Wednesday, June 15, 2011

Weedy Wednesday: St. John's Wort

St. John's Wort is our "Weedy Wednesday" plant this week.  This plant has a conflicted reputation, a devil in one sense because it is a noxious weed, but in another sense a useful herb. It has brought some conflict among gardeners as to whether we should allow it to take root in our gardens too so I thought I'd share a little bit about it in the spirit of helping us make a wise decision.

Chase Devil, Tipton Weed, Klamath Weed, St John's Wort

St. John's Wort has been used for thousands of years medicinally and there is a long list of names attributed to it (the link is most likely not a complete list but a good indicator of its history).  The efficacy of it medicinally was tested recently in Germany and it has been tested in Canada as well.  There are several publications with information on its use as a medicinal herb that you can read for more information on it.

Reddish stems which will each hold several flowers

Hypericum perforatum is a stoloniferous herbaceous perennial that in winter can be seen as a rosette, the grouping of leaves and stems that surround the crown of the plant.  Its leaves are opposite of each other on the stem.  As far as I know there is not another weed in my garden that looks similar.

Little bits of light showing the perforated leaf, an important ID feature

If you hold one of the leaves up to the light you will see what appear to be little pin holes, thus the species name "perforatum".

The plant produces several flowering stems that grow between 2' to 3' tall but can get as tall as 5'.  Each flower produces seed by the hundreds with each plant capable of producing 100,000 seeds per year.  These seeds can persist in the soil for decades. (Knowing this, do you want it in your garden or not?)

It is important to note that this plant has had a negative impact, out competing native and foraging plants and is considered a noxious weed in at least 20 countries around the world.  However, it is cultivated as an herb for commercial purposes in some areas of south eastern Europe. (What to do, what to do...)

It can be controlled digging out plants when you see them or using herbicides such as 2, 4-D and Glysophate if needed.  As a biological control, Chrysolina beetle were introduced in the 1940s and have now become well established in helping battle this weed in the western United States.  These beetles feed on the leaves and flower buds and help to keep it from spreading unchecked.  This year was the first year I had seen them in my garden.

Chrysolina beetle in my garden are feasting quite happily this year.

Important to note is that this plant is poisonous to grazing animals such as cattle, sheep, goats and horses if they eat enough of it.

Personally I like the bit of yellow the blooms add to the garden, even if it is not refined in its appearance.  It is however a self sower and those seeds, hundreds in each seed pod and they last for decades in the soil so I'm never going to be completely rid of it...and if anything happens to me it will become a nightmare plant!  So I think I've made up my mind.  Have you made up yours yet?

With all of that said, don't you think we need to ask some very important questions here?  If it grows so readily do we even need to bother with it or will letting it grow in our garden only become a part of the problem?

So think about it; it may be useful but should we really be cultivating it or just wild harvesting if need be?  I'm not sure if this helped any of you, but I know I'll be pulling out all of mine. The way I see it is I can always harvest it in the wild which will also help keep it from spreading.  Happy Gardening!

NOTE: Be sure to always properly ID any plant before using it medicinally, especially if it is to be taken internally!

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  1. Hi Patty,
    Uggghhh.. ( said in a Charlie Brown voice) guess what I bought three of and planted in my garden this spring? Yup Hypericum 'Aubrey Purple'.
    Who knew? Obviously, not me.
    I wonder if I can return them.

    Great post,

  2. Karen...take heart dear. What you have does not seed around nearly as bad as its weedy cousin and is much easier to control. It actually was the most commented on plant in my garden during the garden tours I used to host here. I will do a post to demonstrate how to manage them.


  3. Oh! Glory be! I'm so glad my 'Aubrey Purple' might not try to take over the world...
    As for my 'Coronation Gold' yarrow, not that's another story...

    Thanks Patty, I look forward to that future post
    warm regards