With apple trees I grow most veg, and strawberries too, right up to their trunks, though not carrot and parsnip as they would be hard to remove without hurting tree roots. Potatoes is possible if you grow themn in surface compost, with tubers develkoping in that, and first earlies will grow to maturity before trees are themselves growing too much. Winter squash trail happily under apple trees.
My espalier tree rows are at the centre of three foot (one metre) beds where I grow the veg. See here
and there is 4.5 metres between each row of apple trees.
Sorry it is tricky to photograph in a clear way.