I plant in several troughs and large galvanized tubs. Instead of drilling holes in the bottom I put holes in the side of the containers near the bottom. I live in an area where summers are very hot and dry. This half to one-inch area in the bottom of the trough acts as a 'tray' does under any pot to catch water and allow the plants roots to absorb it before it quickly drains away. The plants that grow in the ones with side drainage outgrow the ones with bottom drainage.
Note: Holes may be put in the side of these large metal containers with hammer and a very large nail or spike much easier than in the bottom.
