All bean enrich the soil with nitrogen fixed from the air. In general they are good company for carrots, brassicas, beets, and cucumbers. Great for heavy nitrogen users like corn and grain plants. French Haricot beans, sweet corn and melons are a good combo. Keep beans away from the alliums.
Improves growth and flavor of carrots and tomatoes . Chives may drive away Japanese beetles and carrot rust fly. Planted among apple trees it may help prevent scab. A tea of chives may be used on cucumbers to prevent downy mildew.
Plant as a barrier around tomatoes, radishes, cabbage, cucumbers, and under fruit trees. Deters wooly aphids, whiteflies, squash bug, cucumber beetles and other pests of the cucurbit family. Great trap crop for aphids (in particular the black aphids) which it does attract, especially the yellow flowering varieties. Likes poor soil with low moisture and no fertilizer. It has been the practice of some fruit growers that planting nasturtiums every year in the root zone of fruit trees allow the trees to take up the pungent odor of the plants and repel bugs. It has no taste effect on the fruit. A nice variety to grow is Alaska which has attractive green and white variegated leaves. The leaves, flowers and seeds are all edible and wonderful in salads!
Plant among and sprinkle on tomatoes, and asparagus. Use as a tea to ward off asparagus beetles. Attracts hoverflies. Let some go to seed to attract the tiny parasitic wasps. Parsley increases the fragrance of roses when planted around their base.
Plant with tomatoes to improve growth and flavor. Basil can be helpful in repelling thrips. It is said to repel flies and mosquitoes. Do not plant near rue.