Canada Thistle

For Canada Thistle, water regularly and deeply once a week during the growing season (spring and summer). Make sure to check soil moisture before watering to ensure the plant is neither too wet nor too dry. Avoid wetting the leaves, as this may increase the risk of certain diseases. During periods of extreme heat, water more frequently but reduce the amount given each time. In the winter, water only occasionally and just enough to moisten the root zone.

Canada Thistle (Cirsium arvense) needs direct sunlight for optimum growth. The plant needs full sun for about 6 to 8 hours per day. It is important to provide it with as much sunlight as possible to ensure maximum flowering and growth. If possible, provide the Canada Thistle with a south-facing location, which offers maximum sun exposure. In addition, the plant should be given a few hours of shade during the hottest parts of the day so that the plant does not become stressed or dehydrated.

Canada Thistle should be pruned in late fall or early winter after the plant has become dormant. Pruning should be moderate, removing no more than a third of the plant’s growth each time. Cutting back to a bud will help to prevent regrowth of the plant, as any part of the root left in the soil is capable of regrowth. Cutting deeply into the plant and removing as much of the root as possible will ensure that the Canada Thistle does not sprout again. Along with cutting, consider applying a pre-emergent herbicide prior to pruning susceptible plants. This will help reduce the sprouting of new Canada Thistle plants.