Hypericum pyramidatum (Great St. Johnswort)

Plant Info
Also known as: Giant St. John's-wort
Genus:Hypericum
Family:Hypericaceae (St. John's-wort)
Life cycle:perennial
Origin:native
Habitat:sun; moist; along shores, wet meadows, thickets
Bloom season:July - August
Plant height:2 to 5 feet
Wetland Indicator Status:none
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.

Notes:

While the general shape of this flower resembles other St. John's-wort species, the size of the flower sets it apart from the rest. Great St. John's-wort also goes by Latin name Hypericum ascyron, but the accepted name in Minnesota is Hypericum pyramidatum. All Hypericum species have switched from the Clusiaceae family to Hypericaceae.

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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)

Comments

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.

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