Asplenium loves it's soil to remain moist at all times, but not soggy. Water around the edge of the center rosette to avoid the water becoming stagnant in the center, which may cause rot.

Humidity may need to be improved if it becomes low and Asplenium is showing signs of being affected by dry air. You can improve the humidity by standing the plant in a humidity tray, a tray of peat moss or use an electronic humidifier.