By Michelle Scullard, Master Gardener
I garden so I can spend the summer pulling weeds – said no gardener ever. Weeds challenge the best gardeners. They emerge early in the season along with crocuses and daffodils. Just like flowers and vegetables, weeds grow at different times of the season. Some weeds, like the one you may recognize below, are viewed by some people as beneficial, while others consider them worse than a plague. This weed, the dandelion, can be eaten in salads and dandelion wine packs quite a punch.
Gardeners do need to control or manage weeds because they compete for water and nutrients. They block out sunlight and airflow, promoting plant diseases. They can also grow so vigorously that they crowd or choke out the plants we want to grow. They cause vegetables and flowers to grow smaller and decrease the vegetable harvest. It is important to spend the time removing them or preventing them from growing.
Controlling and managing weeds requires knowledge of the particular weed (Controlling Weeds in Home Gardens). To identify the weed, the University of Minnesota Extension has a weed identification site, Is This Plant a Weed? You can use the pictures to identify the weeds and then learn about their growing habits and optimal methods for controlling them. Using a pre-emergent can prevent many weeds from growing. Manually pulling weeds and using a hoe or cultivator is another good method to manage weeds. Mulching is an excellent method for minimizing weeds and has the benefit of adding nutrients to the soil as the mulch breaks down. Some people will use landscape cloth as another barrier under the mulch in flower beds or landscaping. Use of herbicides may control weeds, but need to be used very carefully to prevent damage to plants you want to keep such as flowers or shrubs.
Let’s look at a specific weed example – thistles. There are several varieties of thistles that grow in Minnesota, including the Canada Thistle, the Bull Thistle, the Perennial Sowthistle, Musk Thistle (also known as Nodding Thistle), and Plumeless Thistle. They may be difficult to distinguish between as they have similar characteristics. Thistles are a particularly persistent weed. They are difficult to eradicate and can spread quickly. One reason they are problematic to remove is their root system. Many have a deep tap root with underground stems (rhizomes) that is extremely hard to remove entirely and they quickly regenerate if any part of the root remains underground. As with all weeds, getting rid of them before they flower is critical – even though the flower might be considered pretty.
Methods to remove thistles include carefully and slowly pulling the whole long tap root out. Make sure to wear thick gloves to protect your hands from the spiny, prickly tips. Repeatedly mowing or cutting them down at ground level may yield success but has to be done repeatedly to ensure they do not flower. These two methods require constant vigilance and may take several years to achieve success. Many gardeners resort to targeted chemical applications of herbicides. The specific herbicide used will depend on the location of the thistles – in the lawn or flower beds. Herbicides should never be used in vegetable beds. The University of Minnesota Extension website (Control Options for Common Minnesota Lawn and Landscape Weeds) provides suggestions for treatments, with different approaches for lawns and non-lawn locations. It may require multiple applications to eliminate the thistles.
You have to stay vigilant and watch for new growth and treat it. Users are cautioned to carefully read and follow all instructions on the label of the herbicide being used. With persistence, thistles and other weeds can be managed. Working on eliminating them as soon as you notice them will reduce the amount of time and energy you have to expend and give you more time to enjoy your garden.
Thistles and other weeds can be annoying but you can beat them with a little research and a lot of persistence.