My grandfather also advocated planting by the phases of the moon - as long as good gardening practices otherwise permitted. He might lament the soil being too wet to work to plant potatoes at the new moon, and fret about what it might mean for yields if soil conditions and moon phases didn't agree with one another, but he wasn't about to ruin the tilth of the soil by working it when too wet.

I suspect the same is true for any experienced gardener, even those who subscribe to planting by moon phases. I've never known a good gardener to eschew planting when the soil and season are right but the moon is not.

If both moon phase and soil conditions are right, there is no harm done in planting by moon phase, and in terms of planning and hopeful expectation, thinking about upcoming moon phases probably psychologically prepares the farmer or gardener for the approaching season. I haven't really looked at this and may be wrong, but I am of the impression that most crops that are associated with planting by the phases of the moon are crops that are usually planted from late winter to early or mid-early spring, when soil and climate conditions are most capricious and iffy. Gardening is part planning and part stoicism. In the winter planning phase, thinking about all the crops that need to get sown or set in the ground in a relatively brief window of time, usually a climatological window of 4-6 weeks, thinking in terms of moon phases can give one the hope of a schedule that the climatological and soil conditions will permit.

And mother nature can and usually will throw a few curve balls.