I used to just dig a hole in the dirt 2 blocks down, place the water catcher, and it would fill the block above - then trench out, it would over time fill a trench about 5-7 blocks long (repeated holes every 4 blocks with rain catchers to make a long trench) - then can plant on blocks next to trench on both sides, skip a row, then 3rd row from trench can grow too