I have recently been researching what is best to plant under fruit trees. Traditionally many people have grass with a clear patch immediately below the trees as most fruit trees are relatively shallow rooted and it is thought that grass, and most other plants, will compete with the tree.
Following my Permaculture Design Course (PDC) I planted a low growing comfrey under my apple trees and some of my fruit bushes and I regularly cut it back leaving it to mulch the soil. The thinking behind this is that comfrey has deep tap roots and is a mineral accumulator, drawing minerals up from the clay further down and making it available to other plants with shallower roots. It also mulches the soil keeping in moisture.
Another advantage of the comfrey is that it’s flowers attract beneficial pollinating insects so when the fruit trees and bushes come into blossom there are already the appropriate insects around.
One disadvantage I recently read about in an article was that plants growing under fruit trees can harbour higher concentrations of INA (Ice Nucleation Active) bacteria, that is, bacteria which help to induce the formation of ice when it is cold which then causes damage to the plants foliage. Mind you, the same article describes how air blowers and half hourly visits by helicopters overhead can be used to reduce the damage caused by frosts!
I haven’t done any controlled experiments but the fruit trees and bushes have done well in the last few years. What I want to do now is find other plants that I could use under fruit trees that might produce a yield in other ways. I will follow this up in a later article.