I've spent a few days positioning my gardens just right, so I can have all 4, 12 plot gardens for my couch potatoes under one column. I've read that the gardening spells hit 60+ plots, however, my spells are only effecting 2 layers of plots, not the top 2 from the ground, or the bottom 2 from the floating gnome... Is this normal that only 2 levels can be gardened at a time??
It depends how closely the levels are spaced. In my experience if the levels are stacked 1 crate height apart, large area spells will cover 1 level up and down from the level aimed at, so 3 levels is normal. For CP I stack in a circular pattern with levels much closer that 1 crate. You need to be creative to be able to fit 69 large plots into a single large spell.
Just as an FYI. The garden spells have a vertical effect of 1½ layers - or crates. If you place a wooden crate on the low square table (low square table is ½ of the height of a dark wood crate), you will be able to place an object 1½ 'layers' off the ground. In this way, you can actually create a garden that is 4 layers high and still hit all the plants. The item you place at 1½ must be floated in the middle of your garden spell ring. I use the Tropical Garden Gnome since most plants like this item. Once the gnome is placed, I simply aim/cast the spell right on the gnome!
This happened to me. I floated my likes too high and when aiming it did not cover the bottom level. Just do what you can to get through this round and then float something haflway up. As was said, the spell will cover 1 1/2 levels up and down.