Will this be strong enough?

Wondering if this is going to fall apart once I fill it with dirt for a vegetable garden. Dimensions are roughly 2’x2’x8’. All pieces are 2x4 pine. The two vertical pieces at each corner are joined with 2 pocket hole screws 1/3 of the way in from the top/bottom. Will that join hold the weight of the dirt or do I need to add something more here? Also will the 8’ length be strong enough or am I likely to get some bowing?