How To Plant asparagus

General Introduction

Asparagus is one of the first plants that greets us in springtime! It’s a perennial, which means that once it gets established, the tender spears will return year after year. In addition, its ferny foliage makes an excellent ornamental. Here’s how to grow asparagus—from planting through harvest.

Asparagus can be grown in most parts of the country but grows more robustly in cooler regions with longer winters. The edible part of the asparagus plant is the young stem shoot, which emerges as soil temperatures rise above 50 degrees Fahrenheit in spring. 

The most important thing to know about asparagus is that you really should not harvest it for the first couple seasons. Plants need to be allowed to mature before you can harvest. The patience is rewarded because the asparagus bed will be productive for 15, 20, sometimes 30 years. 

Because asparagus stays productive for so long, it’s important to plant the best variety available for your area. (See varieties below.)

Plant in early spring as soon as the soil can be worked. Age of Asparagus is usually grown from 1-year-old plants or “crowns” (bought at a garden center) but it can also be grown from seed. Starting with asparagus crowns, however, eliminates the year of tedious weeding that comes with starting from seed.

If you are starting asparagus for the first time, we would plant 10 to 20 asparagus plants per person (15 to 30 feet of row).

As said above, newly-planted asparagus plants may take 2 to 3 years to truly get started and produce, so patience is needed! After they’re established, however, asparagus is productive for decades.

In addition, asparagus plants are fairly fast producers, sending up new spears every few days for a few weeks in the spring. The plant produces ½ pound of spears per foot of row in spring and early summer, so we think it’s definitely worth the wait.

Planting

  • Plant asparagus crowns in the early spring, as soon as the soil can be worked. Many gardeners plant about the same time potatoes go in the ground. 
  • A few varieties, such as open-pollinated ‘Purple Passion’ and hybrid ‘Sweet Purple,’ can be grown from seed. Start seeds indoors in spring and set out the seedlings when they are 12 to 14 weeks old, just after your last spring frost. Soak seeds in water for up to 24 hours before sowing. Sow seeds in moistened peat or seed-starting soil in flats or peat cups. Once plants reach 12 inches in height, harden them off outdoors for a week. After the last spring frost, transplant the young plants to a temporary garden bed. Once they mature in the fall, identify the berry-less male asparagus plants and transplant them to your permanent planting site, removing the less-productive female plants.
  • Soak seeds in water for up to 24 hours before sowing.
  • Sow seeds in moistened peat or seed-starting soil in flats or peat cups.
  • Once plants reach 12 inches in height, harden them off outdoors for a week.
  • After the last spring frost, transplant the young plants to a temporary garden bed. Once they mature in the fall, identify the berry-less male asparagus plants and transplant them to your permanent planting site, removing the less-productive female plants.
  • Choose a site that has at least partial sun.
  • Place the aspargus bed toward the edge of your garden where it will not be disturbed by the activity of planting and re-planting other areas.
  • Ensure the bed will drain well and not pool water. Asparagus does not like to have its feet “wet.” If you do not have a site with good drainage available, consider growing asparagus in raised beds instead. Learn how to make a raised garden bed here.
  • Asparagus thrives in netural to slightly acidic soil (pH of about 6.5).
  • Eliminate all weeds from the planting site, digging it over and working in a 2- to 4-inch layer of compost, aged manure, or soil mix. (Learn more about soil amendments and preparing soil for planting.)
  • The soil should be loosened to 12 to 15 inches in depth to allow the asparagus crowns to root properly and not be disrupted by rocks or other obstacles. 
  • Plant crowns deeply to protect them from the cultivation needed for annual weed control.
  • Dig a trench of about 12 to 18 inches wide and 6 to 8 inches deep. If digging more than one trench, space the trenches at least 3 feet apart.
  • Soak the crowns briefly in lukewarm water before planting. 
  • Make a 2-inch-high ridge of soil along the center of the trench and place the asparagus crowns on top of the mound, spreading their roots out evenly.
  • Within the trench, space asparagus crowns 12 to 18 inches apart (measured from root tip to root tip).
  • Some gardeners simply fill in the trench with soil and compost all at once. While it’s thought that the traditional method results in stronger plants overall, gardeners don’t typically have any issues result from the “all-at-once” method, either. As long as the soil is fairly loose, the spears won’t have a problem pushing through to the surface.

Care

  • When the trench is filled, we would add a 4- to 6-inch layer of mulch.
  • The biggest issue with asparagus is managing weeds during the first two years. Asparagus can not have its roots disturbed so you’ll need to gently hand pull weeds, taking care not to disturb roots. Weeds will become less of an issue as the plants fill in. Mulch around the plant with compost or grass clippings to help soil moisture and reduce weed growth.
  • During the first 2 years after planting, asparagus plants need 1 to 2 inches per week. If you are not receiving adequate rainfall you will need to water. Use drip irrigation if possible.
  • Asparagus thrive on a steady supply of plant food. Consider an organic fertilizer during the growing season. Follow the label on the product.

Pests/Diseases

  • Asparagus is considered a deer-resistant plant, though a hungry deer will eat almost anything.

Harvest/Storage

  • Do not harvest the first couple seasons (see information above).
  • If you have young plants, the season may last 2 to 3 weeks. However, established plants produce longer—up to 8 weeks.
  • Check your plant every other day for harvest-ready spears. Spears grow quickly and may become too woody before you know it! Once an asparagus spear starts to open and have foliage, it’s too tough for eating.
  • Harvest spears when they reach 8 to 10 inches in height and between ½ and ¾ inch thick. (Bear in mind that younger, thinner spears will be more tender, so harvest according to your own taste.)
  • To harvest asparagus, simply cut the spears with a sharp knife or scissors at ground level.
  • Stop harvesting spears when the diameter of the spears decreases to the size of a pencil.
  • After harvest, fertilize your asparagus in early summer. You can top-dress with a balanced organic fertilizer, or scatter another inch of rich, weed-free compost over the decomposing mulch.
  • Do NOT cut down the ferns or you will ruin your asparagus bed. Allow the ferns to grow and mature; this replenishes the nutrients for next year’s spear production. Always leave one or two spears.
  • Only back asparagus ferns AFTER the foliage has died back and turned brown or yellow. This is usually in early winter after several hard freezes. Cut the ferns back to the ground.
  • Fertilize the bed with a 1-inch layer of rich, weed-free compost or manure topped with 3 inches of straw, rotted sawdust or another weed-free mulch. Clean spears will push up through the mulch in spring.
  • Asparagus does not keep for very long after it’s picked, so be sure to eat it within two or three days from harvest.
  • Brush off any visible dirt or give the spears a light washing with cold water before storing. It’s very important to dry washed spears thoroughly; moisture can lead to mold.
  • To store, bundle the spears together, wrap the stem ends of the spears in a moist paper towel, and place the bundle in a plastic bag. Store in the crisper drawer of your refrigerator.
  • If you have enough space in your fridge, you can also store asparagus by placing the spears in a cup of water. Keep about an inch of clean water in the cup.

Recommended Varieties

  • Gardeners in Zones 4 to 6 have a wider selection of varieties, including ‘Jersey Giant’, ‘Jersey King’, and ‘Jersey Knight’. Older varieties ‘Mary Washington’ and ‘Martha Washington’ may produce female plants, which are not as productive as the males.
  • In colder climates, ‘Guelph Millennium’ and other varieties that emerge late often escape damage from spring freezes.
  • In warmer climates, early, heat-tolerant varieties such as ‘Apollo’ and ‘UC -157’ produce well before the weather turns hot.

Wit & Wisdom

  • A pinch of baking soda in the cooking water keeps beans, spinach, and asparagus greener.
  • At only 40 calories per cup, asparagus is amazingly good for you! See our list of awesome asparagus health benefits.
  • For more planting tips, see our page on growing asparagus from seed.

Recipes

  • Alton brown asparagus recipes:
  • Roasted Asparagus with Black Olive Aioli
  • Asparagus Tart
  • Asparagus Hummus Served With Dukkah-Spiced Pita Chips
  • Asparagus Vinaigrette Salad
  • Lemony Asparagus and Spring Pea Salad with Roasted Almonds
  • Prosciutto-Wrapped Asparagus

How To Plant asparagus


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