Geranium is the common name given to a variety of plants in the family Geraniaceae. Geraniums are a favorite ornamental flowering plant grown in sunny locations both indoors and outdoors. According to the North Carolina State University, geraniums are relatively easy to grow from stem cuttings and exhibit hearty growth in the appropriate environmental conditions. Temperatures for geranium growing are typical of temperate summer climates but vary depending on the growing location.
Indoor geraniums grow best with stable temperatures and lots of natural light. According to the Clemson University, geraniums grow best with daytime indoor temperatures between 65 to 70 degrees F, with nighttime temperatures around 55 degrees F. Indoor growing is common during the winter months because the plant cannot survive multiple frosts and low temperatures. Geraniums require plenty of natural or artificial light yearlong. The Clemson University recommends using a 40 watt fluorescent bulb for 16 hours per day if natural light is not present. Indoor geraniums grow best in stable temperatures, rather than locations that vary from cold to hot or areas that are drafty.
According to the University of Massachusetts, geraniums can grow in temperatures ranging from 45 to 80 degrees F but grow best with temperatures ranging from 60 to 75 degrees F. Outdoor growth of geraniums depends both on daytime and nighttime temperatures. Temperate climates help the plant with photosynthesis and respiration, whereas cooler temperatures reduce these processes. According to the University of Massachusetts, geraniums grow best in outdoor temperatures that range from 70 to 75 degrees F during the day and 60 to 65 degrees F during the night. Temperatures above 80 degrees F can result in plant stress, causing decreased growth and a loss of color. However, different geranium varieties respond differently to varying outdoor temperatures, which determine its growth potential with extreme temperatures on the high and low ends of the spectrum.
Geraniums are common as annuals for most growers; however, they are sometimes overwintered and survive from year to year. According to the North Carolina State University, overwintered geraniums can survive indoors with temperate climates and plenty of sunlight. They can also survive in a moist basement with 80 percent humidity and temperatures ranging between 35 to 45 degrees F. However, avoid lower temperatures because the plant can freeze and die. Another concern with overwintering is that the plant can carry diseases from year to year and can transmit them to other indoor geranium plants