An asparagus bed provides you with fresh asparagus spears for 15 years or longer. These perennial vegetables are actually the early shoots of the asparagus fern, a tall, spreading plant that reaches its full size in late summer when you are done with the yearly harvest. During the first part of spring and summer the asparagus bed is unattractive as you frequently harvest the spears and before they begin foliage production. Improve the look of the bed by planting annual flowers with the asparagus plants.
Plant asparagus in the rear of the bed. Space the crowns 18 inches apart and plant them 8 inches deep. Multiple rows can be planted 4 feet apart, but a single row usually suffices if you are growing them with flowers.
Sow annual seeds in spring at the planting date recommended on the seed packet. Choose cool-weather annuals such as pansies or petunia that slow or stop production once the temperatures warm in summer. Plant the seeds at the depth recommended on the seed packet, usually to a depth twice their diameter, and place them at least 3 feet away from the asparagus plants.
Deadhead the annuals as soon as the flowers begin to wither so they do not self-seed in the garden, as volunteer seedlings the following spring may become weeds in the asparagus section of the flower bed. Pinch off the spent flowers and any forming seed heads and dispose of them.
Harvest the asparagus spears as usual throughout early summer. Cut them off at the soil level when the spears are about 6 to 8 inches tall and as thick as your finger. Continue to harvest the spears until July 1.
Allow the asparagus to develop into ferns in July. Asparagus requires foliage growth in later summer so the roots can replenish the nutrients needed for the following year.
Maintain the flowers for as long as they are blooming, removing spent flowers and watering them when you water the asparagus bed. The asparagus ferns shade and cool the soil, allowing cool-weather annuals to bloom longer, but they may begin dying from over-shading or too much heat in August regardless.