Marigolds are best known for helping control nematodes, a kind of worm that can be destructive to plants. However, claims that marigolds can kill fungus, insects and selective weeds have been exaggerated, writes Lee Reich. In reality, marigolds have little actual benefit in suppressing disease and above-ground insect pests, except maybe to attract insects away from other plants. Marigolds might be most useful because they look pretty, Reich adds.
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