Nightshade purple flowers
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That is called deadly nightshade or black nightshade, and can run rampant throughout your garden in one season. It contains atropine and can cause issues with the heart if enough is ingested.
The best and fastest way to get rid of it without chemicals is to pull it up, bag it and put in the garbage. Since yours already has berries, wear gloves, long-sleeved shirts/pants and protective glasses (clear plastic glasses that encompass the entire eye). With the rainy weather, the earth may still be soft and it will be easy to pull. If not use h a shovel or water around the plants to soften the earth. It should come out easily. It does not have a tap root rather a web of roots. Pull everyone you see. Don't put in your compost pile.
If that is not what you want to do you can use 30% vinegar. This is an organic herbicide but definitely needs to be handled with care as the fumes if inhaled can burn you. Please follow the instructions on the bottle. It is for sale at most garden stores - 1 gallon. Put it in a 1 gallon sprayer full strength and add two tablespoons of vegetable oil to get it to stick to the leaves. Shake and spray, however you may need to spray the plants a few times - spray it when it is sunny and hot like today - around 58-60 degrees.
These plants are from seeds from last year's plants. Therefore even if you get all of the plants this year, you may still have new ones next year. However, I have been able to rid the lawn and gardens at my place by pulling them. At least at this time, I have none!!
Remember that nighshade is a poisonous plant and can irritate the skin so please wear gloves, and the protections listed above. If you do feel you got some of the berry juice or plant on your clothing or skin, wash thoroughly as soon as possible.
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