Hollyhocks can typically grow in temperatures ranging from 55ºF to 90º F. If you live in a climate with near-freezing or freezing winter temperatures, mulch the soil around your hollyhocks to insulate dormant roots. Meanwhile, if summer temperatures are consistently above 90º F, water your hollyhocks frequently to ensure their soil stays moist, and position them where they will have shade from afternoon sun. Hollyhocks do not like humidity, which can cause diseases.