Asparagus is a long-lived perennial which thrives in northern gardens. It is hardy, relatively free of pests and diseases, and provides plenty of tasty and nutritious spears early in the year when garden produce is especially valued.
Asparagus may be grown from seed or purchased as one or two-year-old crowns, depending on whether you have more time or money. The bed should be thoroughly dug and enriched with organic matter before planting in a sunny, sheltered location early in spring. Dig a trench about six inches deep, and place the crowns in one to one and a half feet apart, with rows three to four feet apart. Gradually cover the crowns with soil as the shoots grow upwards. Ferns will grow to about five feet, so don't let them overshadow other vegetables. Applying two inches of composted manure every other year should be sufficient fertilizing, but a high-nitrogen fertilizer (34-0-0) can be added after spear production is finished to encourage fern growth. Ferns should also be given about an inch of water a week while they are growing.
Begin harvesting spears when the plants are four years old, for about two to four weeks. In following years, harvest for four to eight weeks, or until the end of June, leaving enough ferns to mature to feed the roots for next year's crop. Plants will reach peak productivity at about ten years of age. Snap the spears off at ground level when they are six to eight inches tall, or cut them one or two inches below ground level, being careful not to damage emerging shoots. Asparagus crowns are very hardy, but the emerging shoots are tender and should be harvested or covered if a frost is likely.
'Mary Washington' is a common cultivar, but 'Viking' has higher yields, and the 'Jersey' series are all-male, which means they will likely be longer-lived and more productive, and the chore of weeding out volunteers is avoided. (The berries produced on female plants are not edible.) All these varieties are resistant to rust.
Asparagus is best when very fresh, but there is no need to boil a pot of water at the end of the row on your camp stove so the spears can be cooked within seconds of being picked, as one story has it. Harvest stalks early in the morning, when they are sweetest and most tender, and refrigerate immediately, or they may become dryer and tougher. To freeze, blanch slender spears for two minutes, medium and large spears for three to four minutes, then cool and freeze for up to a year.