Asparagus is high in vitamin C and folate. Once established, plants supply spears for eight to ten decades. Asparagus grows in USDA hardiness zones 2 to 11, though it prefers a temperate climate. Gardeners in warm climates should choose varieties especially bred for their place because the temperature affects asparagus development patterns.
Asparagus is a perennial plant, and the spears are the new shoots the plant produces every year. To produce healthy flames, plants require a period of dormancy, which occurs when the plant is very cold or experiences drought. Varieties appropriate for warmer climates include UC157, De Paoli, Apollo and Atlas. These respond to drought dormancy. UC157 and De Paoli are commonly grown in California.
Asparagus plants are sensitive to changes in temperature. Plants need temperatures to be between 75 to 85 degrees Fahrenheit throughout the daytime and 60 to 70 degrees Fahrenheit in the night. Asparagus plants start to produce new shoots when soil temperatures rise above 50 degrees Fahrenheit. At optimum daytime temperatures, asparagus spears grow between 3 and 6 inches every day. Growth rate increases as the temperature rises.
Extreme Temperature Effects
When temperatures get greater than 85 degrees Fahrenheit or lower than 55 Fahrenheit, root and shoot development slow down. High temperatures cause shoots to open prematurely into feathery fronds, which are inferior quality, or grow into misshapen forms. High temperatures also cause narrow, tapered spears with loose heads. Freezing temperatures cause emerging flames to become discolored; this is referred to as frosting.
You can grow asparagus from seed, though it’s slow to germinate and dependent on soil temperature. At a temperature of 50 degrees Fahrenheit, seeds take about 53 days to germinate. Higher temperatures slow germination rates also. The optimum soil temperature for fast germination is 77 degrees Fahrenheit, when seed germinates in about 10 days. Soak seeds in water for 48 hours before sowing to increase germination speed.