Good observation should tell you this is not true. Japanese beetles may feed voraciously on marigold blooms, and spider mites can kill marigold plants in mid summer. The truth is marigolds may help control some nematodes (microscopic worm-like organisms) that damage the root systems of plants, but only certain species of marigolds are effective in this regard. If you are going to plant marigolds in your garden, do it because you like the blooms.

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