They work great for gardens! Have a friend that raises cattle and gave us all we wanted. Used them for my maters etc... Drill a few drain holes and you’re good to go. Took this pic before things got growing.
This is what we use. 2 pieces of French drain in the bottom flat, 1 drain hole 5in off the bottom. 1 inch pvc pipe to water through to the bottom. Fill with dirt compost and grow! Roots chase down to the water. Only fill through 1” pvc.