Although there is variation in care requirements across hollyhock species, most are known for being adaptable and relatively cold-hardy plants that can be grown in many U.S. regions. Pick sites sheltered from the wind to prevent these tall plants from flopping and space individual plants far enough apart to promote good air circulation—most hollyhocks are susceptible to the moisture-loving fungal disease rust. Positioning them anywhere from 18 to 24 inches apart is best.