great St. Johnswort
Hypericum ascyron · Clusiaceae
great St. Johnswort (Hypericum ascyron) is a perennial herbaceous plant in the Clusiaceae family. It is native to North America. USDA records it as hardy in zone 4 and warmer, down to about -23°F.
At a glance
| Type | forb-herb USDA |
|---|---|
| Lifecycle | perennial USDA |
| Native status | native USDA |
| Mature height | 5 ft USDA |
| Light | full-sun USDA |
| Water need | medium USDA |
| Growth rate | moderate USDA |
| Soil pH | 5.7–7.1 USDA |
| Bloom | August–September USDA |
| Flower color | Yellow USDA |
| Hardiness zones | 4 and warmer USDA |
| Guild layer | herb-layer Derived |
| Nursery availability | No Known Source USDA |
USDA quoted from the USDA PLANTS database · Derived computed by a fixed rule from those columns. No value on this page is estimated.
Growing conditions
It needs full sun. USDA rates it as having moderate water needs. Its drought tolerance is rated low. It handles periodically wet ground (USDA rates its anaerobic tolerance medium). It is recorded on soils from pH 5.7 to 7.1 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 4.
Size and growth
At maturity it reaches about 5 ft, making it roughly waist to chest height. It grows at a moderate rate.
Bloom period
USDA records a bloom period of August through September. Flowers are yellow.
A flowering date, not a pollinator rating.
Foliage, flower and season
Summer foliage is green, coarse in texture. Its flowers are conspicuous. Its active growth period is spring and summer. USDA rates its lifespan as long.
What the site needs to provide
USDA records it across sites receiving 32 to 55 inches of annual precipitation. It needs at least 80 frost-free days to finish its season. It roots to at least 14 inches. Fertility requirement: medium.
Propagating it
Propagate it from container stock and sprigs. Seed needs cold stratification — a period of moist chilling — before it will germinate, so sow in autumn or chill it artificially before a spring sowing. Its seed spreads at a slow rate. It does not spread vegetatively, so it will stay where you put it.
Resilience and wildlife
Browsing animals rate it barely palatable — the sourced basis for calling it deer-resistant. Its fire tolerance is rated high. Its growth form is recorded as single crown.
Role in a guild
Herb layer. In a layered planting this is the herbaceous middle — perennials and grasses that fill the space between ground cover and shrubs. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Others in Hypericum
- tinker's penny Hypericum anagalloides
- northern St. Johnswort Hypericum boreale
- Aaron's beard Hypericum calycinum
- roundpod St. Johnswort Hypericum cistifolium
Similar role and hardiness
- common oat Avena sativa
- Caucasian bluestem Bothriochloa bladhii
- black grama Bouteloua eriopoda
- cosmopolitan bulrush Bolboschoenus maritimus
- Carolina fanwort Cabomba caroliniana
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol HYAS80, or is computed from those values by a fixed rule. Nothing here is estimated or model-generated. Where USDA publishes no value, this page omits the claim rather than filling the gap.
- Quoted from USDA PLANTS: active growth period, Bloom, Bloom end, browse palatability, cold stratification, Drought tolerance, fall conspicuous, fertility requirement, fire tolerance, Flower color, flower conspicuous, foliage color, foliage porosity winter, foliage texture, frost free days min, fruit conspicuous, growth form, Growth rate, Hardiness zones, Lifecycle, lifespan, Light, Mature height, Minimum temperature, Native status, Nitrogen fixation, Nursery availability, precipitation max in, precipitation min in, propagation, resprout ability, root depth in, seed spread rate, Soil pH, Soil pH (upper), Tolerance of wet soil, Toxicity, Type, vegetative spread rate, Water need.
- Derived by a fixed rule from those columns: Guild layer.
Read our full data sources and methodology.
Find more plants for your zone with the Plant Finder.