Overwatering is the most common cause of succulent plant deaths. It could also lead to dead air plants. In warm, sunny areas, the plant can reach two feet in height. With a south or west-facing window, you'll likely need to place your succulent a few feet away, but you may be able to keep your String of Hearts directly in a north or east-facing window. Lithops don't need a lot of fertilizer, but you can give them a little bit every few months to help them grow healthy and strong.