Tagetes is commonly used in companion planting for which reason?

Tagetes, commonly known as marigolds, are particularly effective in companion planting due to their ability to deter nematodes, which are microscopic roundworms that can cause significant damage to plant roots. The roots of Tagetes exude substances that are toxic to certain nematodes, thus helping to protect neighboring plants from these pests. By incorporating Tagetes into garden layouts, growers can create a natural pest management strategy, reducing the reliance on chemical nematicides and promoting healthier plant growth.

While the other options highlight various benefits that companion plants can offer, such as increasing crop yield or enhancing flavor, it is the specific nematode-deterrent capability of Tagetes that makes it particularly valuable in a companion planting context. This unique characteristic not only helps protect individual plants but can also contribute to overall soil health, making it an important practice in sustainable horticulture.