URBANA, Ill. – Growing asparagus is best reserved for patient people, as the first crop cannot be harvested for at least a year after planting. This frustrates many home gardeners, and is one factor that can make asparagus relatively expensive in grocery stores. Commercial growers must spend time and money to weed and maintain plots before they yield any asparagus, says University of Illinois Extension Educator Jennifer Nelson.
“Expect to harvest asparagus 1,095 days (three years) after planting from seed – not exactly encouraging, but it makes sense if you know how the asparagus plant grows,” Nelson says. “The first year, the plant develops a crown, or growing point, with an extensive root system. The second year, the crown begins to produce a fern-like shoot above ground. It isn’t until the third year that the characteristic asparagus spears emerge from the crown in the spring and early summer.”
Most people choose to plant one- or two-year-old asparagus plants, commonly called roots or crowns, and only have to wait a year or two before their first harvest.
“My husband and I only harvested during the first month that the spears appeared,” Nelson says. “Plus, we only picked some of them in order to let the plants produce abundant above-ground growth. As our asparagus bed has matured, we can harvest for roughly six to eight weeks each spring. Nothing from the store matches the taste of home grown asparagus!”
When growing asparagus at home, look for male hybrids such as Jersey Knight, Jersey King, and Jersey Giant. These were developed in New Jersey, the fourth largest producer of fresh asparagus in the United States. Not only do these male hybrids yield more, they show resistance to rust and fusarium, common fungal diseases in asparagus.
Asparagus grows best in well-drained, even sandy soil. Weed control is crucial to developing a good crop. Many myths circulate about applying table salt to asparagus plantings to control weeds. Although it is true that asparagus will tolerate higher salt levels in soil than most weeds, this is a poor weed management strategy. The excess salts inhibit water penetration into the soil, potentially stressing the asparagus plants. It is also very likely that excess salts will leach out of the asparagus bed and affect other plants.
Weeds can be controlled in an asparagus bed using a multi-faceted approach. Early in the season before asparagus shoots emerge, cultivate shallowly to eliminate weeds. Follow up with three to four inches of mulch. If desired, apply pre-emergent herbicides such as trifluralin (the active ingredient in Preen) or corn gluten meal (an organic alternative) at this time, as well. Pay special attention to avoid applying pre-emergent herbicides in garden areas where seeds will be planted, as these herbicides will prevent any seeds from germinating, not just weed seeds.
It is also possible to apply non-selective herbicides such as glyphosate to an asparagus bed before the shoots emerge, or after the last harvest, as long as all asparagus spears are removed, as glyphosate will potentially kill the asparagus if it makes contact with green portions of the plant. This method is particularly effective when perennial weeds are a problem. As with any type of herbicide use, Nelson cautions users to read and follow the label directions.
When choosing the placement of a new asparagus bed, Nelson suggests planting asparagus at the edge of the garden so the plants are not disturbed when tilling the garden in the spring. “A western exposure is the best place for asparagus. That way, the tall ferns that develop from the spears do not shade the rest of the vegetable plants during most of the day,” she says.
It is best to leave the fern-like growth intact until it turns brown in the fall. Like spring bulbs, the foliage of asparagus helps generate energy for the following year. Asparagus beetles are a common insect pest on the foliage, but they can be controlled per label directions with an insecticide specifically labeled for these beetles.
Plants should be fertilized each spring before shoots emerge with 20 to 25 pounds per 1,000 square feet of a balanced fertilizer, followed by another treatment after the last harvest.
Leaving some shoots in the ground will maintain quality over time. Nelson recommends that home growers leave a portion to develop ferns, which will fuel the next year’s harvest. A well-maintained bed will keep producing each year for 20 years or more.
Asparagus can be harvested either by cutting or snapping the shoots near the base. Cut shoots will need to be trimmed before cooking to remove the tough fibrous ends. Trimming is not necessary if shoots are harvested by the snapping method, since they will have broken where the tougher stem material began. To do this, grasp each spear and gently bend it until it naturally breaks.
Nelson is regularly asked where white asparagus comes from. She explains, “White asparagus is regular green asparagus that has had soil loosely mounded over the top as the spears emerge. The spears remain milky white without exposure to sunlight. It’s a lot more labor intensive than regular asparagus, so it’s more expensive in the store.”
For more information on growing asparagus at home, visit University of Illinois Extension’s “Watch Your Garden Grow” website at http://extension.illinois.edu/veggies/asparagus.cfm.