The Story
Plant Bio
Hypericum kalmianum, known as Kalm's St. John's Wort, is a compact, dense, mounded shrub native to the Great Lakes region. It features narrow, blue-green leaves and clusters of bright yellow, five-petaled flowers with prominent stamens in summer.
'Sunny Boulevard' is a particularly hardy and adaptable cultivar, selected for its tight, dense habit, prolific summer-long bloom of sunny yellow flowers, and attractive blue-green foliage. It is rust-resistant and requires little maintenance.
Uses & Benefits:
Essentials
At a Glance
Plant Type
Perennial
Height
30 inches
Width
30 inches
Light
Full Sun, Partial Sun
Zones
4, 5, 6, 7
Water
Low to Moderate
Humidity
Average
Lifespan
Perennial Shrub
Native To
North America (Great Lakes region)
Toxicity
Toxic to livestock; can cause photosensitivity.
Bloom period
Summer – Late summer
In flower about 2 months of the year
Marketplace
Where to Buy
Shipping costs Year-round shipping Free shipping
Planting
How to Grow
- Tuck seeds into well-draining soil in early spring
- Water regularly to keep soil moist but not waterlogged
- Mist cuttings to encourage rooting in warm, bright spot
- Divide mature plants every 3–4 years in early spring
- Mulch around the base to retain moisture during summer
- Transplant in early spring or fall for best results
Pro Tip
Ensure well-draining soil and full sun for optimal growth
Keep It Thriving
Care Guide
Do
- Water during dry spells 🌱
- Prune lightly after flowering
- Apply balanced fertilizer in spring
- Divide every 3–4 years
Don't
- Overwater in winter ❌
- Allow soil to become waterlogged ❌
- Neglect pruning after bloom ❌
- Use chemical pesticides unnecessarily ❌
Seasonal Care Calendar
| Task | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Fertilize | ||||||||||||
| Mulch | ||||||||||||
| Propagate | ||||||||||||
| Prune | ||||||||||||
| Spring Cleanup |
Watch Out For
Pests & Diseases
Common Pests
Common Diseases
In the Garden
Landscape Uses & Companions
Landscape Uses
Multiply
Propagation Methods
Good to Know
Common Questions
Sunny Boulevard Kalm's St. John's Wort questions
What zones can Sunny Boulevard Kalm's St. John's Wort grow in?
Sunny Boulevard Kalm's St. John's Wort is hardy in USDA Zones 4–7. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.
Is Sunny Boulevard Kalm's St. John's Wort deer resistant?
Yes — Sunny Boulevard Kalm's St. John's Wort is rated deer-resistant. Deer typically pass it over, though extreme hunger can override any plant's defenses.
When does Sunny Boulevard Kalm's St. John's Wort bloom?
Sunny Boulevard Kalm's St. John's Wort typically blooms in summer through late summer. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.
Does Sunny Boulevard Kalm's St. John's Wort need full sun?
Sunny Boulevard Kalm's St. John's Wort does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.
Is Sunny Boulevard Kalm's St. John's Wort drought tolerant?
Yes — once established (usually after the first full season), Sunny Boulevard Kalm's St. John's Wort handles dry spells with minimal watering. Water deeply its first year to build the root system that makes that possible.
More Hypericum to compare
Great St. John's Wort
Hypericum ascyron
Hypericum frondosum Goldmound
Hypericum frondosum
Variegated Hypericum
Hypericum patulum 'Hidcote Variegated'
Shrubby St. Johnswort
Hypericum prolificum
Gemo St. Johnswort
Hypericum kalmianum 'Gemo'
Kalm's St. John's Wort
Hypericum kalmianum
Keep exploring
Explore the genus
Hardy in your zone?
Grow Sunny Boulevard Kalm's St. John's Wort with confidence
See it in a design of your actual yard, get zone-matched care reminders, and track it season by season in your garden journal.