My apples and pears have always had other herbaceous plants near them. Say about a foot away so as not to disturb the roots. One has a Spirea pretty close to it. Bulbs in season as well.

Companion planting Digitalis reputedly enhances the keeping qualityof apples. I have some of themand autumn flowering chryanthemums under my apple trees. I did keep the soil free for the first few years to allow them to settle in. Apple tree roots are fairly close to the surface so take care when planting.