Asparagus is has been grown for at least two millennia. It is not susceptible to many disease problems. It’s a good source of vitamin A and also has good amounts of calcium, folic acid and Vitamin C. A cool season perennial which can live for decades, asparagus does require some work to get started, but unlike other vegetables, it will keep producing for many many years. It will need regular watering in early years, but requires much less work than most other vegetables once it becomes established. Besides, those little shoots peeping out each year are a great harbinger that spring has arrived…and, once you’ve tasted freshly-picked asparagus, you’ll never go back to the store-bought stuff!
Asparagus has a large root system with feeder roots and rhizomes that develop into spears and storage roots. Roots can grow very deep (at least 6′) and wide. Warning: asparagus will not tolerate wet feet - if you have an area with a high water table, do not plant them there. Asparagus prefers a soil pH of 6.5-7.5, and doesn’t do well if pH is less than 6.0.
Each planting row should be a furrow at least 5-6 inches deep and as wide; keep rows about 5 feet apart. Loosen soil as deeply as you can from the bottom of the furrow. If the soil removed from the furrow was a sandy loam, it can be mounded for filling in as the plants grow. If you have a fine clay or silt soil, remove it and use it in a low spot elsewhere (or use a raised bed). Mix several inches of a good planting mix in the bottom of the furrow. If lime is needed to adjust soil pH, add that at this time.
Next, make a small mound so the asparagus crown will be on top and the roots spread around it. Plant the crowns/roots 4-6 inches deep (shallower in clay soils). Cover them 3 inches with half organic and half sandy loam mix (or use a good planting mix if you have clay soil), then wet the entire row. When the plants are several inches tall, add another layer of the above mix (avoid covering the foliage - it’s better to fill too slowly than too quickly) until the furrow is full. Water weekly if it doesn’t rain. (Stop watering in early autumn to encourage dormancy.)
Pick no asparagus shoots the first year; allow the foliage to grow, yellow and die on its own. This creates the food for the roots. Mulch in autumn with straw, compost or strawy manure to reduce heaving from freeze-thaw cycles and to delay early spring emergence of spears. During early spring of each year, remove the dead foliage and any overwintering weeds. (Don’t cut the fern down in the fall - the dead fern will catch moisture and snow in the winter and will keep the soil temperature about 5 degrees colder than the temperature of bare soil. This colder soil temperature will delay early emergence of spears in the spring, which could then be killed by a late spring frost.) Also broadcast lime, if it is needed to maintain the proper soil pH. At the same time, spread 2 to 3 pounds of 5-10-10 fertilizer per 100 square feet and rake both fertilizer and lime into the upper 1-2 inches of soil.
The second year, pick sparingly only those stalks as big as your finger. Keep watering, fertilizing, and mulching with manure and compost.
The third year is the year to really begin harvesting. The 2-4-8 week sequence is a good rule: pick for two weeks the third year, four weeks the fourth year, and eight weeks from then on. To harvest - when the stalks are at least 7 inches high, just snap where they begin to be tender and enjoy. (If you use a knife or clippers, you risk accidentally cutting immature spears and also spreading disease between plants.) Stop harvesting when a majority of the shoots are smaller in diameter than a pencil.
Good companion plants for asparagus are tomato, parsley, and basil. By the way, just a bit of trivia - asparagus is one of a fairly small number of salt-tolerant vegetables. It used to be traditional to sow salt on asparagus beds to control weeds. (We wouldn’t recommend that in most places, as the salt might run off and kill less tolerant plants.)