Bushy St. Johnswort Hypericum densiflorum
Bushy St. Johnswort is a perennial shrub native to the lower 48 states. It grows to 6.6 ft and blooms May in full sun, with brown fruit.
More about this plant
Hypericum densiflorum, also known as bushy St. John's wort or dense St. John's wort, is a perennial herb in the flowering plant family Hypericaceae native to North America. The specific epithet densiflorum is Latin, meaning "densely flowered", referring to the many-flowered cymes. Wikipedia →
Growing & care
USDA PLANTS · TRY- Sun
- Full sun
- Soil & moisture
- Medium moisture
- Soil pH
- 4–7.5
- Fertility need
- Low
- Adapts to
- Coarse (sandy), Medium (loam), Fine (clay)
- Hardiness
- USDA zone 8+
- Height
- 6.6 ft
- Mature width
- ~ 6 ft wide DERIVED derived estimate — open-grown crown allometry (height × growth-form ratio); not a measurement
- Spacing
- 4–5 ft apart from USDA planting density
- Spread
- None — clumping
- Growth rate
- Slow
- Growth form
- Multiple stems
- Lifespan
- Perennial · moderate
- Foliage
- Broadleaf · fine texture
- Active growth
- Spring
- Fruit
- Brown persists into winter
- Flower colour
- Yellow AI AI image-analysis of community-science photos (~87% expert agreement) — not a botanical record
- Propagate by
- Bare root, Container
- Seed starting
- No stratification needed
- Seeds ripen
- Spring – Summer seed-collection / harvest window
- In the trade
- Routinely available
- Deer browsing
- Low often deer-resistant
- Resprouts if cut
- Yes regrows after top-kill
Sow timing keys off your local last- and first-frost dates.
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~20 caterpillar species
Hypericum supports ~20 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 Hypericum in North America, including:
+ 8 more species → ↑ show fewer
✦ Bees 1 bee visitor
1 native & managed bee species is documented visiting Bushy St. Johnswort :
Related plants
More Hypericum →
How we know this (3) 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.
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 (32) 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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