What vegetables should not be planted together?
The main considerations about planning a garden space should be light, soil, and water. It is important to make sure that there is adequate space for your plants to grow and that they do not shade one another. There are no hard and fast rules about plants that cannot be planted together, although there are some good practices to remember. It is a good idea to rotate crops each year so that you reduce the potential for diseases and pests to develop, and that rotation should extend to members of the plant family. So, if you grow cabbages in an area, it is important to remember that broccoli, cauliflower and Brussels sprouts are related. If you choose to plant these kinds of plants together in the garden, there is a risk that an insect or a fungus could jump from one plant to the next. Cucumbers, Pumpkins, Cantaloupe and squashes are all members of the same family (Curcubitae spp.) and can be devastated by the same bacterial wilt carried by the cucumber beetle. It is also important to consider pollination. If you have heirloom tomato plants and plan to collect the seeds, you need to plant them far enough from other tomato plants that they will not be cross-pollinated.
Although there are numerous “companion planting” lists available, most of these planting suggestions are not scientifically proven. They can be fun to incorporate into a garden design, but do not worry too much about them. However, we do know that black walnut trees product an enzyme in their roots that inhibits the growth of certain plants. Tomatoes, potatoes, and peppers are all very sensitive to this, so it is advised that you not plant this kind of garden near black walnuts. You should also avoid planting an apple tree in an area where there are cedar trees. There is a disease called Cedar-Apple Rust that requires both these types of plants to complete its life cycle. Other than that, let good gardening practices be your best guide.