Pick a Plant Day – Crazy Plants in My Garden – St Mary’s Thistle

Not quite another light and fluffy blog today… this one grew arms, legs and an attitude.  I surprised myself as to how passionate I felt about this discussion, but hopefully I’ve delivered a moderately balanced view. Endings can’t always happy – BUT perhaps this is not the end….

To continue on with my few short segments on the strange things I have found growing in my garden (in this case a memory of a few years back)…..  Hopefully you’ll find a few surprises amongst them and learn a little too!  Thanks go (yet again) to the guru who has planted many strange things over the years and found, by trial and error, which are the “fittest” for our climate and soil!

Exhibit A: Chilacayote (Cucurbita ficifolia) – See Previous Posts

Exhibit B: Bergamot (Monarda Citriodora) – See Previous Posts

Exhibit C: St Mary’s Thistle (Silybum marianum)

Wikipedia lists this gal’s common names as: cardus marianus, milk thistle, blessed milk thistle, Marian Thistle, Mary Thistle, Mediterranean milk thistle, variegated thistle and Scotch thistle as well as St Mary’s Thistle. (Picture Reference)

Similar to the Bergamot (Monarda Citriodora), the St Mary’s Thistle is a Dicotyledonous  (normally shorted to Dicots) which, as you will recall, refers to the group of plants which flower and whose seed has two embryonic leaves.

St Mary’s Thistle belongs to the Asteraceae Family of the Asterales Order within the Asterid Clade.  Members of the Asteraceae or Compositae (commonly referred to as the aster, daisy, composite, or sunflower family) are mainly herbaceous, but some are shrubs, vines, or trees. The family is found worldwide distribution, but most often in arid and semi-arid regions of subtropical and lower temperate latitudes.  (Reference)

Most of the members of the Cynareae tribe within the Asteraceae family are known as thistles.  The Silybum genus within this tribe is comprised of just two species:

  1. Silybum eburneum (or Silver Milk Thistle, Elephant Thistle, or Ivory Thistle) is native to Algeria, Morocco, Tunisia, Spain and prefers a sunny situation on moderately moist soil. Saying that, they can also tolerate temperatures down to -18°C. It has simple leaves that are alternate, denticulate (curated edge) and petiolate (attached to the plant by a stalk).  The plant produces solitary light-purple many-stellate flower. (Reference)
  2. Silybum marianum….. we’ve reached our topic for this week.

The two species hybridize naturally (produce a third different offspring from the combined gene pool of the two plants species), with the hybrid being known as Silybum × gonzaloi. (Reference)

St Mary’s Thistle is an annual or biennial that grows to 1.5-3.0 m tall (depending on who you believe!).  Unlike most crazy plants, this one’s visual beauty (Beauty No.1) lies in its leaves and leaf arrangement.  The large prickly-edged leaves covered with white veining, and stems containing a milky juice.  The thistle has a brilliant purple flower heads surrounded by sharp spines and grown at the end of long flower stalks – and, yes, its pretty striking too!

This was our lovely specimen from 2010/11 (okay, I’ve cheated, crazy plants photographed in my garden a few years back!):

1 Blessed Thistle (Large)

1 Blessed Thistle 3 (Large)

1 Blessed Thistle 4 (Large)

Just look at those incredible patterns in every feature of the leaf and flower!  It’s like Fibonacci just slapped us across the face…..And look at the amount of edge the plant has managed to create! (Permaculture Principles – 1. Observe and Interact, 11. Use Edges; Value the Margin)

Growing St Mary’s Thistle  – Beauty No.2 is the ease with which this plant grows…and I quote:

“Area of Adaptation – Milk thistle is native to western and central Europe and northern India, but has become naturalized by escaping from cultivation in southern Europe, Africa, India, China, Australia, South America, and in many parts of North America…Milk thistle is very drought tolerant and prefers dry well-drained soil in full sun. It is found along roadsides, in fields and waste places….

Weed Control – Milk thistle is often called a weed itself, and is a very good competitor. Hoeing and/or hand weeding in the early stages is the only requirement. (Note: Since seeds are wind dispersed, they may become a “weed problem” …. One solution is to cover each flower head with a mesh bag before the seeds mature. )

Insects and Disease – Milk thistle is not bothered by many pests, and no diseases have been noted. (I’d like to add here that although many look at the insects as a negative…. the hover flies particularly love it as does anyone belonging to the Animalia Kingdom (me, bees, butterflies, etc) that loves a good lookin’ flower! It also provides a ripper habitat and broad soil protection for insect life above and below ground.  In some references there are comments about snails and slugs, but it appears limited damage can be caused and only on young plants.)

Irrigation – Milk thistle is very drought resistant and should not require irrigation unless severe conditions arise.” (Reference – except for my commentary!)

Looks pretty gooPhoto of Silybum marianum (L.) Gaertn.d for our climate (and under my management)!  In fact if you look at the FloraBase website run by the West Australian Government (DPAW) you’ll get a feel for the conditions in which it thrives as well as some nice photos of less loved species and what the “fluffy pappus” looks like that we’ll learn about soon….Browse to the list of specimens for Silybum marianum (L.) Gaertn.



The Plants for a Future Website comments that it is “Suitable for light (sandy), medium (loamy) and heavy (clay) soils and prefers well-drained soil. Suitable pH: acid, neutral and basic (alkaline) soils and can grow in very alkaline soils.  It cannot grow in the shade. It prefers dry or moist soil. The plant can tolerates strong winds but not maritime exposure.” (Reference) So a broad range of soils, just avoid shade and salt spray – Check!

It can be in flower any time from late Spring, through Summer and into the start of Autumn depending on when the plant was germinated.  The seeds tend to ripen through to late Winter. The flowers are hermaphrodite (have both male and female organs – i.e. you don’t need two plants) and their pollination is dominated by Bees.

Why Grow St Mary’s Thistle  – Beauty No.3 is apparent when you look at the historical and current uses and research associated with the plant….however it comes with a “BUT”.

Whilst the plant has many functions and uses, theMilk thistle seeds - Click Image to Close

seeds hold the medicinal properties and hence drive commercial growing. “The fruit is small, hard, shiny, and grey to black (an achene) with a silvery pappus or fluff.” (Reference)

WORD of the DAY: ACHENE – An achene is a type of simple dry fruit from plants typically of the Asteraceae family, but not always.  Achenes contain a single seed that nearly fills the pericarp, but does not adhere to it.  I.e. A single seed which rattles around within a shell – think of the sunflower seed, the stripey part is the Achene and inside is the single unattached (except for one thread – like umbilical cord) seed: (Reference)

sunflowerSo I’ve been calling the wrong bit seeds all these years…. other Achenes are the “seeds” on strawberries, buckwheat, dandelions….

Back to topic….How are the “seeds” (a term used often synonymously with achene!) processed:

“Seed extracts are produced commercially in Europe[222].” (Reference)

“Seeds are ready for harvesting the first year… Heads should have finished flowering, and be cut with less than one inch of stem…..Mature seeds, which have the highest level of silymarin (the achene contains 1.5-3% silymarin), are found in seed heads showing abundant silvery white fluff (pappus)….The fluffy pappus must be removed from the “seed” (achenes). The “seed” is usually dried, powdered and made into a tincture using ethyl alcohol.  It is best to use 95% alcohol to extract the seed. Most of the silymarin is concentrated in the protein layer of the seed husk (pericarp). The tincture should be bright yellow, indicating the presence of the resinous fraction which contains the silymarin.”  (Reference)

seeds (Reference)


There are many different opinions about the validity of claims that the St Mary’s Thistle’s silymarin has medicinal properties.  I’ll cover the known issues first and then I’ll go through what is thought to be the benefits.  When trying to find information on benefits and issues, it was interesting to see the two sides of the coin…. one angle was crop development, the diametrically opposite being weed removal – same plant! I think I have captured enough to give you a flavour and perhaps a little food for thought.  I leave it to you to hunt through the literature and decide for yourself. Let the debate begin…..



“Milk thistle can produce allergic reactions, which tend to be more common among people who are allergic to plants in the same family (for example, ragweed, chrysanthemum, marigold, and daisy).  (It may also)… lower blood sugar levels. People with diabetes or hypoglycemia, or people taking drugs or supplements that affect blood sugar levels, should use caution.” (Reference)

“Because of potassium nitrate content, the plant has been found to be toxic to cattle and sheep. When potassium nitrate is eaten by ruminants, the bacteria in an animal’s stomach break the chemical down, producing a nitrite ion. Nitrite ion then combines with hemoglobin to produce methaemoglobin, blocking the transport of oxygen. The result is a form of oxygen deprivation.” (Reference)

When grown on nitrogen rich soils, especially those that have been fed with chemical fertilizers, this plant can concentrate nitrates in the leaves. Nitrates are implicated in stomach cancers. Diabetics should monitor blood glucose when using. Avoid if decompensated liver cirrhosis. Possible headaches, nausea, irritability and minor gastrointestinal upset [301].” (Reference)

“Very high dosage can cause loose stools because of increased bile flow. For those who have a sensitive digestive tract, begin with one capsule and gradually increase the dosage. If you experience loose stools or diarrhea, then reduce the dosage.” (Reference)


BENEFITS – Apologies for the repetition within this section, but I like to include the facts verbatim as I was obviously not at the clinical trials, nor did I do endless research to list the well grounded statements.  These people have done this to greater and lesser degrees and, as I say, it’s up to you to decide for yourself. Here are some opinions and references to follow.

Blessed thistle has a long history of use in the West as a remedy for depression and liver problems[254]. Recent research has confirmed that it has a remarkable ability to protect the liver from damage resulting from alcoholic and other types of poisoning[254]. The whole plant is astringent, bitter, cholagogue, diaphoretic, diuretic, emetic, emmenagogue, hepatic, stimulant, stomachic and tonic[4, 21, 160, 165, 238]. It is used internally in the treatment of liver and gall bladder diseases, jaundice, cirrhosis, hepatitis and poisoning[238]…. Silymarin, an extract from the seed, acts on the membranes of the liver cells preventing the entry of virus toxins and other toxic compounds and thus preventing damage to the cells[244]. It also dramatically improves liver regeneration in hepatitis, cirrhosis, mushroom poisoning and other diseases of the liver[222, 238, 254]. German research suggests that silybin (a flavonoid component of the seed) is clinically useful in the treatment of severe poisoning by Amanita mushrooms[222]…. Regeneration of the liver is particularly important in the treatment of cancer since this disease is always characterized by a severely compromised and often partially destroyed liver[K].  The German Commission E Monographs, a therapeutic guide to herbal medicine, approve Silybum marianum Milk Thistle for dyspeptic complaints, liver and gallbladder complaints (see [302] for critics of commission E).” (Reference)

infestation(Picture Reference)

“Milk thistle is proven to be effective in the treatment of hepatitis, cirrhosis (e.g. due to excessive consumption of alcohol) and jaundice, and in protecting liver cells against toxins such as mushroom poisons from the death cup fungus (Amanita phalloides), chlorinated industrial solvents, and acetaminophen or certain other drugs’ overdose or prolonged treatment. ” (Reference)

“Since silymarin is nearly insoluble in water, aqueous extracts or teas are ineffective for liver treatment.” (Reference)

“Today, its primary …uses include liver disorders such as cirrhosis and chronic hepatitis, and gallbladder disorders. Other … uses include lowering cholesterol levels, reducing insulin resistance in people who have both type 2 diabetes and cirrhosis, and reducing the growth of breast, cervical, and prostate cancer cells….Previous laboratory studies suggested that milk thistle may benefit the liver by protecting and promoting the growth of liver cells, fighting oxidation (a chemical process that can damage cells), and inhibiting inflammation. However, results from small clinical trials of milk thistle for liver diseases have been mixed, and two rigorously designed studies found no benefit.” (Reference)

Silymarin cream has been through clinical trials (via the Australian New Zealand Clinical Trials Registry) and was found to be a “safe new candidate effective treatment for melasma” (Reference).

It is interesting to note that back in 1997 Health Canada had registered several St Mary’s Thistle products and that the U.S. Pharmacopeia was reviewing its inclusion.  Further research reveals that Silymarin in the form of Milk Thistle Capsules is within the USP NF. (The United States Pharmacopeia and The National Formulary (USP–NF) is a book of public pharmacopeial standards. Reference 1, Reference 2)

You can buy it in Australia in many locations with sales statements like: “Apparently….helps create new, healthy liver cells without encouraging the growth of any malignant liver tissue that may be present. Silymarin, is also an antioxidant, protecting liver cells from damage by free radicals. This active ingredient can be used by healthy people who can expect to have their liver ready and able to detoxify damaging substances much easier.  Milk thistle also is believed to ease outbreaks of psoriasis.” (Reference) Please note that I’m not endorsing any products, but commenting on its general availability locally.

Other uses:

“De-spined leaves were used in salads, while stalks, roots and flowers were cooked. Seeds were used as coffee substitute. It has been used as a medicine for over 2,000 years as milk stimulant, for liver, kidney and spleen problems, for jaundice, gall stones, and menstrual pain.” (Reference)

“Root – raw or cooked[1, 2, 4, 52, 183].  A mild flavour and somewhat mucilaginous texture[K]. When boiled, the roots resemble salsify (Tragopogon hispanicus)[1, 4, 115].

Leaves – raw or cooked[1, 4, 5, 52, 89, 115]. The very sharp leaf-spines must be removed first[46, 183], which is quite a fiddly operation[K]. The leaves are quite thick and have a mild flavour when young, at this time they are quite an acceptable ingredient of mixed salads, though they can become bitter in hot dry weather[K]. When cooked they make an acceptable spinach substitute[238]. It is possible to have leaves available all year round from successional sowings[K].

Flower buds – cooked[1, 238]. A globe artichoke substitute[12, 183], they are used before the flowers open. The flavour is mild and acceptable, but the buds are quite small and even more fiddly to use than globe artichokes[K].

Stems – raw or cooked[4, 100]. They are best peeled and can be soaked to reduce the bitterness[5, 183]. Palatable and nutritious[4, 115], they can be used like asparagus or rhubarb[12] or added to salads. They are best used in spring when they are young[105].

A good quality oil is obtained from the seeds[4]. The roasted seed is a coffee substitute[21, 46, 61, 183]…..

A good green manure plant, producing a lot of bulk for incorporation into the soil[K].(Reference)

And to throw the argument upside down….Here is the BIG BUT…..In WA it is a declared weed.  Once we confirmed its botanical name through leaf and flower identification, we cut off and destroyed the flower and have elected to not grow it again… a very sad day. The description is: “When established it competes with more useful pasture plants for light, moisture and nutrients. Under certain conditions, variegated thistle is poisonous. It can kill cattle and, occasionally, sheep, especially when hungry animals consume large quantities in the absence of alternative feed. It becomes more palatable to stock – and more toxic – when it has wilted after cutting. It has numerous spines which may cause injury to animals, including domestic dogs. Variegated thistle is also an important contaminant of wool and the plant provides excellent cover for rabbits.” (Reference)

Close up view of variegated thistle showing the solitary purple flower head surrounded by long spiny bracts

I’ll say no more…..well except that perhaps removing St Mary’s Thistle should not be the first thing you do if your animals are left hungry enough to consume large quantities of it! Who am I kidding, of course I need to say more, but I’ll do my best to keep it balanced and contemplative.

Other plants that create the same problem are outlined here: “Nitrate in sorghums and other grasses – “Sorghum and other grasses – including oats (Avena sativa), ryegrass (Lolium spp.), maize (Zea mays), button grass (Dactyloctenium radulans) and liverseed grass (Urochloa panicoides) – can accumulate toxic amounts of nitrate. This is more likely when growing in nitrogen-rich soils (e.g. cattle camps, fertilised pastures) and when the plants wilt or the weather is overcast.  Other non-grass plant species which tend to be associated with cases of nitrate poisoning in livestock include pigweed (Portulaca spp.), mintweed (Salvia spp.), capeweed (Arctotheca calendula) and variegated thistle (Silybum marianum).” (Reference)

I guess this introduces a very brief statement about the required thought process and research which needs to be conducted when bringing a plant into a new area.  There is a fine line between farming and neighbouring farm infestations which we have touched upon with respect to the prevention of seeds being distributed by the wind.  Either knowingly or just thoughtlessly, the plant has been introduced to WA.  With all the positives outlined above related to ease of growth and I guess the very prickly nature of the plant (which I mentioned, but glossed over as, unlike hair prickles, you get a visual warning!), it is obvious how dangerous it might be in the Australian summer.  In an urban setting, cutting off the flower prior to the seeds maturing would mitigate the unintended spread of the plant – i.e. utilising international farming techniques (they bag the heads) to ensure responsible urban gardening.  It is also noted that high nitrate soils typically produced by chemical fertilisers increase the toxicity and effect of eating the leaves on our “hungry livestock” – bringing us back to how we treat our soil and how our soil treats us…    But that is another story and a much broader cause of problems.

In the not too distant future, we’ll do a general weed discussion which will cover some of the above in a general sense.  The idea being to look at identifying weeds, what the role of weeds play in nature, what our weeds are trying to tell us, what use we can make of our weeds and what happens in the tragic circumstance that you run out of weeds for your salad!

Before we concl1 Blessed Thistle 2 (Large)ude our discussion of this glamorous controversial gal, it needs to be mentioned that the determination of the botanical name for any plant you are studying needs to be established beyond doubt prior to assuming its edible, medicinal or ecosystem supporting properties.  This particular plant revealed to me how common names, especially within the thistle family, can differ between countries, states and even local resources. It’s easy to get confused between the blessed milk thistle and the blessed thistle (and it is obvious that many have!).  Whilst not at the opposite end of the medicinal spectrum in this case, the information was not right….  Do this with an alternate plant and you might find yourself an a lot worse a condition.  Hence my changing this post to be St Mary’s Thistle as that appears a common, but less confusable name for the Silybum marianum.

The best way to find what you need is to use one resource to identify one aspect of the plant and hence obtain potential botanical names.  In my case, I looked at the flower.  There are several examples of very similar flowers (Western Weeds – Hussey, B.M.J; Keighery, G.J.; Dodd, J; Lloyd, S.G. and Cousens, R.D.) but when checking the botanical names through internet sources it was evident that the leaves were not the same. So I then looked for the leaves and work back to the flowers from the botanical names identified.  Its great if you can also confirm the plant with the seeds, but it depends to what level of detail you need to go.

And so, the stunning looking and stunningly controversial St Mary’s Thistle qualifies for the Crazy Plant Section of this blog….. but wait til you see the next feature in this series! More flowers and more controversy to come….

The last month has been eventful – we’ve had the Soil Hugger’s inaugural public appearance, acceptance into regenerative agriculture research (things are gonna get technical!) and almost two full weeks of 2015 event planning….. I’ll up date the events page of this blog as activities solidify, but needless to say there’s heaps to do in the Year of the Soil  – too many worth attending both as an eager listener as well as those I hope to assist in the presentation of.

Remember, if there is an edible plant, soil, Permaculture or a related topic you’re curious about (or I have promised and not delivered on!), put in a request and we can add it to the blogging list.  There is so much to explore!

Still to come in this particular series….

Exhibit D: The Lion’s Tail or Lion’s Ear or Klip Dagger

Exhibit E: The New Guinea Bean

Exhibit F: Wild Passionfruit

Exhibit G: Slipper Gourd

Exhibit H: African Cucumber

Until then, enjoy.


3 thoughts on “Pick a Plant Day – Crazy Plants in My Garden – St Mary’s Thistle

  1. Pingback: Pick a Plant Day – Crazy Plants in My Garden – Slipper Gourd | The Soil Hugger's Journey

  2. Pingback: Pick a Plant Day – Crazy Plants in My Garden – Klip Dagga (Leonotis Nepetifolia) | The Soil Hugger's Journey

  3. Pingback: HAPPY WORLD SOIL DAY (DECEMBER 5TH) | The Soil Hugger's Journey

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