How to Plant Asparagus

Asparagus is a perennial plant that can last up to 15 years. Its crisp, tender spears make it pair well with meats such as salmon, steak, and scallops. Due to its longevity, you should plant varieties suited to your area, or ones that fit your culinary preferences. It is important to realize that asparagus can take several seasons before it can become established enough to be harvested. Although asparagus can be planted in most temperate areas, it grows especially well in cooler regions with long winters. 

cooked asparagus

Spears are known as the edible part of plants, which is also its stem. The stem is connected to underground buds that develop from a root system, which are called crowns. A sign of spring, the stems emerge from the soil as temperatures rise above 50 °F. While it can take 2 – 3 years for plants to become productive, planting asparagus eventually pays off. It is fairly proliferative, producing about ½ pound of spears per foot in spring and early summer. Before planting asparagus, make sure you are willing to dedicate the time and space to it, as it can take up a lot of space and comes back for up to 20 years. 

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BASIC INFORMATION

Scientific Name

Asparagus officinalis

Plant Type

Vegetable

Sun Exposure

Full sun

Soil Type

Loamysandy, well-draining soil high in phosphate

Soil pH

6.5 – 7 

Bloom Time

Spring

Flower Color

Yellow

Hardiness Zones

456789

Selecting Plants

While green is the most common color, Asparagus can come in purple and white varieties. Purple asparagus contains high levels of Anthocyanins, a class of compounds with antioxidant effects including anti-inflammatory, anti-viral, and anti-cancer benefits. White asparagus is grown in the dark, which prevents it from turning green, and has the same taste and texture as green asparagus. It is considered a delicacy in Europe and more expensive because it requires more effort to grow. 

fried asparagus

Asparagus is dioecious, which means that it has female and male plants. While all produce edible spears, female plants produce red, inedible berries during the summer and grow larger spears. Male plants have better-spear production and tend to live longer. Male hybrid varieties, such as Jersey Giant, are plants with male flowers that produce new seeds. If high production is not a priority and you are an experienced gardener, you may want to explore some heirloom varieties, which produce beautiful plants. 

  • Jersey Giant – High yield, disease resistant, mostly male plants, great flavor
  • Jersey Knight – Vigorous flavor and large, succulent spears. Highly resistant to most diseases. Hardy in freeze areas.
  • Purple Passion – Unique purple color and wide-stemmed with a mild, nutty flavor. 
  • Mary Washington – Rust-resistant, deep-green spears with tips of light purple. Grows uniformly and produces long, tender shoots. Heirloom variety.
  • Precoce D’Argenteuil – Heirloom variety with rose-colored buds. Very sweet taste. Earlier harvest, which can be derived partly from its name.

Growing Asparagus

When to Plant: Asparagus can live for 20 years, so you should select the location carefully. Avoid areas with shallow soils or prone to water-saturation. It prefers a temperature of 70 – 85 °F during the day and 60 – 70 °F during the night. It can be planted both during the fall and spring. Asparagus grows well in sandy soil rich in organic matter. 

growing asparagus

Since it requires well-drained soil that holds moisture well and has a deep root system, raised garden beds are an ideal option for growing asparagus. There are many benefits to starting asparagus in raised metal beds, including control over soil quality, ease of maintenance, and more rapid soil warming. While asparagus can be started from seed, it is commonly planted as crowns that are two years old and have long roots.  

How to Plant: Prepare your soil with organic matter such as compost and amendments to ensure adequate nutrients. Normally, asparagus are spaced 18 inches apart in rows, which are then spaced several feet apart from each other. In raised beds, you can simply space the asparagus crowns 18 inches apart on each side.

Dig holes that are 12 inches deep and place the crown or seed into the hole. Fill the hole with soil. Alternatively, they can also be planted in a trench. Dig a depression that is 6 – 8 inches deep and set the crown into the furrow at 18-inch intervals. Cover the crowns 2 – 3 inches of soil that was removed previously and water immediately after planting. Use the remaining soil to add to the trench later, once the plants have emerged and the spears are 2 – 3 inches tall, adding about 2 inches. Repeat this process until you have finished filling the trench.

Caring for Asparagus: Asparagus plants should receive about an inch of water per week. You can consider setting up a drip irrigation system or use a soaker hose. It is recommended that you add mulch to reduce weed growth and retain moisture. Fill any open space with companion or cover crops to maximize productivity. Since asparagus thrives on a steady supply of plant food, organic fertilizer should be added during the growing season, which is usually late summer or early fall.

Pests: A common pest is the asparagus beetle, which are oval-shaped and either reddish-orange with black spots or black with six white spots on its back. They chew through the spears and leaves. If you notice asparagus beetles on your plants, handpick them and throw them into a bucket of soapy water. Neem oil or pesticides such as pyrethrin or malathion can be used in cases of serious infestations without causing harm to beneficial insects. Other pests such as aphids and thrips can be eliminated by applying neem oil. If you have a raised garden bed, you can set up floating row covers over it to prevent pests from climbing over. 

How to Harvest Asparagus

If you have planted your asparagus from seed, you should avoid harvesting it for the first and second year to allow the plants to fully develop. In the third year, you can harvest for two to four weeks, stopping when the spears are narrower than half an inch in diameter, or the size of a pencil. Spears should be harvested when they are 6 – 8 inches high. In subsequent years, you can gradually increase the harvest amount to up to 8 weeks. 

For asparagus with planted crowns, you should wait a year and not harvest and refrain from harvest until the second year. To harvest, use a knife and cut them off just above soil level. You can also use your hand and snap the spears. If the tip of the spear has started to crack open, it will be unpleasant to eat, and should be composted. 

Once the harvest season has ended in late spring or early summer, the spears will grow to 4 – 6 ft high, with lacy fronds. It is important to keep the area watered and mulched. Once the fronds turn yellow, cut off and remove the fronds from the area, leaving a few inches above ground level. If you live in an area with harsh winters, leave the fronds in place and remove them in the spring. 

Cover the harvested asparagus with a plastic bag and store in the refrigerator for up to a week. For longer term storage, blanch them in boiling water for 3 – 5 minutes before dropping it in cold water. Drain the water and let it air-dry. Afterwards, store in the refrigerator. 


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