How to Grow Asparagus From Seed

Saving money is one of several advantages of starting asparagus from seed. Here’s how you can benefit.

September 13, 2019

Photo by: Shutterstock/DUSAN ZIDAR

Shutterstock/DUSAN ZIDAR

By: Margeaux Emery

Growing asparagus from seed truly takes patience. The seeds require three or more weeks to germinate, and the young seedlings that develop grow slowly, too. Yet as with so many things in life, patience brings rewards. Starting from seed saves money. For less than the cost of one asparagus crown — the nursery-grown roots that many purchase to start an asparagus plant with — you can buy a packet of seed capable of growing up to a hundred or more plants. As a rule of thumb, 50 plants are regarded as sufficient to feed a family of four.

Seed-grown asparagus has other pluses, too.

  • It is not at risk of the transplant trauma that sometimes affects crowns or purchased young plants from a garden center.
  • Asparagus plants started from seed eventually will out-produce ones grown from crowns.

Growing from seed enables you to identify and remove female asparagus plants early so that you can plant an all-male bed to grow the most spears.

First, Prepare the Bed

Before even purchasing asparagus seed, you may want to get an early start on preparing a bed for them.

These points will help you find a good spot:

  • Plant in full sun for the healthiest plants and harvests, although asparagus can tolerate partial shade.
  • Soil that drains well is critical. Grow in raised beds if your soil is poor or is constantly wet.
  • Asparagus plants can produce harvests for up to 30 years (or more), so choose a spot where the plants can be left undisturbed and will be out of your way.
  • Avoid locations with strong winds.
  • Consider the plant’s beauty. You may wish to use asparagus as an ornamental in your landscape and plant where the bed is in line of sight. You can also use asparagus as a living green screen to hide a fence or unwanted view.

Next, remove all weeds and grass from the intended bed. Loosen the soil and incorporate two to four inches of organic matter such as compost or aged manure to a depth of eight inches.

A soil test will give you important information on pH and fertilization recommendations. The optimum pH range for asparagus is 6.5 to 7.0. If adjustments need to be made, it’s good to do so in the fall prior to planting, to allow the amendments to settle in over winter. If done this way, cover the soil with mulch or plant a cool-season cover crop. A cover crop not only protects the soil, but it will also add valuable organic material to it when you turn it under before spring planting.

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How to Start Seeds

Many varieties of asparagus are available. Choose one suited to your growing zone. Most are hardy in zones 3 to 8.

Sow asparagus seeds indoors eight to 12 weeks before transplanting outside after the risk of frost has passed. Plant the seeds 1/4 to 1/2 inch deep in a sterile seed mix. Place the tray or pots in a sunny, warm location and keep the soil moist. Germination may take 14 to 21 days or longer. Don’t give up. A week before transplanting, harden off the seedlings in a cold frame or protected area such as a covered porch. When seedlings are two inches tall, transplant into a prepared bed, spacing 12 to 18 inches apart. Plants can be grown in single or double rows. Refer to the seed packet for a variety’s specific recommended spacing.

Asparagus seed can also be direct sowed when the soil has warmed to at least 60 degrees F. Plant seeds 3/4 to one inch deep. Gently firm the soil and keep it evenly moist while the seeds germinate. Seedlings can emerge in 10 to 14 days when the soil temperature is 75 degrees F. Thin seedlings after they grow their first set of true leaves. Asparagus can also be planted in the fall.

How to Grow

  • Weeds and grass must be kept at bay at all times. This is the most critical point of care because asparagus cannot compete for water, space and nutrients. Control weeds and grass by cultivation or use of mulch.
  • Mulch will also help retain moisture and regulate soil temperature. Create a cost-effective mulch by laying five to 10 sheets of newspaper between asparagus rows. Wet the paper to hold it in place and cover with leaf compost, grass clippings, straw, or other yard wastes. Keep plant stems free of mulch to avoid rot.
  • Watering is vital for the first three years. Soil needs to be moist but not saturated. Use irrigation or water early in the day to ensure foliage is dry by nightfall.
  • If pests and diseases appear, contact your local Cooperative Extension Service for recommendations of controls that work well in your area.
  • Fertilize in spring (after harvests, as the plants mature) and in late summer with a liquid fertilizer, compost tea or granular, balanced fertilizer.
  • Allow plants to grow through fall. When fronds brown, cut them two inches above ground and remove the spent foliage from the area. Add mulch at this time if your area has cold winters.

Harvesting

The thought of tender-crisp asparagus fresh from your garden is tantalizing. Yet here, too, patience is required to provide time for the plants to establish and build their strength. The first year after planting, it’s ok to harvest a few spears from each plant across a two-week period. Leave the rest to grow and feed the plant’s root system. The next year, you can harvest for three weeks, and in subsequent years, for four to six weeks, until new stalks are thin and spindly. Stop there to ensure the plant retains its strength to flourish the following year.

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