Hypericum perforatum (Common St. Johnswort)

Plant Info
Also known as: Klamath-weed
Family:Hypericaceae (St. John's-wort)
Life cycle:perennial
  • Invasive - ERADICATE!
Habitat:sun; fields, roadsides, woodland edges, disturbed soil
Bloom season:June - September
Plant height:1 to 3 feet
Wetland Indicator Status:GP: UPL MW: FACU NCNE: UPL
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 Cluster type: flat

[photo of flower]  Flowers are about 1 inch across, 5 yellow petals with tiny black dots around the edges, and numerous long yellow-tipped stamens, which may also be dotted, exploding from the center. Each flower is usually on a short stalk, with many flowers branching off the top part of the plant.

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

[photo of leaves] Leaves are generally oval to oblong, 1 to 2 inches long, about ¼ inch wide, with rounded tips and no leaf stalk, oppositely attached. Most leaves have scattered tiny translucent dots; when held up to the light they give the impression the leaf is perforated (and is where the scientific name comes from). Stems are green, smooth and leafy.

Fruit: Fruit type: capsule/pod

[photo of fruit] Seed pod is a 3-sectioned capsule, about ¼ inch long, that turns deep reddish brown as it matures. Each section has a little “tail” at the top.


The dots on the leaves and petals are actually sacs of essential oils, used as an herbal remedy to treat everything from depression to infection. The black dots on the petals can dye your skin red when they're crushed. Common St. John's-wort can be quite invasive, forming dense colonies and crowding out native plants. Roadside infestations have become a common sight. In Ownbey and Morley's plant atlas Vascular Plants of Minnesota, published in 1991, there were only a dozen records in 8 counties. In 20 years this has jumped to 57 records in 24 counties and I have no doubt it is still an under-reported species. All Hypericum species have switched from the Clusiaceae family to Hypericaceae.

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More photos

Photos by K. Chayka taken at Long Lake Regional Park, Ramsey County. Photos courtesy Peter M. Dziuk taken in Anoka County, and along a highway ramp in St. Paul.


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

Posted by: Mark - Oakdale Nature Preserve, Oakdale MN
on: 2010-06-19 16:53:05

June 2010, in the meadow southwest of the Discovery Center.

Posted by: Sherrie - Apple Valley
on: 2018-08-12 22:25:32

To the moderator: can you point me in the direction of wild St. John's wort? I'm looking to harvest the flowers to make an infused oil. I would be happy to harvest it!

Posted by: K. Chayka
on: 2018-08-13 05:26:29

To Sherrie: the short answer is no. We do not track it to that extent.

Posted by: Jim Cramton - Jones TWP Beltrami County
on: 2019-07-17 12:55:22

I found this plant growing in an opening in the woods near the Pine Point canoe landing on the Mississippi river. This is the first I have seen of it growing in Beltrami county. Plausible seed sources include logging equipment following the 2012 and 2013 July storms, off road traffic, Mississippi river paddlers, and campers.

Posted by: Brenda Ruberto - Saint Michael, Wright County
on: 2019-07-28 07:59:08

Found last year and this year in the wildflower area of our yard.

Posted by: Brett - Lake County
on: 2019-10-02 18:08:22

Think I found a couple of plants on top of Palisade Head.

Posted by: Valiree Green - Houston Co.
on: 2020-07-21 15:09:09

former CRP area now being mowed to be pasture

Posted by: Peter - Afton, MN
on: 2021-02-04 12:18:27

This stuff is EVERYWHERE. We do our best to get rid of it, but there's just too much of it. We're getting a controlled burn done soon, maybe that will help. The bees seem to love it, so maybe it has some use, but the harm outweighs the benefit.

Posted by: Evangeline Moen - north Central, Mille Lacs area
on: 2021-06-21 17:16:51

What is the specific harm of St.John's Wort?

Posted by: K. Chayka
on: 2021-06-21 17:56:36

Evangeline, it degrades the ecosystem and can crowd out native plants that our native pollinators and wildlife need to survive and thrive.

Posted by: Shelby - Minneapolis
on: 2022-06-28 23:45:11

Peter, can you tell me where I might find it growing near you? I'm an herbalist & St. John's Wort is one of my favorite plants to work with. Thank you!

Posted by: K Chayka
on: 2022-06-29 06:30:48

Shelby, this is not an appropriate forum for that type of request. Seek out a forager's group.

Posted by: Jennifer Carlson - Red Wing
on: 2023-06-25 12:42:51

We have it growing in our pasture.

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