Asparagus should be well established after planting before any spears are harvested. Do not harvest asparagus for the first two years after planting. In the third and following years, asparagus can be harvested until early to mid-June in Iowa. If harvest begins before April 15 because of warm, spring weather, stop harvesting by early June. Continue harvesting until mid-June if the first harvest occurs after April 15. Ending the harvest season in early to mid-June allows the plants to develop strong, healthy top growth and to store adequate food reserves in their crowns for next year’s production.
For maximum yield, spears should be 6 to 8 inches long when harvested. Tender spears are sensitive to frost damage; so in early spring it‘s advisable to cut the spears prior to the 8-inch height. Harvest by cutting or snapping the spears. Use a sharp knife to cut the spears at the soil surface. Cutting below the soil surface may damage spears that have not yet emerged. Breaking or snapping is also a satisfactory method for harvesting asparagus. Break or snap the spears slightly above the ground. The harvest frequency depends on temperature and moisture conditions. In warm weather, it may be necessary to harvest every day. In cooler periods, harvesting may be done at 2- to 3-day intervals. “Clean cutting” (the removal of all spears) is desirable during the entire harvest season. Allowing some of the spears to continue to grow and produce fern-type growth inhibits the development of new spears.
Asparagus deteriorates rapidly after harvest. Store asparagus spears in the refrigerator at a temperature of 32 to 35 degrees Fahrenheit in order to retard fiber development.