Asparagus is an attractive and delicious perennial vegetable that can thrive in the home garden for 25 years or more. Low in calories and high in flavor, a serving of four asparagus spears (60 grams) contains 10 calories, 1 gram of protein, 2 grams carbohydrates, and only traces of fat. Asparagus is high in vitamin A and riboflavin and a very good source of thiamin.
Asparagus needs a long growing season and sunny days for maximum photosynthesis. It grows best in deep, well-drained soils. Soil pH should be maintained between 6.5 and 6.8. Medium soil fertility is best to provide a balance between top growth and root growth, but the plant needs relatively high amounts of phosphorous and potassium levels for maximum spear production.
Before planting, broadcast and turn under 7 pounds of 5-10-10 fertilizer per 100 square feet. If lime is needed, turn it under along with the fertilizer. In the Northeast, the recommended varieties for home use include Rutgers' Beacon, Rutgers' Synthetic, Jersey Giant, and Jersey Centennial.
Plant healthy, 1-year-old crowns with the buds up in the bottom of a 10-inch deep furrow; cover with 1 inch of soil. Crowns should be 12 inches apart within the row, with 36 inches between rows. As the asparagus grows, carefully fill the furrow with soil but avoid covering any foliage; furrows should be filled in by the end of the first growing season. In July of the planting year, side-dress the plants with 6 pounds of 5-10-10 fertilizer per 100 feet of row. Spread the fertilizer on either side of the asparagus and cultivate lightly into the soil. Mulch in late October 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 asparagus foliage and overwintering weeds. Also, broadcast lime as 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. In July, side-dress plants with another 2 pounds of 5-10-10 fertilizer per 100 feet of row.
It is very important that asparagus plants have two full growing seasons before their spears are picked. The 2-4-8 week sequence is a good general rule for harvesting: pick for two weeks the third year the plants are in the garden, four weeks the fourth year, and eight weeks the fifth and following years. When harvesting merely snap off the upper green, tender portion of all tight heads 7 to 10 inches long. Harvest all spears that come up during the harvest season. One 40-foot row of 5-year-old asparagus will yield approximately 10 to 25 pounds of spears during the average season.
Both the beetle and the grub feed on young spears, ferns and stems of the plant. Beetles are particularly a problem when they feed on the young shoots in the early spring. If you do not see the beetle and notice plant damage, check for shiny black specks on the spear tips. The adult beetle is approximately 1/4-inch in length and the body is wider then the head. The adult beetle can be identified by its dark orange body with black spots. The grub is orange with a humpbacked shape. The best time to control the beetle and the grub is in the early fall, before the first frost. If you use mulch around your plants, pull it away from the base of plants in the early fall since this is where the grubs overwinter.