Great St. John's Wort
Hypericum ascyron
Essentials
At a Glance
Plant Type
Shrub
Height
48 inches
Width
24 inches
Light
Full Sun, Partial Sun
Zones
4, 5, 6, 7, 8
Water
Moderate, prefers moist soils
Humidity
Average garden humidity
Lifespan
Perennial
Native To
North America
Toxicity
Toxic if ingested
The Story
Plant Bio
Hypericum ascyron, commonly known as great St. John's wort, is a deciduous shrub recognized for its upright growth, lush green foliage, and clusters of bright yellow flowers that often have prominent stamens. This species is appreciated for its large, showy flowers and its ability to attract pollinators, making it a popular choice for ornamental gardens and naturalized landscapes.
Bloom Period:
Uses & Benefits:
Marketplace
Where to Buy
Shipping costs Year-round shipping Free shipping
Planting
How to Grow
- Tuck seeds or cuttings into well-draining soil in spring.
- Water regularly until established, about 6 weeks.
- Choose a sunny spot for optimal flowering.
- Apply a balanced fertilizer in early spring.
- Prune lightly after flowering to maintain shape.
- Mulch around base to retain moisture.
Pro Tip
Prefers moist, well-drained soils; avoid drought conditions during establishment.
Keep It Thriving
Care Guide
Do
- Water regularly during dry spells 🌱
- Prune after flowering to promote bushiness
- Fertilize annually with a balanced fertilizer
- Mulch to conserve moisture
Don't
- Overwater to prevent root rot ❌
- Ignore pruning after flowering
- Use high-nitrogen fertilizer in fall ❌
Seasonal Care Calendar
| Task | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Divide | ||||||||||||
| Prune |
Watch Out For
Pests & Diseases
Common Pests
Common Diseases
In the Garden
Landscape Uses & Companions
Landscape Uses
Companion Plants
Multiply
Propagation Methods
Good to Know
Common Questions
Great St. John's Wort questions
What zones can Great St. John's Wort grow in?
Great St. John's Wort is hardy in USDA Zones 4–8. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.
Is Great St. John's Wort deer resistant?
Yes — Great St. John's Wort is rated deer-resistant. Deer typically pass it over, though extreme hunger can override any plant's defenses.
When does Great St. John's Wort bloom?
Great St. John's Wort typically blooms in mid-summer through late summer. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.
Does Great St. John's Wort need full sun?
Great St. John's Wort does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.
More Hypericum to compare
Hypericum frondosum Goldmound
Hypericum frondosum
Variegated Hypericum
Hypericum patulum 'Hidcote Variegated'
Shrubby St. Johnswort
Hypericum prolificum
Kalm's St. John's Wort
Hypericum perforatum 'Sunny Boulevard'
Kalm's St. John's Wort
Hypericum kalmianum
Gemo St. Johnswort
Hypericum kalmianum 'Gemo'
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See it in a design of your actual yard, get zone-matched care reminders, and track it season by season in your garden journal.
