Trying an experiment this year. Garlic planted quite close together (10cm or so) and then onion sets placed between the rows at similar spacing. In theory the leaves will come up between the bulbs and the roots shouldn't interfere as they're at different depths but maybe it will be a disaster of pea-sized bulbs, we'll have to see I guess. The leaves will definitely interfere a bit, but since they're so long and thin I'm hoping it won't matter too much.
Trying an experiment this year. Garlic planted quite close together (10cm or so) and then onion sets placed between the rows at similar spacing. In theory the leaves will come up between the bulbs and the roots shouldn't interfere as they're at different depths but maybe it will be a disaster of pea-sized bulbs, we'll have to see I guess. The leaves will definitely interfere a bit, but since they're so long and thin I'm hoping it won't matter too much.