Ah, 2 Ficus and an elm. The balcony, even though it faces north is a far better place for your trees than a windowsill for the summer. Actually, you Chinese elm might be happiest spending winter on your balcony, central Maryland is not that cold, the Chinese elm would really like a cold, totally dormant rest better than being forced to grow all winter on a windowsill.
One of the benefits of the balcony, is the daily temperature swings. Trees like to warm up during the day, high 70's through the middle 80's are ideal for photosynthesis, and they like to cool off at night. This happens without human intervention when trees are grown outdoors. Humidity will be more favorable outdoors on the balcony.