Black-eyed Susan Rudbeckia hirta
A cheerful, fast-establishing golden daisy — often grown as a short-lived perennial or biennial. Reliable nectar for bees and small butterflies all summer.
Growing & care
USDA PLANTS · TRY- Sun
- Full sun
- Soil & moisture
- Dry – medium
- Soil pH
- 6–7
- Fertility need
- Medium
- Adapts to
- Medium (loam), Fine (clay)
- Hardiness
- USDA zone 3 – 9
- Height
- 1 – 3 ft
- Mature width
- ~ 1 ft wide DERIVED derived estimate — open-grown crown allometry (height × growth-form ratio); not a measurement
- Spread
- None — clumping
- Growth rate
- Rapid
- Growth form
- Single stem
- Lifespan
- Annual · short-lived
- Foliage
- Broadleaf · coarse texture
- Active growth
- Autumn through spring
- Fruit
- Brown
- Flower colour
- Yellow 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
- Deer browsing
- Low often deer-resistant
- Resprouts if cut
- No
Sow timing keys off your local last- and first-frost dates.
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~16 caterpillar species
Rudbeckia supports ~16 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 moderate genus.
Recorded feeding on Rudbeckia in North America, including:
+ 8 more species → ↑ show fewer
✦ Bees specialist-bee host · 104 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. Rudbeckia is a recorded specialist-bee host, so losing it can mean losing the bee that relies on it.
104 native & managed bee species are documented visiting Black-eyed Susan — the 12 most-recorded:
Wildlife & visitors 120 nectaring
Open records of who else uses Black-eyed Susan — a generalist food-web signal, kept separate from the keystone Ecological Value.
120 adult butterfly & moth species are recorded nectaring at its flowers — the most-recorded:
Across 31 U.S. vegetation-survey plots that recorded Black-eyed Susan, these catalog species turned up most often in the same plot — a real field co-occurrence signal, not a planting prescription.
Related plants
More Rudbeckia →
How we know this (5) Methods & honest limits
We read each species’ measured specific leaf area (leaf area per unit dry weight) from the Global Spectrum dataset and band it: thin & fast (high SLA), medium, or thick & tough (low SLA). The global median is about 10 mm²/mg.
Honest limits: A species-mean from pooled measurements — individual plants vary with light and site. A broad strategy signal, not a precise per-plant figure.
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.
For woody plants that have a height but no measured crown, we estimate width = height × a crown-to-height ratio fit for that plant’s form (conifers narrower than broadleaf trees, shrubs widest), calibrated on our measured open-grown crowns and capped at the largest one ever measured. A measured crown always wins; herbaceous plants get nothing (no anchor).
Honest limits: A coarse class-median estimate for garden-scale spacing, not a measurement; woody single/multi-stem forms only.
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 (38) 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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