Master Gardener Onen Markuson: Keys to growing asparagus
Gardening is always at least a little risky, and you always have to be at least a little patient to see the rewards. A few years ago, my dear wife decided she wanted to grow some asparagus, and being the bargain hunter that she is, found an out of date package of a “Mary Washington” variety of asparagus seeds on sale for a dime.
I was skeptical these would amount to anything as the seeds were out of date, but humored her, and let her use our new heated seed starting kit on this “long shot.” She planted all 30 six “cells” of a simple seed starter system with two seeds in each cell, put in some water, covered the kit and turned on the heat pad. Much to my surprise, every one of the “cells” had at least one asparagus seedling. (A “reduced risk” option, with a better chance at a successful crop, and with quicker results can be had with the purchase of 1-year-old asparagus crowns.)
In the late spring – after the frost – we transplanted the asparagus seedlings into its “nursery” bed spot in our garden. We planted them about four inches apart. Except for weeding and watering, we left them alone until the next spring. No asparagus growth should be harvested the first three years when planting from seeds, as the plants need their energy to produce a good root system.
In the very early spring after the first year of growth, there is quite a bit of preparation needed for the main asparagus bed before transplanting your seedlings or purchased crowns. This transplanting requires a trench, which is at least one foot wide and one foot deep. At the base of your trench, you should put at least six inches of rich soil, well-composted manure and/or good compost. Plant each crown 12 to 18 inches apart on top of a small, rounded mound of the rich soil. Add two or three additional inches of rich soil on top of the crowns and water. After the crowns have broken through that layer, add another two or three inches of soil and keep doing this until the soil reaches about the level of the surrounding garden. It is important that the crowns be planted at a good depth, so they are protected from winterkill and from freeze damage if they emerge too early. You can plant some deeper for a slightly later second harvest.
Asparagus is a heavy “feeder,” and annual applications of fertilizer should help your crop. The fertilizer should be worked into the soil, and can be either well-rotted manure, compost, or a synthetic fertilizer with a low phosphorus level (second number). Keep weeded and mulch mid-season to control weeds and retain moisture.
Wait until the third or fourth year of growth before harvesting, as asparagus plants need to develop a very substantial root storage system. Well-developed asparagus roots can go down over six feet. Your patience can lead to 15 years of harvesting this one bed of asparagus.
Cindy Tong of University of Minnesota Extension recommends growing one of the all-male hybrids like Jersey Giant for greatest productivity. They may be more susceptible to winter kills at 30-below zero, but proper planting and heavy mulching after the ground freezes should do the trick. Seek horticultural information on the University of Minnesota Extension website at www.extension.umn.edu/gardeninfo, where Cindy has a specific article on this topic.
Master Gardeners will again be answering your gardening questions via a voice-mail service. Call 444-7916, leaving your phone number, name and the nature of your question. A master gardener will give you a call to speak with you personally. If there is a best time to reach you, mention that as well.