Asparagus is one of the first vegetables to peer through the cool soil in spring, and what a welcome sight! The heavy snows this past winter provided excellent moisture and insulation for the plants, so the crop is off to a great start.
Precisely how to harvest is the subject of some debate among asparagus gardeners. Some prefer to harvest only the very young spear tips. This ensures that only the tender portion of the spear is harvested, but yields are smaller.
Most gardeners allow the spears to reach 5-8 inches in length and then cut or snap at, or just below, the soil line. The very bottom of the spear will likely be a bit tough and fibrous, so re-cutting the bottoms before cooking will keep just the tender spears. If you use a knife to harvest, you may injure nearby spears that have not yet emerged. So many gardeners prefer to snap them off by hand.
Newly planted asparagus beds may produce a few harvestable spears the first year, depending on the quality of the planting stock, but you don’t want to overharvest, as this will deplete the plants resources and result in a smaller harvest next year. Make two or three cuttings and then allow the subsequent spears to develop into foliage. Established plantings can be harvested for 6-8 weeks. Be sure to check the bed 3-4 times each week during harvest season, as the spears can quickly go from not quite ready to a bit too mature very quickly!
Quit harvesting when the majority of the spears are spindly (less than 3/8 inch in diameter). The spears will become feathery, fern-like shrubs that will rebuild food reserves for the following year. Fertilizer applied at this time will encourage foliage growth. For most established asparagus beds, nitrogen will be the primary nutrient needed; phosphorus and potassium need only be applied if a soil test indicates they are needed. The exact amount of fertilizer to apply will depend on the specific product you are using. If using composted manure, apply 1-2 inches over the bed. If using ammonium nitrate, apply about 1/2 cup per 10 feet of row.
Allow the foliage to stand at least until it dies back in autumn. Then you can either cut it back to the ground when cleaning up the garden, or leave the brown foliage to stand overwinter to collect leaves, snow and other insulation.