Yes, Roundup will kill them. I had to carefully spot spray them when they tried to take over one of my flower beds--had to cover all my "good" flowers with pots to protect them from possible over-spray. It got rid of most of them but I'm having a few more pop up here and there--they are quickly zapped with the Roundup.
I empathize: we're infested with wild violas here as well. When they come up near a desirable plant, and can't be dug out without messing up the good plant's roots, I apply Roundup with a sponge; works well and doesn't risk damage to the plants you want. Wear rubber gloves since you're not supposed to expose skin to Roundup.
Round Up is such a wicked evil nasty thing. It is wrecking havoc with the environment every where it is used. The Monarch population has dwindled severely because the genetically altered Round Up resistant corn allows for spraying of the herbicide on corn fields and the native supply of Milkweed is being killed off and... Have you ever tried a propane fueled weed torch? How about straight vinegar? How about just digging and pulling out the NJ State flower where you don't want it growing? Is the violet really a thug that calls for such heavy artillery?
I agree with you on herbicides, LadyCleo, and avoid them whenever possible. I have dug out hundreds and hundreds of wild violets, but must miss some of the tiny roots because they always reappear. Where they surface right up against a desired plant, digging isn't practical. I've tried straight vinegar for other problems with little success, but am happy to try it again with the viola. Please understand that I'm not talking about the occasional violet I would be happy to ignore. Our entire property of about an acre has them growing everywhere: throughout the lawn (don't care, just mow them down), in all the garden beds, coming up all over the gravel driveway, etc., etc. I'm sorry, but I'm just not willing to turn the whole place into a monoculture of wild viola.
I heard once that violet infestation is a pH problem.
Fix the acidity and you eliminate the violets.
I have tons of violets also, and to be honest, I've never tried pH altering remedies.
But it's something to think about.
That's interesting; I hadn't heard that soil ph affects violet viability. We seem to get them everywhere here, from good soil that's been amended for planned plantings, to what used to be crop soil when this was a farmhouse, to pure southern clay. Somehow they even manage to come up in areas where I've laid newspaper ten sheets thick to kill weeds, then covered that with mulch. Pretty hardy little plant.
I have plenty of wild violets in my garden and yes they are very annoying when they grow right through the crown of a special plant but they are the host plant of many fritillary butterflies. I continually remove the violets that are growing in the wrong place and allow the ones at the edge of the beds to grow. It seems it's the late summer that the eggs of the fritillaries are deposited near the violets for the spring hatching larvae. In the early summer, when the leaves are tallest and heavily eaten by the larvae, I have a hard time not cutting them down for the flush of new leaves. I just sit on my hands until I can't stand it any more. I have been rewarded for my tolerance by an increasing amount of fritillaries. If you can't get rid of the violets you might at least be encouraged by the fact you are helping the butterflies. Unfortunately if you do resort to using pesticides the remaining violets will not support the larvae because you will poison them as well as the plant.
Good to know, sempervirens: thanks! The butterflies are welcome to all the violets that come up all over what passes for a lawn here; I only object to them in the garden beds, and try to evict them there as soon as they appear. If I don't, they get out of hand in no time! Hopefully I'm pulling them before the butterflies find them.
I have never noticed any butterflies of any on any of my violets. I wonder why. I don't spray them or much in the area until later in the summer when some types of insects become problems on the veggies I grow in the flower beds.
leaflady, It is later in the summer when the eggs are laid near the violets so if you spray then you are killing the next generation. I see the results of the larvae chewing on the leaves of the violets in late spring. They look positively ratty with holes throughout. The fritillaries I see on the nectar plants in large numbers late in the season ( the asters in particular are always covered in butterflies). If I didn't have the violet leaves for the larvae stage to eat I wouldn't have the butterflies later. They need both types of plants to succeed- host and nectar.
Thank you for the information, Semper. I don't spray my flower beds. I use Kill A Bug directly on ant hills/colonies and ammonia right on individual slugs. Other than that I only spray the veggies being affected by the particular insect. Often they are ground dwellers(squash bettles for the most part)and I can kill them individually and drench the soil around the base of the plant with insecticide so no violets or other flowers should be affected. I don't like to spray general areas if I can avoid it.
Eat them! Violet leaves are chock full of vitamins and have a mild baby spinachish taste. The flowers are also edible. I use both in salads. After a point, if you keep removing the leaves, the plants have to die, since there won't be anything photosynthesizing.