Light:
Asparagus plants grow best in full sun. Without enough daily sunlight, you will wind up with thin spears and weak plants that are prone to problems.
Soil:
For a long-lived perennial like asparagus, it pays to take the time to improve your soil before you plant it. Work in plenty of organic matter and make sure the soil pH is in the neutral 6.5 to 7.0 range. Also get rid of any weeds and large stones in the area before planting.
Water:
Asparagus needs regular watering, especially while young; give it 1 to 2 inches of water per week during its first two growing seasons; give older plants about 1 inch per week. If you give them a good start when you first plant them, and you’ll have fewer problems in future years. Consider adding drip irrigation or a soaker hose to the asparagus bed.
Temperature and Humidity:
During the growing season, asparagus prefers a temperature of 70 to 85 degrees Fahrenheit during the day and 60 to 70 degrees at night. In the spring, it will begin to grow shoots when the soil temperature reaches 50 degrees. Any frost after the shoots start growing will cause discoloration. You may see slow growth with temperatures above 85 or below 55 degrees.
Fertilizer:
When preparing your asparagus bed, add compost and an all-purpose organic fertilizer to the trench, as well as rock phosphate, a natural mineral powder that promotes root growth.