Companion plants are often considered of value to the garden as a result of their ability to repel garden pests. For the most part, however, companion plants are of particular value because of their ability to attract and to maintain populations of pest predators. A major problem is that a lot of the information about the use of companion plants has never been documented. An effort will be made to spell out if the particular use of a companion plant does or does not have supporting data. There is very little data supporting this practice.
Self pollination is when pollen is transferred from the male to the female parts on the same flower.
Cross-pollination is when pollen from one plant is transferred to another plant of the same species. The resulting offspring from cross-pollinated plants are more vigorous and seemingly more disease resistant. Plants produce nectar which attracts insects to them so that the flowers can be pollinated. There are many insects that are attracted to this nectar and in the process pollinate the flowers. Bees, as a group however, are unique in that the nectar is their base source for carbohydrates and the pollen is their base source of fat and protein.