At first glance, a plant with pretty blue flowers may look nice in your garden or yard, but soon those little blue flowering plants may take over. Attractive or not, if it is growing where you do not want it, it is a weed. Many of these weed plants reproduce by reseeding and can produce hundreds of seeds from one plant. You will probably need to spend a good deal of time removing these invasive weeds, or learn to live with them.
The tiny, five-petal, sky-blue flowers of the field forget-me-nots (Myosotis spp) may look pretty in your garden until the plant begins to reseed itself and becomes invasive. Classified as an annual, this pretty little weed has shallow roots and can be easily hand pulled or spaded out. Each flowering plant can produce 700 to 1,500 seeds, and the seeds can remain dormant for several years in the ground before germinating. Remove the plant before it flowers to stop the development and releasing of seeds.
Native to North America, wild violets (Viola papilionacea) frequently become bothersome in a homeowner's lawn or garden. A hardy perennial, wild violets have attractive blue to blue-purple, five petal flowers, with either white or yellow centres. Growing from rhizomes, wild violets are difficult to control or eliminate unless the tedious work of hand digging out the roots and rhizomes is undertaken. Herbicide products containing glyphosate can be applied repeatedly to wild violets with limited success.
Often found in lawns, waste areas, and nursery stock, Persian speedwell (Veronica persica) is a low growing, sprawling winter annual weed that blooms small, four-petal, bright-blue flowers. Preferring cooler, shaded areas, Persian speedwell propagates and spreads by seed. Because the weed is a broadleaved, repeated application of a broadleaved herbicide over time will eliminate the plant from your lawn or landscape.
Often found in pastures throughout the southern States, perilla mint (Peri indicutescens (L.) Britt.) can be an invasive annual. Highly toxic to livestock, the plant should be eradicated in the spring or early summer by mowing before it can develop flowers and reseed itself. The small, whitish-blue-purple flowers appear in cluster spikes in the late summer.