Citronella plants won't do much. Use the oil.

Not very effective, honestly. But if you want the scent without a candle flame, your best bet is an electric diffuser or a spray.

The live plant people sell at garden centers? Almost useless. You have to crush the leaves to release any oil, and even then it’s weak. The compound mosquitoes dislike is citronellal, and it’s concentrated in the oil, not floating around the plant.

So buy 100% citronella essential oil and put it in a fan diffuser. The constant airflow spreads the smell better than a candle. You can also mix a few drops with water in a spray bottle and mist around the patio furniture, but it evaporates within an hour. Reapply.

FWIW, citronella is a mild repellent at best. You’d be better off with a box fan blowing across the seating area or a Ther