If you have planted asparagus in recent years there are a few guidelines for harvesting which can help ensure the future success and health of the planting. Over-harvesting new and mature plantings can weaken plants, and reduce next season's crop. New plantings need several years to develop mature, underground crowns that can support sustained harvests.
Asparagus spears start to emerge when soil temperatures reach about 50F. After emergence, growth is dependent on air temperatures. Thus, as temperatures warm, picking frequency increases. In the early season you may pick once every 3 to 5 days, at peak season once, possibly twice a day.
In a new bed, avoid harvesting the year of planting. This allows time for proper early grow and development. Recent research has shown that removing a few of the earliest large spears in the second year after planting may promote growth. This should only be done when first year growth was vigorous. By the third season a limited harvest period of two to three weeks is possible. Choose only those spears which are larger than a pencil, and wait until they are 7 to 10 inches long. Spears should be snapped at ground level or cut just below the surface. In the fourth growing season, harvest for about 4 weeks, and in successive years 6 to 8 weeks or until emerging spears start reducing in size (pencil diameter).
For all plantings, a key goal is to encourage good foliage or "fern" growth that builds the crown buds for next year's crop. Thus it is important not to neglect asparagus foliage during the summer after harvest, and to keep it healthy over the growing season. Be sure not to mow or cut it back until after first fall frost. Rarely will asparagus need extra water because of its' deep rooting habit, however it will respond to fertilizer. Fertilize plantings before first spears emerge using 1 to 2 lbs per 100 square feet of 10-10-10 or equivalent fertilizer. Some plantings, depending on soil type, may respond to dividing this amount between before and just after the harvest period.
Remember to control weeds that compete with asparagus. This can be done using garden mulch, or by the use of Preen™, a pre-emergence garden herbicide registered for asparagus. Do not salt asparagus beds to control weeds. Often used in the past as a means to control weeds in asparagus (which is salt tolerant), salt can render the soil unsuitable for any other crops in the future.
When present, control diseases and insects, keeping an eye out for asparagus rust and other stem diseases and the asparagus beetle which can damage foliage. Though usually not severe, these problems can be managed with an appropriately timed fungicide or insecticide.
Information about asparagus growing and other garden crops can be found in the University of Illinois publication entitled "Vegetable Gardening in the Midwest" Circular 1331, available at your local County Extension office or visit the University of Illinois website "Watch Your Garden Grow" at http://www.urbanext.uiuc.edu/veggies/.
Source: Anthony Bratsch, Extension Educator, Horticulture, firstname.lastname@example.org
Pull date: July 24, 2008