shrubN. America Native

Kalm's St. John's Wort

Hypericum kalmianum

Not currently listed at our partner nurseries.

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Essentials

At a Glance

Plant Type

Shrub

Height

30 inches

Width

30 inches

Light

Full Sun, Partial Sun

Zones

4, 5, 6, 7

Water

Low to moderate

Humidity

Adaptable

Lifespan

10-15 years

Native To

Great Lakes region of North America

Toxicity

Mildly toxic if ingested in large quantities

The Story

Plant Bio

Hypericum is a genus of flowering plants known for their bright yellow, five-petaled flowers with prominent, bushy stamens. Hypericum kalmianum is a compact, dense, mounded shrub native to the Great Lakes region, prized for its blue-green foliage and profuse summer blooms.

Bloom Period:

EarlyLate

Uses & Benefits:

Valued for its long summer bloom period, attractive blue-green foliage, and dense, mounding habit. The exfoliating bark and persistent seed capsules add winter interest.

Excellent for stabilizing slopes and for use in low-maintenance mass plantings or informal hedges where its drought tolerance is a major asset.

The flowers are a significant source of pollen for a wide variety of native bees and other beneficial insects, supporting local pollinator populations.

Marketplace

Where to Buy

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Planting

How to Grow

Select a location with full sun and well-drained soil.
Dig a hole twice as wide as the root ball.
Place the plant in the hole, ensuring the crown is level with the soil.
Backfill with native soil and water thoroughly to settle.
Water regularly during the first season to establish roots.
Apply a light mulch to conserve moisture and suppress weeds.

Pro Tip

Avoid heavy fertilization, which can lead to floppy growth and fewer flowers; this shrub thrives in lean soil.

Keep It Thriving

Care Guide

Do

Provide excellent drainage; it's crucial for plant health.
Prune in late winter or early spring to shape and rejuvenate.
Allow soil to dry out between waterings once established.
Plant in full sun for the best flower production.

Don't

Don't plant in heavy, waterlogged clay soil.
Avoid over-watering, which can cause root rot.
Do not fertilize heavily.
Don't shear into a formal shape; allow its natural mounded form.

Seasonal Care Calendar

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

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Pollinator-friendly border shrubLow-maintenance mass plantingTextural rock garden specimen

Companion Plants

Echinacea purpurea Rudbeckia fulgida Panicum virgatum Sedum 'Autumn Joy' Spiraea japonica

Multiply

Propagation Methods

Good to Know

Common Questions

Kalm's St. John's Wort questions

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

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 Kalm's St. John's Wort deer resistant?

Yes — 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 Kalm's St. John's Wort bloom?

Kalm's 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 Kalm's St. John's Wort need full sun?

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

Is Kalm's St. John's Wort drought tolerant?

Yes — once established (usually after the first full season), 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.