Morning glory is a vigorous annual vine that produces trumpet-shaped flowers that come in an array of colors including blue, violet, pink and white. Once established, morning glory vines can tolerate a dip in the temperature, but seeds need a warm, moist environment to properly germinate. The flowers on mature vines are temperature-sensitive, too. As the name suggests, they open in the cool morning hours but close during the heat of the day.
Morning glory seeds need a minimum soil temperature of 65 to 70 degrees Fahrenheit to properly germinate. Sow morning glory seeds outdoors when the soil reaches that temperature range in your area in the spring. Get a jump on the spring planting season by starting morning glory seeds indoors in peat pots four weeks before the last frost in your area. Soften the hard outer coating of the seeds by soaking them in tepid water for 24 to 48 hours prior to planting. Plant three to four seeds in each pot, and cover with 1/4 inch of soil. Keep the soil moist but not soaking wet. Seeds germinate in about seven days. When the weather warms, plant the entire peat pot outdoors; morning glory does not tolerate transplanting well.
Mature morning glory vines require temperatures that stay above 45 degrees F to continue to bloom. They will endure a light frost, but a hard frost and freezing temperatures will kill the vines. To thrive, morning glory requires full sun or light shade. Plant it near a building where the air temperature remains moderate for a longer period of time to extend the plant's longevity. Depending on the variety, some morning glory flowers open at morning temperatures in the 50s F, while others require temperatures in the 60s. The temperatures that trigger flower closing vary as well; some close up when the temperature reaches around 80 degrees F, but others are more heat-tolerant and will remain open when the temperature climbs to more than 90 degrees.