Apple and Comfrey
beneficial
Why this pairing
Comfrey accumulates potassium and phosphorus, providing a chop-and-drop mulch beneath fruit trees.
Practical considerations
Comfrey planted around an apple tree is one of the most effective low-input combinations in temperate orchards. Comfrey's deep taproot mines potassium, phosphorus, and trace minerals from subsoil and brings them up into rapidly growing leaves. Cut the leaves three or four times per season and let them rot in place under the apple tree as a chop-and-drop mulch. The result is steady nutrient cycling without any external fertilizer.
Plant Bocking 14 cultivar (sterile, doesn't spread by seed) in a ring at roughly the dripline of a young apple. Two or three plants per tree is enough; comfrey gets large. The plants out-compete grass and most weeds within a season, which simplifies orchard floor management. They also attract bumblebees during apple bloom.
The one caveat: comfrey is permanent. Once established, it's nearly impossible to remove. Don't plant it where you might want to do something else later. For an apple tree planted with a 30 to 50 year horizon, that's not a problem.