Hypericum ascyron (Great St. Johnswort)

Plant Info
Also known as: Giant St. John's-wort
Family:Hypericaceae (St. John's-wort)
Life cycle:perennial
Habitat:sun; moist; along shores, wet meadows, thickets
Bloom season:July - August
Plant height:2 to 5 feet
Wetland Indicator Status:GP: none MW: FAC NCNE: FAC
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 5-petals

[photo of flowers] Flowers are from 2 to 2½ inches across with 5 bright to golden yellow petals and many long yellow stamens with orange tips. In the center is a green pyramid shaped ovary with 4 or 5 red-tipped styles that are fused at the base. A flowers is at the end of a stem that arises from a leaf axil in the upper part of the plant.

Leaves and stem: Leaf attachment: opposite Leaf type: simple

[photo of leaves] Leaves are up to 3 inches long and 1 inch wide, toothless and hairless, rounded at the base and slightly tapering to a point at the tip, with no leaf stem. There are glandular dots or streaks scattered on the surface. Attachment is opposite. The main stem is 4-angled on young plants, becoming 4-lined with maturity.

Fruit: Fruit type: capsule/pod

[photo of fruit] Fruit is a pyramid-shaped capsule with 5 chambers, about 1 inch long. It dries to brownish black and opens at the top when the seed is ripe.

[photo of seed] Seed is cylindrical, dark brown, about 1 millimeter long, and resembles a tiny ear of corn.


While the general shape of this flower resembles other St. John's-wort species, the size of the flower sets Great St. John's-wort apart from the rest. According to Flora of North America, there are at least 3 subspecies of Hypericum ascyron, but apparently only subsp. pyramidatum is present in North America. Formerly known as Hypericum pyramidatum, it is part of a variable species or species complex with a wide distribution throughout the northern hemisphere.

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More photos

Photos by K. Chayka taken at Wild River State Park, Chisago County. Photos courtesy Peter M. Dziuk taken in a private garden in Anoka County (it did not persist well there)


Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: James - Benton County
on: 2010-07-11 15:45:45

I think I have the ID correct.

Posted by: Kristy - Redwood County, Sherman Twp
on: 2011-07-14 13:58:55

Found today, 7/14/2011, in a remnant rock out-crop prairie. A small area, probably 15-20 plants on high ground. First time sighting.

Posted by: Brett - Otsego
on: 2014-07-28 22:01:14

Saw a few of these plants down along the river bottom in Clear Lake SNA. Too many invasives here though.

Posted by: Connie - SW mpls
on: 2015-11-13 13:40:58

I asked the master gardners what I have in my back yard. It's so tall I wasn't sure if it is st johns wort, but they think it is, after looking at my pics.I think I'll collect some seeds for next year, if it's not too late. Just letting you know. Connie

Posted by: K. Chayka
on: 2015-11-13 19:07:56

We have some Hypericum pyramidatum in our yard. We love it, but it is actually becoming a little bit of a nuisance in the vegetable garden. :-)

Posted by: Darlene - Mille Lacs County, Page Township
on: 2016-07-03 09:16:47

There's about eight plants just about ready to open and blossom. The path goes through a wooded, swampy area and then to a almost field like situation where they made their home.

Posted by: Tim Johnson - Coon Rapids Dam, Hennepin county
on: 2018-07-05 10:22:49

This wildflower is just starting to bloom in the grassy areas of the flood plain along the Mississippi River.

Posted by: Myron Huntley - Isle
on: 2018-07-10 11:23:12

Noticed this plant this morning July 10 2018

Posted by: Regan Golden - St. Paul
on: 2018-07-24 14:24:12

I purchased this plant in St. Paul and the first year it was pretty tame, but this summer it is enormous and the bees are just crazy about the flowers. What an amazing plant!

Posted by: Linda Thomas - Olmsted county
on: 2018-07-25 20:40:07

It is Great St Johnswort

Posted by: Kenny h - Shooting Star Trail
on: 2019-07-08 05:32:23

Found the Great St. John's wort for the first time today...old railroad prairie remnant...the flower head size and pyramid center was the easiest way to ID for me...also received ID from one of my 167K member plant ID groups.

Posted by: Kathy Rice - Lebanon Hills Regional Park Eagan MN
on: 2019-07-14 09:26:50

Several plants east of the pond near the equestrian trailhead

Posted by: Krista Botsford - wausau, wisconsin
on: 2019-07-21 17:30:49

I just found it growing in my field, next to my 25 year old prairie!!!

Posted by: Dale Ogren - near Mirror Lake in Itasca County
on: 2020-06-30 16:33:42

Great St. John's wort used to grow in a few sunny spots in the Boy Scout camp on Mirror Lake. It has been absent the past few summers, and I suspect mowing was the cause of its disappearance. Does anybody know where I could get seeds to start some at my cabin on Mirror Lake?

Posted by: Bruce Baer - Dakota County
on: 2021-07-10 12:49:36

West end of the Lebanon Hills County Park Jensen Lake unit. This on July 10th.

Posted by: D Duran - Miesville Ravine Park Reserve Dakota County
on: 2021-07-17 14:05:17

My first time noticing these; thought they were jumbo buttercups at first. The bumblebees were going nuts over them.

Posted by: Jodi Hilderbrand - Lanesboro
on: 2023-07-13 15:50:40

At first I saw just one very tall yellow wildflower cluster poking up among a field of purple beebalm. But when I looked around more carefully, I found quite a few of these Great St. John's-wort plants blooming. This is the first time I've seen these flowers in our meadow.

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