Prickly sow-thistlePrickly sow-thistle

Name: Prickly sow-thistle
( spiny annual sow-thistle, spiny-leaved sow-thistle, spiny milk-thistle, spiny sow-thistle )

Latin name: Sonchus asper L.

Occurrence: Prickly sow-thistle is a troublesome annual or overwintering weed common on arable land. It is also found in gardens, on roadsides, waste places and other disturbed habitats. It is recorded up to 1,500 ft in the UK. Prickly sow-thistle grows on most soils but prefers well drained slightly acid to alkaline soils, and has some tolerance of saline conditions.

In a study of seedbanks in some arable soils in the English midlands sampled in 1972-1973, prickly sow-thistle was recorded in 53% of the fields sampled in Oxfordshire and in Warwickshire. Prickly sow-thistle seed was found in less than 1.5% of arable soils in a seedbank survey in Scotland in 1972-1978. In seedbank studies in arable fields in France, prickly sow-thistle was well represented in the seedbank and in the emerged vegetation.

A number of ecotypes and varieties of prickly sow-thistle are described but environmental conditions also influence the appearance of the plant. It is generally less abundant than the smooth sow-thistle, S. oleraceus.

Prickly sow-thistle has been used as a potherb since ancient times. It is host to various aphids and acts as a reservoir to several important plant viruses including beet western yellows.


Biology: Prickly sow-thistle flowers from June to October. The flowers are self-compatible. Mature seeds (achenes) are formed 1 week after flowering. The average number of seeds per flower head is 198, and a plant often has over 100 flower heads. Seed numbers per plant generally range from 21,500 to 25,000 but a large plant may have 60,000. In a competitive cereal crop a plant may have just 500 seeds. Moisture stress also reduces the number of seeds formed. Prickly sow-thistle can be found in fruit for 3 months of the year.

Seeds germinate from spring to autumn. Light and stratification at low temperatures stimulate germination. Seeds on the soil surface germinate better than those buried at 30 mm deep. Seedling emergence occurs from March to November, with peaks in March-April and August to November, but odd seedlings can germinate at any time. Spring emerging seedlings reach the rosette stage after 6 weeks. This is followed by flower bud formation and stem elongation.


Prickly sow-thistlePersistence and Spread: The half-life of seeds in cultivated soil is just 1 year while in dry storage it is 2-3 years.

The plumed seeds are normally wind dispersed and seeds have been collected by aircraft at 2,000 ft. Under damp conditions the pappus of hairs collapses and dispersal is prevented. The seeds are eaten by birds and viable seeds may be found in their droppings. Viable seeds have also been found in cow manure. Prickly sow-thistle seeds ingested by earthworms have been found intact in the worm casts. The seeds have been recovered from irrigation water. Prickly sow-thistle seeds have been found as a contaminant in clover, grass and cereal seeds, particularly in home saved cereal seed.


Management: Seeding should be prevented by cutting, pulling or hoeing the plants before flowering. However, plants that are cut down early in the year can produce further flower stalks. In pasture, prickly sow-thistle may be controlled by grazing with sheep or mowing.

Tillage and surface cultivations in spring and the inclusion of root crops in the rotation should keep the weed in check. Regular cultivations will help to deplete the seedbank.

Direct heating of prickly sow-thistle seeds in soil reduces viability but high temperatures are needed to kill seeds relatively quickly. The seeds are susceptible to soil solarization.

Prickly sow-thistle is attacked by a range of insects.

Updated October 2007.

Further Information / Links:

For more information on this weed

»UK farmers' case studies

« Back to Annual Broad-leaved Weeds

Comments

  1. I tried to pull a thistle up out of my yard and I must have got something in my hands, because they are just stinging and I can't get them to feel better. What can I do to get these thistles out of my hands.
    - Sharon 2---0-2006

  2. i have got something that looks like mosquito bites on my arm from pulling stinging weeds up. what is the remedy to get rid of them?
    - shirley malabar 6---0-2006

  3. I have fought with these weeds in my garden and along my home for a couple of years. I pull them, hoe them, put weed killer on them. They continue to return. What can I use to get rid of them once and for all.
    - Susan 7---0-2006

  4. After picking prickly sow-thistle weeds around my yard, I have bumps on my arms similar to poison ivy, and it itches just as bad as poison ivy. Wear long sleeves if you're going to pick these weeds!
    - Matt Oliver 9---0-2006

  5. Thistle reacts on me like poison ivy. I just have to lightly touch it & I will have it spread systemically through my body for two weeks. I can actually watch new "bubbles" appear on my skin in hours.
    I try to remember to use Technu Lotion after weeding (used for posion ivy sap removal). The best thing is to take Benadryl capsules & lather on Calagel. If it's on your legs-make sure you sleep in pj's-this stuff spreads EASILY-especially if you scratch & open the blisters.I also suggest you pay CLOSE attention to what you handle in plant stores and nurseries-they DO NOT pull these weeds from their plants-as I found out last Sunday-I am covered from head to toe in rash. The other place to watch out for thistle is if you go strawberry picking-the fields are LOADED with thistle. I don't think you ever get immune to this stuff-if anything-it gets worse! If anyone has found a really good remedy for this please list it!
    - Helen 9---0-2006

  6. Paul harvey advertises a product called zanfel a poison ivey cream. expensive..costs $45 but I'm telling you it is worth it!! You scrub with it until the itching stops...usually under a minute and the rash immediately starts to celar. I too was covered with a rash from those thistles!!! tried benadryl, washing with technu..nothing worked until i tried this stuff!!
    - ann 0---1-2006

  7. I have thistle in me yard ( 2 acres ) and of course it seems to thrive when it gets very dry and the grass doesn't grow. I found that by using Roundup and spraying it at the base of the thistle will allow the Roundup to be absorbed into the thistle through the roots and it then dies. You have to be careful to just put the Roundup at the base because if you over spray, it will kill the surrounding grass also. I found using an eye dropper ( DO NOT USE IT FOR ANYTHING ELSE ) let me get it right to the base and the grass then filled in after the thistle died. You should see it start to die within a couple of days. Good Luck.
    - Bruce 0---1-2007

  8. thistle, the bane of my gardens existence. pull it, dig it out, squirt it, nothing works. a few days later, more seedings pop up their little heads. oh, what to do?
    - mary 5---0-2008

  9. My first experience with thistle came when I moved down to Florida. It also gave me a skin rash very similar to the rash I develop from poison ivy. Because my skin is so sensitive, I've had the opportunity to try many forms of relief including going to the doctor for a steriod treatment (before I knew how to identify the assailant)! To those who are ailing, aside from possibly seeing a doctor, I recommend Band-aid Itch Relief spray. It cools, it works, it dries, and it provides relief long enough to almost forget the itch. As for the weed itself, what can I say, the spotting and pulling of weeds is the price we pay for being discriminate about what is in our garden. This thistle is perfect for a wildflower garden when trying to attract butterflies.
    - Karen 7---0-2008

  10. I just discovered that I have an allergic reaction to the prickly thistle and have the same reaction to it as poison ivy. I found out the best remedy to relieve the itching is a hair dryer! Just start the hairdryer on hot and direct the heat to the rash for as long as you can tolerate it! ( usually about 10 sec). I'm not kidding!! I believe the dryer releases histamines and the itching stops. I do this only twice a day and I find it the best remedy that takes away the itch!! Doesn't hurt to try... I suggested this to my friends and they also had amazing results!! Now... would love to find out how to get rid of those thistles!! Janis
    - Janis 9---0-2008

  11. I pulled out some prickly sow-thistle and got a few needles stuck in my thumb. It's very tingly and is beginning to feel like pins and needles in my entire thumb.
    This is very annoying as I can not even see the needles to pull out!!
    I've looked around and have yet to find a remedy for this annoying problem.
    Is there anything besides waiting it out?
    - Sarah 1---1-2009

  12. did anyone come up with a cure for that damned rash caused by this weed?
    allen@grindandbrew.com if they did...PLEASE!
    - allen 1---1-2009

  13. I searched the internet high and low for the solution to this "EVIL" plant or weed whatever it is... I too found myself insane for both the constant vigilance to protect my yard and landscaping and this uknown rash that seemed to coincide with the weekly yard duties. I progressively got worse until I figured out what had caused my woes,unfortunately I had been weed-wacking them and also inhaled this noxious and bitter odor that literally closed my throat. I ran into my house and used my asthma inhaler and I was slowly able to feel better. Later that day I was not able to breathe in deeply.I felt a burning that lasted for 4 days. In hind-sight I suppose I should have gone to the ER,but I'm alive and scared to death of those plants! RASH RELIEF=BENADRYL TOPICAL GEL...(carry some with you for a while) ALLERGY MED. LIKE BENADRYL CAPSULES AT BEDTIME... CHANGE YOUR SHEETS AND PJ'S EVERY NIGHT FOR 3-5 DAYS... AND DEFINETELY STAY COOL...SWEAT MAKES IT 1,000 TIMES WORSE AND UNBEARABLE. I hope this helps someone because it certainly was a journey of "trial and error" for me. Good luck. P.S.= I wore long industrial cleaning gloves and a particle mask, then I took the top off to expose it's hollow core and mixed weed-killer with a tiny bit of lime powder and funneled it down the core (stalk) and watched their very timely death 1 by 1. I hope their perminantly gone!!!
    - John in Ct. 1---1-2009

  14. I find when I pull thistles out of the ground and get some in my
    fingers.....even through the rubber gloves...I simple "wash" my
    hands...especially the part with the thistle...with soft, dry dirt....
    it seems to work like a miracle...and comes out every time...
    once I pulled a dry thistle, accidentally, while pulling up another
    weed and got a handful of thistle...the dirt worked so well I have never forgotten it.
    - jean 1---1-2009

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