- How to Get Rid of Thistle Permanently
- Yes, REALLY Tough Weeds Like Thistle and “Running Bamboo” CAN Be Beaten!
- Getting rid of thistle in 3 steps
- Creeping thistle
- Thistles: A High-Nutrient Weed
- Getting Rid of Thistles with Vinegar: Green Gardening Tips
- Controlling Canada Thistle – Canada Thistle Identification And Control
- Canada Thistle Identification
- How to Get Rid of Canada Thistle
How to Get Rid of Thistle Permanently
It’s tough, it’s spiny, it’s hairy, and it’s taking over your yard. Thistle—whether it’s of the musk, tall or Canada variety—is a very difficult weed to eliminate from your lawn or garden once it has taken hold; a single musk thistle can generate 120,000 seeds from one flower, and can grow to six feet tall. Eliminating thistle for good my take several years, because thistles are either biennial or—even worse—perennial. If you have thistle one year, you will have even more the next, unless you take action. Biennials, such as musk thistle and tall thistle, germinate in summer and fall, spend the winter as rosettes, then produce many flower heads the next spring. The fluffy purplish flowers of thistles are the only visually pleasing part of the plant, but don’t be fooled; they carry the seeds that guarantee another year of thistle invasion. Canada thistle, a perennial, reproduces in the same way, but it has the added advantage of spreading by way of its roots; this makes control even more challenging.
If you want to banish thistle, you have to go to war against it. Fortunately, you do have some weapons at your disposal.
Yes, REALLY Tough Weeds Like Thistle and “Running Bamboo” CAN Be Beaten!
Question. Mike: A neighbor planted ‘running’ bamboo as a “natural fence” around his property, and not surprisingly, it’s out of control. The culms are about 12-16 feet high; both plant and root system are invading my property. It also blocks out the sun and sucks up all the available water so that I can’t seem to get anything else to grow in my backyard. I’ve read that bamboo is technically classified as a “perennial grass” which means that growing it violates a township ordinance requiring grass and weeds not to be higher than 10 inches. If the township orders it to be removed, how do we get rid of it safely without damaging the environment? Thank you.—Curtis in Cherry Hill, NJ.
Hello, Mike McGrath: What can you recommend to get rid of thistles in my garden and lawn? I have tried extreme weeding and professional chemical treatment, but they’re back!!!!!!! Thank you.
- —Valerie, Rockville, MD
style=”font-weight: bold;”>Answer. These are two of the toughest weeds you can face, especially the bamboo, which ‘runs’ at an astonishing rate and will happily take over acres I fallowed to— although your terminology is somewhat off, Curtis. Those aren’t plants AND roots invading your domain—its one big plant with one giant honkin’ root system that expands to cover the earth like horticultural concrete a few inches under the surface. Some thistles form similarly impenetrable root systems. (Val— never let thistles flower; if you do, then you’ve got roots and seeds to worry about!)
These are not easy plants to beat, and as Val discovered (Bad girl!), toxic chemical herbicides won’t do the trick. Those poisons are good at killing off single plants, but they don’t affect huge underground root-systems; so don’t waste your time, money and life fooling around with them.
There are three basic ways to do the job well and safely, all of which involve you first cutting the above ground growth to the ground repeatedly. Cut it all down, allow it to grow again; cut it all down again, let it grow again, etc. Two, three, four times; the more the better to deny the roots their solar energy collectors. In fact, if you just do this continual cutting for several years, the plants and roots will eventually die.
For more immediate satisfaction, cut and then do one of the following:
- 1. To kill a patch on your property alone, mulch, mulch, mulch the entire area with something THICK and HEAVY (sheet-metal, old carpeting …) weighted down with a few inches of soil or woodchips on top. May be soak the area with a high-strength vinegar (see #3) first. Make sure the mulch extends a good couple of feet past where the plants were growing. Regardless, the root system will likely send plants out on a scouting mission and try to creep up around the edges. Be vigilant, and mulch these pioneers and/or spray them with high-strength vinegar. Leave the mulch in place for at LEAST a year. Or better still, leave it there forever, and make a nice raised bed filled with ‘wanted’ plants over top. READ COMPLETE ANSWER
- 2. If the bamboo is spreading to your property from a neighbor’s place and you just want to keep it on their side, cut yours down and drive barriers deep into the ground at the property line to keep more from spreading over. Then use high-strength vinegar and/or mulch to kill the roots on your property.
Here’s some barrier info from one of our favorite sites, www.Americanbamboo.org (this is also a great place to learn more about bamboo—not all types are bad; there are many well-behaved varieties that grow in tidy clumps): “To prevent running bamboo from spreading, a “rhizome barrier” two or three feet deep is essential. It should be slanted outward at the top so that when the rhizomes hit the barrier they will bend upwards. A barrier does not stop a running rhizome; it only deflects it. The barrier should project an inch or two above ground level. Check the barrier once a year, and cut off rhizomes that arch over the top.
“Barriers can be concrete, metal, or plastic. The usual recommendation is high-density polypropylene (40mil or heavier), glued, taped, or clamped with stainless-steel at junctions. This material comes in rolls or as hinged sections, and is available from some landscape suppliers and bamboo nurseries, frequently termed root barrier. More elaborate barriers with corner posts that hold the material at the proper angle are also available.” McG: We don’t need more plastic in the world, so I strongly suggest metal instead of the poly.
Essentially what you’re doing here is building an underground fence, and before you can build that fence you’ll have to dig a trench to hold it. (Unless you have John Henry illusions, rent a machine to do the job.) And, if you make it wide enough; say a foot across; that trench alone will make an excellent bamboo barrier. Even better, turn your problem into a water feature! Dig a deep trench in between you and the bamboo/thistle/other super weed and then fill it with water and make it a kind of canal running along your property. Put in some fish and some a quatic plants and you’re happening! (Like vampires, these weeds can’t cross over running water.)
Cut everything down, wait till the soil is bone dry and no rain is predicted for at least a few days and then, in the heat of the day, soak the earth containing those unwanted roots with one of the products below. (Be careful; you must wear protective gear, especially safety glasses). The high acidity of the vinegar will lower the soil pH down to something like 3—the surface of the moon. All plant and soil life will die, earthworms and larger creatures will quickly run or squirm away and that region will become a dead zone. Leave it like that for at least a month—longer if you can. (And if you fear that ‘your’ plant has more lives than Christopher Lee in an old Dracula movie, do it again a week or two later.) When you’re sure it’s really most sincerely dead, raise the pH back up with wood ashes or lime to between 6 and 7 (use teststrips or a meter) and soil life will return and the ground will be fertile again— but the roots will stay dead.
“Burn out weed killer” is St. Gabriel’s Labs mixture of vinegar and lemon juice; it now also contains clove oil and is called “Burn Out II”(the sequel!)— but this is for normal weeds; it’s not strong enough for things like thistle or bamboo. They recently introduced a double-strength version called “Poison IvyDefoliant” that should do the job. St. Gabe’s products are available at retail outlets or direct from them at 800-801-0061; www.milkyspore.com.
“Green sense 20% acidity vinegar” is white vinegar that’s four times more potent than the household variety. (“You watch the weeds die.”) Its available in some retail stores in the Southeast, and Rohde’s in Garland, Texas (near Dallas) will ship you a gallon for $11.95 plus $8.50 shipping; call 972-864-1934, or visitwww.beorganic.com and enter “white vinegar” in the search function. (There’s a photo at www.greensense.net) Although, this stuff is incredibly powerful, it is all-natural—and not all high-strength vinegars are. The folks at Rhode’s stress that their Greensense product is a grain based vinegar, not a petroleum-based product like the Acetic Acid used in photography. Once it’s done its work, a grain-based vinegar will return its nutrients to the earth, and allow life to colonize the soil once again. Chemically produced acetic acid will leave toxic resides that will destroy soil life for perhaps years to come; don’t use them.style=”font-weight: bold;”>SAFETY NOTE: All of these products require extreme caution on the users part, especially the 20% vinegar! This is not harmless stuff! Vinegar with such enormous acidity is really caustic! You have to be careful not to get any on your skin or eyes–gloves and goggles are a must!!!!
And that, dear readers and listeners, is why many of you asked Rhode’s to come up with something a bit gentler, and they did. (And yes, they tell us, it was entirely at the request of YBYG listeners, from whom most of their mail-order sales come! Thank you, Rhode’s!) The new creation is “Greensense 10% Acidity vinegar”; $7.95 plus $8.50 mail order. You’ll have to use it more than once (the 20% is like dropping a ‘natural nuke’ on those roots), but it is much safer to handle. “You pays your money and you takes your choice.”
“Greenergy Blackberry & Brush Block”, 8% vinegar (apple cider or wine) and 5% citric acid, is a West Coast product (apparently, wild blackberry vines attack people’s cars and children out there). You can get a gallon from Professional Turf Center in Portland for $36 (includes shipping); call 1-800-894-7333(Regular household 5% white vinegar will only kill ‘easy’ annual weeds.)
You Bet Your Garden ©2004 Mike McGrath
Getting rid of thistle in 3 steps
Q uestion: How can I get rid of thistles in my ground cover? I do not want to kill off my ground cover. It is on the hillside in front of my house. The area is very sunny. Full sun almost the whole day. The ground cover is very thick. It has small, needle-like leaves and is low to the ground. I can’t remember the name of it but it’s very old and took a long time to fill in. Please help. I don’t want to rip it out and start over, but it is beginning to look like my only option.
Answer: Getting rid of any weeds in ground cover is problematic, but thistles present an extra challenge. Not only do thistles spread via seed, their thick, white roots also spread underground, causing new plants to pop up on a regular basis. Weeds that spread in this fashion should never be tilled or the problem will become worse as each root piece the tilling process leaves behind will develop into a new plant.
A few months ago, I wrote a column on how to manage thistles in an empty garden bed, but managing them in a ground cover is a whole different ballgame.
No matter what weed you’re dealing with, when it grows throughout a bed of ground cover, I recommend following these steps.
1. Never let the weed set seed. Whether it’s grass, clover, bindweed, or thistles, it’s important to not let the weed’s flower turn into seed. Doing so will only make the problem far worse. Even if it means you chop down the weeds with a string trimmer or loppers every week or two, it will prevent seeds from being produced. It also weakens the weeds over time, making it easier to control.
2. The second step in controlling weeds in ground covers is to hand pull them religiously. While this task isn’t easy, it’s crucial to controlling the weed population. Even if you don’t get every bit of a weed’s root out, you’ll be weakening the plant, and with repeated top-killing like this, the weed is eventually starved of carbohydrates and dies. It may take a season or two, but going out and weeding the ground cover bed on a weekly basis makes a huge difference.
3. You can also target-apply organic herbicides to the weeds. The brands I most often recommend are Avenger and BurnOut (both of which are available from various online sources, including Amazon and planetnatural.com). The trick with using these products in ground covers is always to apply it just to the weeds and not to the ground cover itself. These products do not discriminate and will kill any plants they come in contact with. To target the application, put on a chemical-resistant glove and then soak a sponge with the herbicide. Hold the sponge with your gloved hand, and wipe it up the weed, from its base to its top, squeezing the herbicide onto the plant’s leaves and stems. This keeps the herbicide off the ground cover. You may have to repeat this process a few times in order to eliminate all the weeds, but it is very effective.
As with all herbicides, it’s important to follow label instructions carefully. Organic herbicides are often based on acetic acid which can be very caustic to skin, so heed all the precautions on the label.
A combination of all three of these steps, done in a consistent fashion, will clear your ground cover of its weedy visitors.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to [email protected] or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.
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Creeping thistle flowers from July to September, sometimes into October. Normally each plant bears only functionally male or female flowers. The male flowers produce abundant pollen. The fragrant female flowers are insect pollinated but the pollinators may only visit one type of flower. Plants within a patch formed from a single clone cannot self fertilise and little seed may be set in some instances. The maximum distance between male and female clones that still ensures seed set has been estimated at 50 to 390 m. Occasional plants may be found with hermaphrodite flowers and these can set seed freely.
The time from flowering to seeds becoming viable is around 8-10 days. There is some variation because seed in the outer florets matures earlier. At 8 days, around 13% of seeds are viable, at 9 days 80% and at 16 days 90%. Plants cut down in flower produce very few seeds and none are viable although they appear normal. Seeds ripen from June to September and are shed from August onwards. There may be 20 to 200 seeds in each flower head and an average of 680 seeds per stem. The seed number per plant ranges from 1,600 to 50,000.
Some seeds can germinate on dispersal other are dormant but this may vary with ecotype. Seed is shed largely in autumn and chilling over the winter leads to germination in spring but seedling emergence at other times is not precluded. Seed shed in July-August may germinate the same autumn. Seed has been found to germinate on the soil surface but the optimum depth is 5 to 15 mm, although, emergence has been reported from up to 60 mm deep. Light, nitrate and alternating temperatures can interact to promote germination. Seeds germinate best at relatively high temperatures.
Thistle seedlings are sensitive to drought and early competition for light. They are unlikely to survive in dense stands of other plants. Seedlings require soil disturbance to become established in standing vegetation. Autumn germinated seedlings may not survive if they have made insufficient root growth before the foliage is killed by frost. Spring emerging seedlings, 19 days old and with 2 true leaves, were able to regrow after removal of top-growth. At this stage the branched root system is up to 15 cm long. Seedlings develop a taproot with spreading laterals within 8-10 weeks of emergence. Adventitious buds develop at the base of these side roots. Once these are formed a seedling is able to regenerate readily if hoed off. Some of the buds grow upwards to form leafy shoots others develop as rhizomes. Seedlings undergo a juvenile vegetative phase but can emerge and flower within a year.
The deep-seated creeping root system is very brittle and easily breaks into pieces. Although the roots may penetrate several metres down, most regeneration is from roots within or just below the plough layer. It is only the thickened areas of root and the underground stems that are able to regenerate and form new plants. Regions of the lateral roots thicken due to the development of storage tissue and it is here that new shoots are initiated. Fragments shorter than 2.5 cm do not always regrow but segments 5-6 cm in length or longer regenerate readily. Regeneration is less successful in November.
Creeping thistle food reserves are minimal between May and July. After flowering, assimilates pass down into the underground organs from July to October to build up reserves for the following year. The plant dies down to just below soil level in the late autumn. Some of the underground organs may also rot away leading to fragmentation of the parent colony into separate units of swollen roots. In spring, shoots that developed on the storage roots the previous autumn grow to the surface and develop into the new aerial shoots. Adventitious roots develop on the shoots and some swell to form the perennating organs for the following year.
Field and glasshouse studies suggest that residues of creeping thistle are phytotoxic to the growth of other plants including some crops. Water extracts from the roots and foliage have been shown to inhibit plant growth.
Thistles: A High-Nutrient Weed
Thistles are a bane of picnickers and campers. Who hasn’t trodden on the sharp, unforgiving spines of a thistle when out and about barefoot in grasslands? For many people, relationships with thistles have generally been painful and irritable, but now you can get your own back!
One of the great things about thistles is that every single species is edible, so this is great news for foraging beginners! Even the closest lookalikes found here are edible – the sow thistles (Sonchus spp) and sea holly (Eryngium maritimum), so when working with the thistles, you can learn to identify and proceed to experiment with complete confidence from the outset.
We have at least 14 species of thistle growing wild in the UK, mostly from the Cirsium (aka plume thistles) and Carduus genera. Thistles are found in numerous settings all over our islands and can be a useful soil barometer. Often their presence signifies that the land is fertile, and in many instances, neglected.
I eat from a number of different species. These are: creeping thistle (Cirsium arvensis), spear thistle (C.vulgare), woolly thistle (C.eriophorum), marsh thistle (C.palustris), and welted thistle (Carduus acanthoides syn C.crispus). As you will discover, plants that have spines to offer protection against predators, have no real need for bitterness.
It’s almost impossible to misidentify a thistle. One of the easy-to-spot botanical differences between thistles and their numerous relatives in the daisy family, is that the overlapping bracts (involucre) found directly below the flowers of thistles, are always spiny. Simple!
The leaves of the numerous species will differ in size, shape and the density of spine coverage. Most have stiff spines on the margins, but some have soft prickles. You need to discover for yourself which are the more tactile!
When in flower, most thistles produce a lovely purple / mauve bloom, but some species are known for their yellow inflorescence (cabbage thistle – Cirsium oleraceum and the Carline thistle – Carlina vulgaris).
In all of the thistles, flowers give way to copious amounts of fluffy hairs (pappus) attached to their tiny fruits, superbly designed for air-borne dispersal. A distinguishing feature between the two main genera is that Cirsium spp produce feathered pappus hairs, whereas Carduus spp only have simple pappus hairs.
Creeping thistle produces dense spines on its leaves, but very few spines or hairs on the flowering stems. Spear thistle has large, deeply-lobed leaves with large spines at the margins, as well as hairy, spiny stems.
Marsh thistle looks somewhat like spear thistle at an initial glance, but without the large spines and leaf lobes, and usually with a thin, red, leaf margin. Woolly thistle is easily identifiable with large, deeply-lobed, evenly-shaped leaves, and very large flower heads, wrapped in a ‘cobweb’ of cotton-like hairs.
This particular species is the largest wild thistle I use, although if you have milk thistle (Silybum marianum) growing in your plot, you can use that too, but you will need good gloves to protect yourself from its long spiny flower heads! Eating milk thistle chokes would of course prevent you harvesting the exceptional liver-supportive medicine found in the seeds.
Where to find thistles
Creeping thistle will grow in all manner of waste-ground, grasslands, verges and field edges. I also see a lot of spear thistle in similar habitats, although when found in grassland, it’s not as abundant as the creeping species. The root systems explain why; spear thistle has a tap root, whereas creeping thistle grows on rhizomes.
The marsh thistle, as its name alludes to, likes damp conditions such as fens, marshes, canal tow-paths and riversides. Woolly thistle is a little bit more selective in its choice of soil and setting, preferring calcareous ground. It too enjoys grasslands. Welted thistle can be found all over the UK, especially loving clay soils.
Go prepared! Stiff gloves and a knife are required. Harvest the best leaf mid-ribs in spring when growth is plentiful and quick. Your specimens will be tender and sweeter.
Flowering stems will appear from late spring through into autumn. I only consider harvesting from plants whose flower buds are yet to really begin unfurling. Flower buds (chokes) are available all summer.
Nutritional value of thistles
In Portugal, a number of thistle species are still collected in spring and sold at markets. A recent academic study highlighted the nutritional value from eating thistles. The findings are contained within ‘Ethnobotany In The New Europe’ by Manuel. P de Santayana et al (Eds), published June 2010.
In the study, researchers noted the wide range of thistle species collected, and concentrated on the nutritional value of one particular thistle (Scolymus hispanicus – Spanish or golden thistle). This plant is collected by villagers in various areas of the countryside. Bunches of the stripped leaf mid-ribs are sold and bought in a number of markets in different areas.
Levels of certain nutrients were analysed and compared to some commonly consumed vegetables. Their findings show that the thistle contained consistently higher levels of important major nutrients than some of our commonly consumed cultivated vegetables.
Weight for weight, thistles come out higher in fibre, protein, phosphorus, magnesium, calcium, copper, zinc, and other nutrients.
Is it likely that the thistles found wild here will be similarly endowed with a range of important vitamins and minerals? I’m more than happy to work on the assumption that this will be the case. Many other wild plant species are known to contain high concentrations of important nutrients.
How to use thistles
Preparing thistles is pretty easy. Simply choose the most tender specimens. If using the petioles, then cut and strip all the spines off, before peeling the outer, fibrous layer from the stalk. Use raw as crudités, pickle or ferment them, or chop into salads and serve them with a tangy vinaigrette. If cooking, they don’t require long!
Preparing the stems is similar, but they are hollow. These can be used in similar ways to the petioles, or you can stuff them, roast them, and braise them.
As relatives of the globe artichoke (Cynara scolymus), thistles produce edible, if smaller, ‘chokes’. These are the crunchy, immature bases, or capitulum, of the composite flower-head. As you would do with globe artichokes, peel away the bracts to get to the prize. I only choose the largest wild species for this.
Thistles are included in my new foragers playing cards, which feature 52 colour photos of temperate zone edible wild plants. They are ideal presents for plant lovers in any temperate climate! The decks are available, along with my new 2016 wild plant guide calenders, from [email protected]
Forage the three-corner leek
The ubiquitous dandelion: medicine, food & wildlife forage
The Wild Wisdom of Weeds
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Getting Rid of Thistles with Vinegar: Green Gardening Tips
Getting rid of the thistles in my gardens, lawn, and rock border always proves arduous for me during the spring and summer months. I live across from an open field, so the thistle seeds just keep floating onto my property, sprouting more and more prickly weeds. My husband and I tried pulling the thistles out by hand, but the task was tedious at best and painful at worst. Even with thick gardening gloves, the prickles on the weeds poked into our skin. Because I am allergic to most plants, I always broke out with itchy, red welts whenever I got poked by a thistle thorn. I needed a better solution to my thistle problem.
One day while perusing my Pinterest feed, I happened across a pin about using household vinegar to get rid of weeds in a stone path. According to the writer at A Garden for the House, spraying regular old vinegar on the weeds kills the plants without the use of harmful chemicals. Vinegar is a herbicide that is truly biodegradable. As a food, I knew that I could use vinegar around my house without worrying about the dangers to my daughter and pets. I was excited to have possibly found a solution to my weed problem that was truly safe for my family. Vinegar is also quite a bit cheaper than chemical herbicides.
After buying a few huge bottles of vinegar and a spray bottle, I proceeded to spray the weeds and grass taking over the rock border and path in the front of my house with straight vinegar. I sprayed every plant that I saw: grass, dandelions, violets, wild flowers, thistles. The next day when I went outside to check on the progress, I was thrilled to discover that many of the weeds were yellowed and wilting. Even more to my surprise, most of the thistles looked completely dead. I sprayed everything again that second day for good measure.
On the third day, I went outside and discovered that most of the small thistles that I had sprayed with vinegar had died and completely disappeared. Excited about my discovery, I started spraying all the thistles in my grass and taking root around my trees. After just one application, the majority of the thistles in my yard disappeared. I had killed the evil thistles taking over my property with a little kitchen vinegar and without the need to pull the prickly little weeds up!
The only caveat to using vinegar as an herbicide is that vinegar is not selective. Any plants sprayed with the vinegar will yellow and possibly die. As I quickly discovered, not only did the thistles in my yard die, but the grass around the thistles yellowed considerably. Fortunately, grass is pretty hardy. Unlike the thistles, the grass is still in my yard, just more yellow in color than usual. I am keeping an eye on the progress, but I expect the grass to make a come back eventually. However, in the battle against thistles, I am more than happy to sacrifice a little of my grass.
As for other weeds, the vinegar herbicide works okay. The other plants in my rocks are slowly dying. With multiple applications, I suspect that the weeds in my rocks will disappear completely too. However, for thistles, vinegar is also an immediate death sentence. Even if none of the other weeds die, I am still happy with the results of the vinegar on the thistles. If you too have a thistle problem in your garden or yard, try a little white vinegar. You will not be unhappy with the results!
Thistles in Rocks
Weeds in Rocks
Thistles in Grass
To recap, vinegar is an environmentally-friendly method for killing thistles and other weeds in gardens, grass, and rocks. Simply pour some undiluted distilled white kitchen vinegar into a spray bottle. Spray the plants that you want to kill with the vinegar. You may need to spray the plants a few times over a few days depending on the hardiness of the plants. Be careful about spraying other plants as vinegar is not selective and will harm any plants sprayed. After spraying the weeds, rinse the bottle out with water to avoid corrosion. Vinegar is a safe, simple, and effective herbicide, especially against thistles.
What other safe methods have you discovered that work to kill weeds around your house?
Getting Rid of Thistles with Vinegar: Green Gardening Tips © 2013 Heather Johnson
Thistle in Rocks © 2013 Heather Johnson
Spraying Thistle with Vinegar © 2013 Heather Johnson
Thistle Dying from Vinegar © 2013 Heather Johnson
Thistle Destroyed by Vinegar © 2013 Heather Johnson
Weeds in Rocks © 2013 Heather Johnson
Spraying Weeds with Vinegar © 2013 Heather Johnson
Weeds Yellowed from Vinegar © 2013 Heather Johnson
Weeds Dying from Vinegar © 2013 Heather Johnson
Big Thistle Dying from Vinegar © 2013 Heather Johnson
Thistle Wilting to Death from Vinegar © 2013 Heather Johnson
Thistles in Grass Dying from Vinegar © 2013 Heather Johnson
Dead Thistle in Grass from Vinegar © 2013 Heather Johnson
Yellow Patched in Grass from Vinegar © 2013 Heather Johnson
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Controlling Canada Thistle – Canada Thistle Identification And Control
Perhaps one of the most noxious weeds in the home garden, Canada thistle (Cirsium arvense) has a reputation for being impossible to get rid of. We won’t lie to you, Canada thistle control is difficult and requires a significant amount of effort to be successful, but the effort you put into controlling Canada thistle will pay off when you have a garden that is free from this annoying weed. Let’s look at how to identify Canada thistle and how to get rid of Canada thistle.
Canada Thistle Identification
Canada thistle is a perennial weed that has soft green, deeply lobed, spear-like leaves and these leaves have sharp barbs on them. If allowed to go to flower, the flower is a purple pom-pom shape that will be produced in clusters at the top of the plant. If the flower is allowed to go to seed, the flower will become white and fluffy, much like a dandelion seed head.
How to Get Rid of Canada Thistle
When starting a Canada thistle control program, it is best to first understand what makes Canada thistle such a difficult weed to control. Canada thistle grows on an extensive root system that can go quite deep into the ground, and the plant can grow back from even a small piece of root. Because of this, there is no one and done method of Canada thistle eradication. Whether you are controlling Canada thistle with chemicals or organically, you will need to do so repeatedly.
The first step towards getting rid of Canada thistle is making your yard and garden less friendly to it. While Canada thistle will grow anywhere, it grows best in soil with low fertility and open areas. Improving your soil’s fertility will weaken the Canada thistle and help desired plants grow better and, therefore, make them better able to compete with the Canada thistle. We recommend having your soil tested at your local extension service.
Chemical Canada Thistle Control
Canada thistle can be killed with weed killers. The best time to apply these is on sunny days when the temperatures are between 65 and 85 degrees F. (18-29 C.).
Because many weed killers are non-selective, they will kill anything they touch, so it is best not to use these on windy days. If you need to treat Canada thistle where it is close to wanted plants, you might be better off using a paintbrush to paint the weed killer on the Canada thistle.
Check back weekly and reapply the weed killer as soon as you see the Canada thistle reappear.
Organic Canada Thistle Control
Controlling Canada thistle organically is done with a sharp eye and an even sharper pair of scissors. Find the base of the Canada thistle plant and simply snip it off at the base. Do not pull Canada thistle out, as this can split the root, which causes two Canada thistles to grow back.
Check the location weekly and snip off any new growth that you may see. The idea is to force the weed to use up its energy reserves by regrowing but removing the new leaves before the Canada thistle has a chance to build its energy reserves back up.
Note: Chemical control should only be used as a last resort, as organic approaches are more environmentally friendly.