Do you know the best time of year to apply weed control to those pesky perennial broadleaf weeds such as Dandelions and Canada Thistle?
a. Early Spring after germination at pre-emergence
b. Spring at emergence while weeds are young
c. Summer when weeds are at their prime
If you chose the last option – you are correct!
In fall, perennial broadleaf weeds transport food (carbohydrates) from their foliage to their roots in preparation for winter. Broadleaf herbicides applied in fall are absorbed by the weed’s foliage and transported to the roots along with the carbohydrates, resulting in the destruction of the broadleaf weeds. Perennials such as thistles and dandelions are best controlled from mid September to early October.
There is one catch when you apply weed control in the fall – weeds won’t die within a few hours or even overnight, unlike in the spring, when you may observe curling of leaves within hours. In the fall the process happens much more gradually. Depending on soil conditions and the volume and type of weed, plus it’s hardiness, you may not see any visible signs of it dying off before winter.
In Alberta, some hard to kill weeds like Canada Thistle, are easier to control in the fall. After applying weed control you won’t see much change in the fall, but by the time the snow melts in the spring the weeds should be gone or at least the majority of them.
At Green Oasis we use a specially blended formulation that is a combination of fertilizer and weed control. Depending on the state of your lawn and yard, and the volume and types of weeds that need to be controlled, we may recommend a single application or up to 5 applications. The number of applications we recommend will also vary depending on how green you would like your lawn to be.
Early May Nursery and Garden Centers, October. The Best Time To Control Weeds In Your Lawn
Iowa State University, Yard and Garden: Applying Herbicide and Fighting Fall Weeds
Canola Watch, What is the Best Time for Fall Weed Control?