Are you trying to make your farm pretty, or do you just not want to plant your crops too close together?

IMO, the easiest way to ensure that plants are not too crowded is to not plant them too close together. The best way to ensure that is to give them plenty of space. That may sound like I'm stating the obvious, and I am, but many still don't get it.

Valheim is a big world. You don't need to optimize your planting space. Just make your farm a bit bigger, to allow you to space out your plants a bit more. You can then just plop them in the ground and not worry that they're too close. It goes much faster and is much less of a chore.