How to get rid of 'black wart weed (similar to a milkweed) but monarch butterflies do not like it?
You need to dig it up and keep digging it up as fast as possible before it regrows.
Dig them up and don't let them flower. or make seed.
Pour hot water and vinegar over it. This should kill it off.
Common name "Dog Strangling Vine". It's a toxic plant, highly invasive, 2 types of Swallowart & are part of Milkweed family,Monarchs do like it but mistake it for the Milkweed they need for survival, lay eggs then larve is poisoned by toxins in plant killing off Monarchs. ROUND-UP is what you need to use. Here's other options https://efotg.sc.egov.usda.gov/references/public/MN/797SwallowWort..pdf Be persistent in removal it's important to irradicate any invasive plant species wherever you live.