shrubN. America Native

Sunny Boulevard St. John's Wort

Hypericum kalmianum 'Piihyp I'

Not currently listed at our partner nurseries.

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Essentials

At a Glance

Plant Type

Shrub

Height

36 inches

Width

36 inches

Light

Full Sun, Partial Sun

Zones

4, 5, 6, 7

Water

Low to moderate

Humidity

Adaptable

Lifespan

Deciduous shrub, 10-20 years

Native To

Great Lakes region, North America

Toxicity

Mildly toxic if ingested

The Story

Plant Bio

Hypericum kalmianum is a small, dense, semi-evergreen shrub native to the Great Lakes region of North America. It is valued for its hardiness, adaptability, and bright yellow summer flowers. Sunny Boulevard ('PIIHYP-I') is a selection noted for its narrow, upright habit, handsome blue-green foliage, and prolific display of sunny yellow flowers. It is also rust-resistant.

Bloom Period:

EarlyLate

Uses & Benefits:

Provides a long season of bright, cheerful yellow flowers throughout the summer. The fine-textured, blue-green foliage offers a nice contrast in the garden even when not in bloom.

This is an extremely tough and adaptable shrub, tolerant of drought, road salt, and a wide range of soils. It's an excellent choice for low-maintenance mass plantings, hedges, or foundation plantings.

The flowers are a valuable source of pollen for a wide variety of native bees and other pollinators. Its dense structure provides cover for small wildlife.

Marketplace

Where to Buy

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Planting

How to Grow

Choose a location with full sun and well-drained soil.
This plant is highly adaptable to different soil types.
Dig a hole as deep and twice as wide as the root ball.
Place the plant in the hole, ensuring the crown is level with the soil.
Backfill with soil, firm it gently, and water well.
Water regularly during the first season to establish.

Pro Tip

This shrub blooms on new wood, so don't hesitate to prune it in early spring to encourage vigorous growth and more flowers.

Keep It Thriving

Care Guide

Do

Provide full sun for best flowering and densest habit.
Prune in early spring to maintain shape and remove dead tips.
Allow the soil to dry out between waterings once established.
Plant in groups for a high-impact display.

Don't

Do not plant in constantly wet or poorly drained soils.
Avoid heavy shade, which will lead to sparse growth and fewer flowers.
Do not over-fertilize; this plant thrives in average to lean soils.
Avoid shearing into a formal shape; allow its natural habit.

Seasonal Care Calendar

Task	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Mulch
Plant
Prune

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Tough and cheerful low hedgeBright accent in perennial bordersDurable plant for massing on slopes

Companion Plants

Echinacea purpurea Perovskia atriplicifolia Panicum virgatum 'Northwind' Sedum 'Autumn Fire' Coreopsis verticillata 'Moonbeam'

Multiply

Propagation Methods

Good to Know

Common Questions

Sunny Boulevard St. John's Wort questions

What zones can Sunny Boulevard St. John's Wort grow in?

Sunny Boulevard 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 St. John's Wort deer resistant?

Yes — Sunny Boulevard 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 St. John's Wort bloom?

Sunny Boulevard 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 Sunny Boulevard St. John's Wort need full sun?

Sunny Boulevard St. John's Wort does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.

Is Sunny Boulevard St. John's Wort drought tolerant?

Yes — once established (usually after the first full season), Sunny Boulevard St. John's Wort handles dry spells with minimal watering. Water deeply its first year to build the root system that makes that possible.