Light: Grey Star Calathea plants prefer indirect sunlight.Direct sunlight in the morning and afternoons is okay as the light is less harsh. If your room has a window you will be fine, although they grow faster the brighter the room is.
Water: They prefer to dry out between waterings. Press your finger about an inch into the soil and if it is damp, do not water it. If it is dry it is time to water. In the summer you will water twice as much as the winter waterings.
Soil:Well-draining potting mix will let it thrive.
Humidity: The average humidity in a house is great
