
Some native bees are pollen specialists (oligolectic) — they raise young only on pollen from particular plant genera. Machaeranthera is a recorded specialist-bee host, so losing it can mean losing the bee that relies on it.
32 native & managed bee species are documented visiting Tanseyleaf Tansyaster — the 12 most-recorded:
Wildlife & visitors 15 nectaring
Open records of who else uses Tanseyleaf Tansyaster — a generalist food-web signal, kept separate from the keystone Ecological Value.
15 adult butterfly & moth species are recorded nectaring at its flowers — the most-recorded:
Related plants
More Machaeranthera →
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 (31) 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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