Asparagus is a very hardy, cool-season perennial vegetable, which can produce a spring harvest for 10-20 years! Therefore, it must be planted in a “dedicated bed”. It can be grown from seed, but most often is grown from 1-2 year old “crowns” (rhizomes), which is offered in January.
For 6 crowns, you will need a dedicated area measuring 6’ wide x 6’ long.
For 13 crowns, you will need a dedicated area measuring 6’ wide x 10’ long.
Crowns are dormant and must be planted within one week; you may keep them in the refrigerator, so they don’t break dormancy, until you can plant out.
Asparagus requires rich, fertile, well-drained soil, with a pH of 7.0 – 7.2.
Mix in lots of compost. If gophers are a problem for you, install wire barriers down in the bed before planting. Be sure the bed is as weed-free as possible. They prefer full sun.
Be sure the soil is at least 50 degrees. Dig a trench 12-15” deep (roughly twice the length of the roots), and allow 3-4’ between rows. Mound up soil inside the trench to create a cone 6” tall; cones should be 1’ apart. If you are trenching down into regular soil, prepare the bed by the “double dig” method, adding in compost to assure a well-draining soil.
Over each cone, drape the roots of one asparagus crown. Begin filling the trench with soil, up to just 1” above the crowns, to start. Firm the plants in well. As the plants grow and shoots emerge, begin covering the crowns with more soil until the trench becomes level with the soil surface. Water well each time.
Asparagus takes a few years to fully mature. Do not harvest any shoots the first year; after they emerge, let them leaf out so the foliage can nourish the growing roots and rhizome for future production. Remember that good things come to those who wait!
You can begin to harvest lightly the shoots in the second year for about a month. The fleshy roots still need to develop and support perennial growth in future seasons. Plants that are harvested too much, too soon will become spindly and weak, and perhaps not recover. To harvest, simply cut or snap the spears 1-2” below the soil and at least 2” above the crown.
Subsequent harvests generally last for 8-12 weeks. Be sure to harvest daily during the season; either use or refrigerate immediately in a plastic bag. 6-8” is the optimum size. Don’t leave them to become tall and woody.
If you want blanched asparagus, which is a gourmet treat, mound soil around them (or otherwise exclude light from them so they do not form chlorophyll.)
At the end of the harvest, let the spears leaf out and become ferny. It can make a nice tall border. When the foliage yellows, cut it down to 2” stubs and add a 4-6” mulch of compost or leaves, which will help control weeds and feed the soil with organic matter and nutrients. If you live in an area with lots of frost, you can help protect your plants (which are hardy down to zone 4) by adding a thick layer of compost and straw to the bed.
Next Spring, be sure to weed the bed thoroughly, but pull the weeds instead of hoeing them to prevent damaging the plants, which are spreading out underground. The 6 or 13 plants you’ve planted will eventually fill out the entire bed, and you will enjoy this fantastic veggie for many, many years!
Written by Jo Ann Trigo of Two Dog Nursery. Jo Ann and Alex have many other growing guides on their site under Helpful Guides, visit them soon.