Most people have heard that you are supposed to rotate your garden plants between plants from the same family. Many people have heard of companion planting where you plant certain plants together for a better harvest. However, few people have heard of vegetable plants to keep separated.
For example, do not plant cool peppers next to hot ones. Our family learned this the hard way when my Dad planted all his peppers in one row of the garden. One day he came in carrying a load of banana peppers. Now, my father likes very spicy peppers. My mother and sister do not. Dad offered the banana pepper to my sister, promising it was not hot. She took one bite, spit it in the sink and started crying. Turns out the hot peppers cross pollinated with the cool peppers and created one hot banana pepper. Forty years later, my sister still won’t eat banana peppers.
Cucumbers cause another problem. They cross pollinate with a lot of plants, such as squash, pumpkins, and melons. If you plant any Cucurbit near a cucumber, the resulting vegetables will look odd and taste bad. For example, planting cucumbers near yellow squash leaves you with yellow squash that are elongated and taste bad. Cucurbits need to be planted at the far corner of the vegetable garden to keep cross pollination from happening.
Herbs sometimes have problems playing nice together, too. For example, dill and fennel do not like each other. Plant them together and you get a plant that is not dill. The plant isn’t fennel, either. It is somewhere in between and tastes nasty.
If you are going to save seeds from your plants, make certain you have planted vegetables in the same family as far away from each other as possible or your seeds will not produce the vegetable you expected. Planting several heirloom tomatoes? Keep them well separated or they won’t breed true for you. It would be a shame to waste your heirloom seeds by planting them too close to others in the same family.