You need to understand that not all plants are appropriate for a companion planting with thyme. The list of plants to avoid is as follows: 1. Green onions. This species prefers drained soil. But planting thyme should be carried out in sandy soil. 2. Basil. If thyme prefers to grow in dry soil, then basil should be watered abundantly. 3. Cilantro. Not the best companion plant for thyme would be cilantro. It also prefers to grow in moist soil, which makes it different from thyme. 4. Fennel. Fennel bushes are poor companion plants for thyme, as it has a too strong aroma. 5. Parsley. Like basil and cilantro, parsley prefers to grow in a moist environment. This is the exact opposite of thyme.