I want to run a single zone from two different valves

I have two gardens, each one on a separate valve, and my wife just asked me to irrigate the potted plants on the deck. I don’t have enough wires in my controller cable going to my valve cluster or I would just put in another valve. Can I just tee into the two garden valve water outlets so when one valve comes on it waters its garden and the pots, and when the other valve comes on it waters its garden and the pots. The pots need roughly twice as much water as the gardens. Any problem with pressure coming back onto the backside of a valve when the other valve is open?