There are a number of different types of weeds that have small purple flowers, so the process for managing them depends on the type of weed. Some types of weeds with purple flowers include Creeping Beggarweed, Doveweed, Japanese Clover, Canada Thistle and Wild Violet.
Other weeds that may have purple flowers include Creeping Charlie, Henbit, Narrow-leaf Vetch and Black Nightshade.
Some of these weeds are quite easy to control, as they can either be pulled out by hand or killed with an herbicide. This includes Black Nightshade, Wild Violet, Henbit, Creeping Charlie and Canada Thistle. Applying a thick layer of mulch to the garden can also help to prevent these weeds from growing in the first place.
Many types of purple-flowered weeds, such as Dovetail, can be stopped from growing by using a pre-emergence herbicide. However, once the plant has started growing, the only way to kill it is to use a non-selective herbicide like Round-Up. Extra caution should be used when applying a non-selective herbicide, as these products kill any plants that they come into contact with.
Commonly used for horse and cattle feed, Japanese Clover is quite difficult to kill once it has reached maturity and is capable of producing seeds. The plant can be pulled up before it reaches maturity, otherwise it is usually necessary to apply a pre-emergence herbicide to keep the seeds from germinating and the plant from returning the following year.