How To Grow Asparagus
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By: Jackie Rhoades
Asparagus (Asparagus officinalis) is a long lasting perennial, and the first vegetable harvested each spring. It’s prized for its flavor, rich in vitamins and minerals, and only 30 calories per cup. Add to this the grocery price and you’ll easily justify the effort of digging a special bed for growing asparagus.
Asparagus Growing Conditions
Production can last 15 years in a well placed bed of asparagus. Care should be taken to find a spot that will receive at least eight hours of sunlight in a well drained area that can be deeply dug to properly plant your asparagus. Growing conditions should be given the greatest consideration since the bed will be more or less permanent.
How to Grow Asparagus
Knowing how to grow asparagus will give you the healthiest plants with the greatest yield. Buy one-year-old, healthy crowns. Dig a trench 8 to 10 inches (20-25 cm.) deep and wide enough to accommodate the growing asparagus roots. Apply one pound of triple superphosphate (0-46-0) or 2 pounds of superphosphate (0-20-0) for every 50 feet (15 m.) of trench.
For ideal growing, asparagus trenches should be 4 feet (1 m.) apart. Place the crowns 18 inches (46 cm.) apart right on top of the fertilizer. Work liberal amounts of organic material into the dug soil to provide optimal asparagus growing conditions. Use this soil to backfill the trench to a depth of 2 inches (5 cm.).
Backfill with more soil every time you see another 2 inches (5 cm.) of the tender new stalks of asparagus. Care must be taken to protect these delicate shoots. Once the trench is filled, the hard work is done, but there is a little more to know about how to grow asparagus successfully.
Weed the bed thoroughly in early spring to keep the bed weed free. Feed the growing asparagus annually with a 10-10-10 granular fertilizer. Don’t harvest until the third year and then only lightly. Thereafter, harvest up until July 1st by snapping the stalks off at the base. Then, the growing asparagus should be allowed to reach maturity to insure the development of healthy roots.
If you follow these simple directions for asparagus care, you’ll enjoy those tender and delicious spears for years to come.
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Read more about Asparagus
Asparagus Spacing In Raised Beds
A dedicated asparagus bed will produce year after year. Source: minicooper93402
Normally, you would plant asparagus crowns or seeds 18 inches apart in rows, which are then spaced several feet apart from each other. This protects the delicate root systems and allows the plant lots of room to spread out, and room for you to walk along the rows and access your plants as you care for them.
In a raised bed, you don’t have to space the “rows” so far apart! Because you can walk around your bed easily, there is no need for large rows to access your plants. You can simply space the asparagus crowns 18 inches apart from every other plant. This allows for a greater density of plants in a smaller area, while still allowing plenty of room for future growth.
Growing asparagus in Oregon requires patience, but it’s worth the wait
A grower weeds her asparagus bed by hand as the asparagus is beginning to sprout. Doug Beghtel/Staff
CORVALLIS – Growing asparagus requires patience – from planting to harvest takes two to three years, but the wait is well worth the reward.
Homegrown asparagus is one of the earliest vegetables of spring. Its quality is much better than store-bought spears, and it’s less expensive. Once established, this vegetable is easy to grow. And asparagus is beautiful. A member of the lily family, its fern-like foliage turns from green to gold in fall, and can be a backdrop to chrysanthemums or other late-season flowers.
Oregon State University Extension Service horticulturists say preparing an asparagus bed properly will reward you for decades.
Asparagus is a hardy perennial and should be planted as soon as the soil can be properly prepared in the spring. Usually asparagus is started from 1-year-old plants, rather than from seed. The plants you purchase in early spring are dormant crowns (no leaves) and look like an octopus, with long fleshy roots extending from the crown. Avoid buying crowns that are dried out or have rotten areas. If you can’t plant the crowns right away, keep them cool and moist until you are able to get them in the ground.
A bed of asparagus, left to form ferns, yellows in the chill of fall. Randy L. Rasmussen/Staff
Choose a site for the asparagus in full sun. Foliage will reach a height of 5 to 6 feet during the summer so place your asparagus bed where it won’t shade out smaller plants. Good soil preparation is a key to success. It’s important to dig deeply to remove weeds and amend the soil with plenty of organic matter. Asparagus will not grow well in heavy, poorly drained soils and doesn’t compete well with weeds. Prepare the growing site to a depth of at least 12 inches and add a general slow-release fertilizer, Check the pH with a do-it-yourself test from a garden center or a laboratory, and add lime if you soil is acidic.
Plant your asparagus crowns into the prepared bed about three to four weeks before the last frost date. After amending the soil, dig a trench about 6 inches deep, place the crowns at the bottom of the trench about 12 inches apart. Place the bud pointing up, spread the roots and cover the crowns with 2 inches of the soil from the bed. As the spears lengthen through the spring, fill in the trench with soil, leaving the tips exposed. Keep the soil moisture consistent through the first year so the asparagus crowns can get established.
Starting from seed is less common but can be a less expensive way to make an asparagus bed. It will take an extra year (four rather than three) for seed-started asparagus to reach a harvestable stage. For information on growing seeds, we have a video (above), as well as an article. You can search the OSU Extension publications catalog or news feed for more resources.
Do not harvest the spears the first spring of planting. They should be left to form “ferns,” which provide food for the plant. The second spring after planting, a few shoots can be harvested, but only for a week or two. Leave the rest to feed developing roots. The third spring and thereafter, harvest spears until mid-June, then allow the fern to grow and keep the root crown healthy.
Asparagus should be fertilized in the spring as spears emerge and again right after the last harvest in June for older plantings.
To harvest, grasp 5- to 8-inch-long spears at the base and bend them toward the ground. The spear will snap where it is free of fiber. Spears may also be cut with a knife, but make sure not to damage the emerging spears. Quality deteriorates rapidly after harvest. If you can’t eat your asparagus immediately, refrigerate or process it.
Information on how to pickle asparagus is in the online OSU publication PNW 355 “Pickling Vegetables.”
Asparagus varieties recommended for Oregon by OSU include Mary Washington, Jersey Knight, Jersey Giant, UC 157, Purple Passion, Sweet Purple and Millennium.
Harvest and Storage
Asparagus harvest begins in Year 3. Plants may be harvested for up to 4 weeks in Year 3. Cut 9 inch tall spears at ground level. Harvest all spears since tall growing spears suppress further spear growth. Harvest for 6 weeks in Year 4 and up to 8 weeks after 5 years of growth. Stop harvesting when the majority of spears are smaller than a pencil in diameter. In most areas, stop harvest by early to mid-June.
After Harvest Plant Care
After harvest is completed, control weeds and allow spears to develop into fern. Fertilize the beds, water regularly, and control pests. After ferns die in the fall, mow them down and use as a soil mulch. Avoid tilling asparagus beds since this damages the crown. Use mulches and herbicides to control weeds.
A mature asparagus plant can produce Вѕ pound of spears/plant during the harvest period. 25 plants should provide sufficient spears for fresh consumption and storage purposes. Spears will store for 3-5 days at 35В°F and 95% relative humidity.
Frequently Asked Questions
How long will asparagus last?
Expect the plant to produce spears for 10-15 years.
Why are the spears always skinny?
Plants may have been water stressed last summer. New spears form in July and August so stress (water, heat, etc.) will affect their size. Plants need healthy fern to grow and store enough food for good spear growth. As the harvest season progresses spear size naturally decreases.
Can you harvest asparagus at other times of the year beside spring?
Yes you can but generally these plants do not yield well and the life span of the bed is greatly reduced.
Can you grow white asparagus in Utah?
Yes but you need to mound soil over the planted bed and then cut the spears just as they poke through the soil. If light gets to the spear it will turn green. Use black plastic in the spring to cover the beds. This will keep the light out.