How to control weeds in the garden?

An Introduction to Invasive Weeds

Weeds can be a major headache for gardeners, especially when they are invasive and difficult to control. One such notorious weed is Canada thistle. However, it’s important to note that Canada thistle is just one example of many invasive weeds that gardeners may encounter. Whether it’s tiger grass, fire grass, bindweed, or any other aggressive weed, the key is to tackle it head-on and not let it take over your garden. In this tutorial, we will explore different methods to control weeds in the garden and how to manage these tenacious weeds?

The Downside of Cardboard Sheet Mulching

One method that many gardeners try is cardboard sheet mulching. The idea is simple – by laying down layers of cardboard, the weeds underneath are smothered and deprived of sunlight. However, when it comes to Canada thistle, there is a significant drawback. This weed is communal, meaning it can spread through its root system. Even if you cover it with cardboard, if there is a small gap or insufficient coverage, the weed will find a way to grow and thrive. This method may work for some weeds, but it is not effective against the resilient Canada thistle.

The Limitations of Vinegar Spray

Another popular method is using vinegar spray as a weed killer. Vinegar is a strong acid that can be effective against certain weeds, but not against Canada thistle. Again, the communal nature of this weed makes it difficult to control. Killing one plant only leads to another one sprouting nearby. The real problem lies in the roots, which store the energy created by photosynthesis. Spraying vinegar on the foliage may cause the plant to wither and die temporarily, but it won’t prevent new shoots from emerging. Therefore, vinegar spray is not an effective solution for Canada thistle.

The Disappointment of Cornmeal Gluten

Cornmeal gluten is an organic option that inhibits root development in broadleaf weeds. It is affordable and readily available. However, it falls into the category of pre-emergent herbicides. Pre-emergent herbicides, like cornmeal gluten, prevent seed germination and root development. While it can be effective against weeds before they emerge, it does not control root development after the plants have already sprouted. Unfortunately, this means that cornmeal gluten is not effective against Canada thistle. Using it may seem like a solution, but it will ultimately disappoint and waste time and money.

The Power of Physical Removal

After trying various methods with no success, the final and most effective way to control Canada thistle is through physical removal. While this may seem obvious, many gardeners don’t stick with it long enough to see results. Simply cutting off the plants once will not solve the problem. The remaining roots will continue to sprout new shoots, leading to more plants. However, continuous physical removal is the key. By diligently removing any growth, even the tiniest bit, every single day for an entire growing season, the root system starts to lose its energy. Eventually, the weed will be under control, and the garden will be free from the relentless invasion of Canada thistle.

Preventing Future Invasions

While it’s important to know how to control invasive weeds, it’s equally crucial to prevent them from entering your garden in the first place. There are three potential ways these weeds can infiltrate your garden:

1. Bird Seed

Be cautious if you have bird feeders or if your neighbors do. Bird seed often contains weed seeds, including thistle seeds. Birds can scatter these seeds in your garden, leading to the growth of invasive weeds. While it’s lovely to attract birds, be aware of the potential risks associated with bird seed.

2. Tainted Mulch

When using wood chip mulch, especially free mulch, there is a risk of it containing weed seeds or root fragments. Some companies don’t thoroughly screen their mulch, allowing tiny root fragments to find their way into your garden. These fragments can grow into invasive weeds and cause a headache for gardeners. Always be cautious when using mulch and ensure it is from a reliable source.

3. Tainted Compost

Compost is an excellent way to enrich your garden soil, but it’s essential to be mindful of its source. If the compost contains yard waste or decomposed weeds, there is a high chance of weed seeds or root fragments being present. While a well-heated composting process can kill most weed seeds, it’s not foolproof. Dormant seeds or fragments can still survive and resurface once added to your garden. Therefore, it’s crucial to know the source of your compost and avoid composting any weed material.


Dealing with invasive weeds like Canada thistle can be a challenging task, but it’s not impossible. By understanding the limitations of various methods and adopting a persistent approach to physical removal, gardeners can regain control of their gardens. Additionally, being proactive in preventing future invasions by being mindful of bird seed, using reliable mulch sources, and being cautious with compost can save a lot of time and effort in the long run. Remember, it’s crucial to stay vigilant, be persistent, and not turn a blind eye to the presence of invasive weeds. With determination and consistent effort, you can reclaim your garden from these tenacious invaders.