When does Great St. Johnswort bloom?

Great St. Johnswort typically flowers from June through August, producing bright yellow, star shaped blooms on tall upright stems.

What kind of light does Great St. Johnswort need?

It grows best in full sun but can tolerate part sun to part shade, especially where soil moisture stays consistent through the growing season.

How much water does Great St. Johnswort require?

This plant prefers medium to consistently moist soil and does well near wet meadows, ditches, streambanks and other seasonally saturated sites.

What pollinators visit Great St. Johnswort flowers?

Bees, butterflies and beetles regularly visit the flowers for pollen, since Hypericum species do not produce nectar.

What growth habit does Great St. Johnswort have?

It is a herbaceous forb that dies back to the ground each year, sending up new upright stems in spring.

Is Great St. Johnswort toxic to livestock?

The USDA PLANTS Database does not flag Great St. Johnswort as toxic to livestock.

Is Great St. Johnswort HOA-friendly?

Great St. Johnswort is generally an HOA-friendly choice in the right placement, with low maintenance.

Great St. Johnswort

Name: Pollinator Patch
Author: Pollinator Patch

Hypericum ascyron

Last reviewed: September 2026

Great St. Johnswort is an upright forb that blooms with bright yellow flowers from June through August in wet meadows, stream banks and marsh edges across the northeastern and midwestern United States.

Toxicity unknown

Great St. Johnswort (Hypericum ascyron) is not listed by the ASPCA Animal Poison Control Center (opens in new tab) or the other sources we check, so we have no verdict for it either way. Absence from those lists is not a clearance. If your pet shows symptoms after eating any plant, call the ASPCA at (888) 426-4435.

The USDA PLANTS Database (opens in new tab) does not flag Great St. Johnswort as toxic to livestock.

Light

full sun

Water

medium

Size

24"–48" H × 12"–24" W

Bloom

Jun, Jul, Aug

Native to

CT, IA, IL, IN and 13 more states

Pollinators

bees, butterflies, beetles

Before you buy

Your city may pay you to plant this

Cities and water utilities offer rebates for replacing lawn with native and water-wise plants. We track 452 programs across 44 states, each with a link to the provider and the date we last checked it.

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Browse plants for this ecoregion

Western Corn Belt Plains Northern Lakes and Forests North Central Hardwood Forests Driftless Area Southeastern Wisconsin Till Plains Eastern Corn Belt Plains Southern Michigan/Northern Indiana Drift Plains Northeastern Highlands Northeastern Coastal Zone Northern Allegheny Plateau Erie Drift Plain Northern Forests Northern Piedmont Ridge and Valley Western Allegheny Plateau Eastern Great Lakes Lowlands

Great St. Johnswort is a tall native perennial that produces bright yellow flowers with prominent stamens from June through August. This robust plant forms upright clumps and thrives in full sun with moderate water needs.

Growing Great St. Johnswort

Grow Great St. Johnswort in full sun and medium water. Mature plants reach 24 to 48 inches tall and spread 12 to 24 inches wide. Expect low maintenance to keep it looking intentional in a front yard.

In an HOA neighborhood

Great St. Johnswort is an HOA-friendly choice. Maintenance level: low. Tidiness: 3 out of 5.

Works well in: mid zone, foundation.

Tall height may appear unstructured in formal settings
Winter dormancy leaves bare stems

Wildlife value

The cheerful yellow blooms attract bees, butterflies, and beetles throughout the summer months. This native plant provides important nectar resources during peak growing season.

Common questions

When does Great St. Johnswort bloom?: Great St. Johnswort typically flowers from June through August, producing bright yellow, star shaped blooms on tall upright stems.
What kind of light does Great St. Johnswort need?: It grows best in full sun but can tolerate part sun to part shade, especially where soil moisture stays consistent through the growing season.
How much water does Great St. Johnswort require?: This plant prefers medium to consistently moist soil and does well near wet meadows, ditches, streambanks and other seasonally saturated sites.
What pollinators visit Great St. Johnswort flowers?: Bees, butterflies and beetles regularly visit the flowers for pollen, since Hypericum species do not produce nectar.
What growth habit does Great St. Johnswort have?: It is a herbaceous forb that dies back to the ground each year, sending up new upright stems in spring.
Is Great St. Johnswort toxic to livestock?: The USDA PLANTS Database does not flag Great St. Johnswort as toxic to livestock.
Is Great St. Johnswort HOA-friendly?: Great St. Johnswort is generally an HOA-friendly choice in the right placement, with low maintenance.

These answers were drafted with an AI model from this plant's data. Verify care details with a local expert.

Native range data from vouchered herbarium specimen records and regional native plant society lists. Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.

If something looks wrong

Common plant problems, and what to check first

These come up on almost any plant. Each guide lists the likely causes in the order they are worth ruling out, with one thing to check before you act on any of them, and links to the source it came from.

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Ready to grow Great St. Johnswort? Add it to your garden in Pollinator Patch to track it and get season-by-season care guidance.

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