Allow asparagus to grow without harvesting the year it is planted. In the second year, harvest spears that are 1/2-inch in diameter, but only for two weeks. Cut or break off 7- to 9-inch-long spears with tightly closed tips. In subsequent years, harvest for five to eight weeks, then allow the shoots to develop into ferny growth to build up the roots for the following year's crop.
HOW TO PLANT ASPARAGUS High in nutrition, asparagus is a good source of vitamins A and C as well as protein, calcium, folic acid and iron. Once established, this perennial vegetable plant produces tender asparagus spears every spring for 12 to 25 years. http://www.wikihow.com/Plant-Asparagus