Overwatering is the leading cause of succulent plant death, and it could lead to a dead air plant as well. This plant can grow up to 2 feet tall and 2 feet wide in sunny and warm climates. You will need to position your String of Hearts in a west or south-facing window. However, it may be possible to keep them directly in an east or north-facing window. Lithops don’t need much fertilizer but you can still give them a bit every few weeks to help them grow strong and healthy.