Multi-purpose plants

From Appropedia

One of the principles of permaculture is that every plant should have multiple uses (at least 3? Is this the same as "Stacking Functions"?^{[verification needed]})

As well as the obvious and important use of providing food in various forms, they may provide other functions, like:

herbs, which add a lot of flavor and pleasure to the experience of eating, make simple and healthy food taste better (which can save money through buying more simple, basic foods rather than pre-prepared flavored foods), are best used fresh from the garden, and are best available on a whim, rather than having to plan and buy ahead.
insect repellents: some herbs also repel insects.
shade: under a fruit trees can be a great place to sit, especially in summer.
companion plants: This is the belief/principle that certain plants grow better together.
enriching the soil, through nitrogen fixation, organic matter or encouraging soil organisms
attractive and fragrant flowers and leaves.

Plants which are well known for one purpose sometimes have other valuable uses which are neglected. For example:

Plants known for their fruits sometimes have leaves and shoots which are appetizing and healthy as vegetables, for example chayote, grape, some varieties of squash