If you want to add it to an existing herb bed then the best way is to sink a deep bucket or tub without holes into the soil and plant into that as otherwise mint will quickly choke out the other plants. Apart from that, mint is not a fussy plant and will even grow under trees or in shade.Click to see full answer. Similarly, it is asked, what will kill mint plants?Many people have had luck using boiling water to kill mint. Others swear by using a homemade mixture of salt, dish soap and white vinegar (2 cups salt, 1 teaspoon soap, 1 gallon vinegar). Both methods will require frequent applications onto the mint over some time in order to kill it.Beside above, does Mint spread in the garden? Growing at 4 inches per month, a single plant would spread to 2 feet in about six months. However, as the rhizomes creep away from the original plant, new plants are created, increasing the size of the mint area. Spearmint, which is more vigorous than peppermint, has an even faster growth/spread rate. Regarding this, can Mint rust spread to other plants? At first it will just be a few spots but soon, if it’s not treated, it will spread over the whole plant as well as any other mint plants in the garden. Mint that has been infected with rust cannot be eaten. Eventually the leaves will die and drop off and the plant will become stunted.Are there poisonous mint plants?4 Answers. However; also from wikipedia, i believe the poisonous variety mentioned in the comments is mint variety Perilla frutescens – Which while it appears it is not poisonous to humans, it is toxic to cattle & horses.