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How to Grow Asparagus

Asparagus (Asparagus officinalis) is a perennial vegetable plant native to Europe and northern Africa. Having a life span of almost 20 years and an attractive fernlike form, the plant is often used as borders for the garden and is a popular choice for edible landscaping. The asparagus plant has a relatively high water content of almost 93%, with its young shoots popularly consumed raw, for their fine texture and taste.

Growing Conditions

USDA Hardiness Zones 4 to 9
Sun Exposure Full Sun
Planting Season Late Winter
Temperature 45°F-75°F
Soil Type Sandy
Soil pH Slightly Acidic to Neutral

How Does Asparagus Grow?

The Asparagus plant has broad feathery foliage and can grow up to 150cm tall. Its spears are usually 6-8 inches in length with straight shoots and scaly tips. The plant produces small bell shaped flowers that occur either singly or in clusters. Usually asparagus is a dioecious plant, with male and female flowers on separate plants, though hermaphrodite variants are also known to exist. Male plants are preferred among growers over the female, as they do not spend energy on producing seeds and fruits, resulting in a considerably higher yield of stalks. Asparagus shoots are safe for consumption but its fruit (small red berries) can be poisonous to humans.

Asparagus Shoot and Berries

Asparagus Shoot and Berries

Types of Asparagus

A large number of hybrid Asparagus varieties are available with some popular choices being:

  • Mary Washington and Martha Washington both are among the most commonly found heirloom varieties of asparagus. They are open pollinated variants and are an excellent choice for your garden.
  • Jersey Giant is an extra long, all-male hybrid variety that is highly productive and resistant to several diseases. It is also preferred among several commercial asparagus farms.
  • Purple Passion isa sweet asparagus variety which is bred to be purple in color. They tend to have thicker but fewer spears.
  • White Asparagus is simply asparagus grown in the absence of sunlight to prevent chlorophyll development. White asparagus tends to be sweeter and contain less fiber when compared to the usual green variety.

Growing Asparagus: Seeds vs. Crown

Since it takes a lot of time and patience to start an asparagus patch from seeds, most people prefer to use asparagus root mass and crown. But it should be known that starting the patch from a bunch of seeds has a variety of benefits like:

  • Seed-grown plants don’t suffer from transplant trauma like nursery-grown roots
  • A packet of asparagus seeds cost less compared to buying several root crowns
  • Seed grown plants eventually tend to out-produce those grown from roots
  • Growing from seeds enables you to discard any female plant and have only male plants in your garden.

How to Grow Asparagus from Seeds

  • Seeds should be started once the danger of frost is past
  • Place the seeds approximately ½ inch deep in the soil. Dipping the seeds in water or keeping them in a refrigerator prior to sowing aids in the germination process.
Asparagus Seedlings Picture

Asparagus Seedlings Picture

  • In 6-8 weeks the seeds will begin to sprout
  • Shield the seedlings from strong winds and take measures to limit their exposure to direct sun.

Transplanting Asparagus

Seeds can also be sprouted indoors or in your greenhouse. Once seedlings are a foot tall they can be transplanted 2-3 inches deep either in a container or in the garden patch. Care should be taken to lift the seedling with as little disturbance to the roots as possible. Then place them in their new position by gently spreading the roots down away from the crown and covering it up with soil.

Planting Asparagus Crowns

  • Planting of crowns begins when they are still dormant (around late winter).But if plump, healthy roots are available they can also be planted as late as mid-spring. Use only firm and fresh root masses by pruning out any dry sections before planting.
  • Prepare the soil by removing any weed and adding a layer of sundried manure and compost.
  • The crowns will need to be covered as they grow. The best way to plant asparagus is in a shallow trench 6-8 inches deep.
Asparagus Crown Picture

Asparagus Crown Picture

  • Shallower plantings yield many spindly spears, while those planted deeper produce fewer spears of larger diameter. Place the crowns 15 to 18 inches apart in the furrow, and cover initially with 2 inches to 3 inches of soil.
  • Water thoroughly immediately after planting. It should be noted that asparagus does not perform well in perpetually wet soil. Make sure the soil has good drainage or place the plants on raised beds to avoid damage from standing water.
  •  As the stems emerge, gradually start filling the trench with soil, leaving only 3-4inches of the top stem exposed.

Companion Planting

Asparagus performs well when planted with tomatoes. The tomato plant repels the asparagus beetles whereas asparagus helps repel root nematodes that may be harmful for the tomato plant.

Growing Asparagus Indoors in Containers

Asparagus can be grown in your home in large pots and containers for a limited time. Container grown asparagus does not live as long as crowns planted in the ground. Following the two year establishment period the container-grown plants will be productive only for 3-4 years under ideal conditions.

Picture of Growing Asparagus Indoor

Picture of Growing Asparagus Indoor

  • Choose a container which is at least 8 inches deep and 6 inches wide so as to be able to accommodate the plant at maturity.
  • Water at regular intervals and place the container at a window sill that receives full sunlight.
  • Cooler temperatures are required by the plant during winter periods to maintain its natural cycle. Therefore it is important to move your container outdoors, in an appropriate location, during this period.

Asparagus Care and Maintenance Tips

  • Eliminate weeds regularly from your patch as they deprive the soil of nutrients and propagate pests. This can be done using a hoe or a rotary tiller. Many gardeners also use coarse salts to control weeds. Asparagus tolerates salt better than most plants.
  • Trimming off any yellow foliage and removing dead or decaying plant matter helps to prevent rot.
  • During spring feed the plant, especially the ones growing in containers, with a general all-purpose fertilizer. Use compost regularly to replenish an organic asparagus plant-bed.
  • Add a thick layer of mulch every year as it helps to regulate moisture in the soil.

Diseases and Pests

Rust: The disease begins to show itself between spring and early summer and is characterized by small rust colored lesions on the plant.

Fusarium stem and crown rot: If your asparagus ferns start to wilt before autumn with their roots turning slightly black, chances are that they have been afflicted with the fusarium stem and crown rot.

Asparagus beetle:  The asparagus beetle can nibble on spears and lay dark eggs along the surface.

Fungicides work well against rust but they should be sprayed in the early stages of the onset of the disease to be effective. Several disease resistant varieties of the plant are available that offer protection against fusarium. The beetles can be hand-picked and its eggs can be scraped off using your fingernails.In case of an infestation insecticides can also be used.

Harvesting

Asparagus should be cut when they are around 6 inches (15cm) tall. Use a sharp knife to cut individual spears roughly 2cm below ground level.

Harvesting Asparagus

Harvesting Asparagus

  • Do not harvest the asparagus plant in its first year. This enables the plant to develop healthier stems and roots resulting in a longer plant life and higher productivity in subsequent years.
  • During the second year, a limited harvest can be performed during April and May.
  • By third year onwards a full harvest can be made. It is generally advised to stop cutting your asparagus plant from the end of May. Later harvests can be made but it reduces the chances of the shoots developing foliage resulting in weakening of the plant.

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