Marigolds for Nematode Control: Living Plants Beat Extracts

What the Research Shows

French and African marigolds release compounds from their roots that suppress root-knot nematodes and certain soil-borne pathogens. However, studies on marigold root extracts are inconclusive—no definitive evidence proves they work as well as living plants.

Proven Method: Cover Crop Approach

1. Plant a solid block of marigolds 2 months before your nematode-susceptible crops (beans, okra, tomatoes).
2. Allow them to grow vigorously.
3. Till the entire planting into the soil before setting out vegetables.

This green-manure technique leverages the living root system's continuous chemical output and adds organic matter. For reliable nematode suppression, stick with the cover-crop method rather than relying on commercial extracts.