Common geraniums, known botanically as Pelargonium sp., are common summer annuals prized for their clusters of blooms and their velvety green, trailing foliage. According to the University of Massachusetts at Amherst, the effect of temperature on geranium growth and performance is substantial, but varies by species — of which there are more than 14 — according to the U.S. Department of Agriculture. Treating geraniums as tender warm-season plants and observing general temperature guidelines will ensure peak rate of growth and flowering capacity.
- Moderately Easy
- Refrain from locating your geranium plants where they will be exposed to ambient temperatures at or below 50 degrees Fahrenheit for any longer than 12 hours. At 50 F, the growth processes are nearly halted and the older leaves will become permanently discolored.
- Grow your geraniums where low nighttime ambient temperatures remain at or above 60 F. At 55 F the plant will survive, but growth is anemic and flowering delayed.
- Prevent your geraniums from exposure to temperatures below 45 F, as this is when more serious tissue damage and plant death begin to occur for some species and cultivars.
Tips & Warnings
In addition to cold temperature sensitivities, geraniums do not perform well under excess heat either. Choose a growing location where ambient daily temperatures stay at 80 degrees or below to prevent performance-impacting heat stress and leaf burn.