Spatial Relations

I am not good at eyeballing distances. In fact, I am often quite wrong. That's why, whenever I plant anything, I use a ruler to measure how deep I have dug my hole.

The number one reason trees fail is because they were planted improperly. I think the same probably holds true for flowers, bulbs and vegetables. It is not difficult to determine how deep to plant a particular specimen--just read the label that comes with your seeds.

Of course, their is some margin of error, but, in general, planting depth should be as close to that recommended as possible.

Why?

Different seeds have different needs. Parsley seeds, for instance, germinate in the dark. They also risk drying out easily, so it makes sense to plant them a little deeper than, say, lettuce seeds which need light to germinate.

Photo From herbgarding.com
Parsley seeds need lots of moisture and complete darkness to germinate,
so they should be planted deeper into the soil than other seeds.