Planting
When to Plant Asparagus
- Asparagus is usually grown from 1-year-old plants called “crowns,” planted about 2 to 4 weeks before your last spring frost date. Many gardeners plant them at about the same time as potatoes.
- We do not recommend growing from seed; it takes about three years to mature enough to harvest. If you plant crowns, you can shorten the wait time by a year and eliminate one year of tedious weeding. However, if you’re truly eager to experiment and have a lot of patience and time, our colleague Robin wrote about planting asparagus by seed.
Where to Plant Asparagus
Given that asparagus is a perennial plant that comes back year after year in the same spot, it’s important to select a proper planting site where it will thrive.
- Choose a site that gets full sun (6 to 8 hours of direct sunlight).
- Place the asparagus bed toward the edge of your garden, where it will not be disturbed by the activity of planting and replanting in other areas.
- Ensure the bed will drain well and not pool with water. Asparagus does not like to have its roots get too 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 neutral 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.
How to Plant Asparagus
- Plant crowns deeply to protect them from the cultivation needed for annual weed control.
- Dig a trench 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. Place the asparagus crowns on top of the mound, spreading out their roots evenly.
- Space asparagus crowns 12 to 18 inches apart (measured from root tip to root tip) within the trench.
Once you get to this point, you can follow one of two planting methods: the traditional “little-by-little” method or the easier “all-at-once” method.
“Little-by-Little” Method:
Once the trenches are dug and the crowns are set out:
- Cover the crowns with compost and topsoil, burying the crowns 2 inches deep. Water in.
- As the season progresses and spears grow to be 2 to 3 inches tall, add 2 more inches of soil to the trench, being careful not to bury the spears completely.
- Once the spears again grow through the layer of soil, add an additional 2-inch layer of soil. Repeat this process until the trench has been filled to ground level. Depending on how deep you dug your trench, you may need to add soil 1 to 2 more times throughout the season.
- After you’ve filled the trench completely, mound the soil slightly to prevent water from pooling around the emerging spears.
“All-at-Once” Method:
- 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 resulting from the “all-at-once” method. As long as the soil is fairly loose, the spears won’t have a problem pushing through to the surface.
Learn how to plant and grow an asparagus bed in our video:
Harvesting
- Skip the harvest in the first year and the second year, if possible. Ideally, wait three growing seasons before harvesting in order to allow the crowns to become fully established.
- 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 has foliage, it’s too tough for eating.
- Harvest spears when they reach 8 to 10 inches in height and between 1/2 and 3/4 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 patch in the 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 remaining ferns in summer 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 at least two or three spears on the plant through the growing season.
- Only cut 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.
How to Store Asparagus
- Plunge just-cut spears into cold water immediately to preserve their sugar content.
- Asparagus does not keep for very long after it’s picked, so be sure to eat it within 2 or 3 days from harvest.
- 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.
Types
Asparagus plants are either male or female. Female plants produce berries; male plants do not expend energy on berries, so they can be up to three times more productive than female plants. For this reason, growing male asparagus plants is often preferred.
- 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 and heat-tolerant varieties such as ‘Apollo’ and ‘UC-157’ produce well before the weather turns hot.
White asparagus is not a variety but simply asparagus grown in the absence of sunlight to prevent chlorophyll from developing. White asparagus is slightly sweeter but has less fiber than green asparagus.
Purple asparagus is bred to be purple in color but turns green when it is cooked. Purple varieties tend to have thicker spears, but fewer of them. ‘Purple Passion’ is tasty but is not an all-male variety.
Comments
It should be OK to wait to plant them in spring. Make sure that the pots are protected from freezing (such as surrounding them with a thick layer of straw mulch). Asparagus should go through a period of dormancy over winter for best spear growth. Keep them in a cool area (preferable outdoors). In late fall, after the foliage has died or has yellowed, cut them back to about an inch from the ground. Do not water or fertilize the plants over winter. In spring, begin watering again just before spears appear, and remove mulch when they do appear.
Hi, Marilyn, Apparently this is a very rare event! Folks we contacted had little to no experience with it, so there was no consensus, just opinions. These incluude
• to leave the spears, as you would first and second year growth.
• to pick the spears and enjoy them—they're a gift!
• to pick a few and leave a few, so you have the best of both worlds: a harvest and a plant allowed to mature...in which case (it occurs to us) you're blessed twice.
Hope this helps!
Normally no. Usually one lets the spears grow in spring, harvesting some of them, then letting the rest grow into ferns to make food for the plant during the season so they can survive over winter and grow again next spring. However, there is a method mentioned by the Arizona Cooperative Extension where, if you have a lot of space, for a spring/fall harvest you can grow half of your bed the above way, and half the following way: when the spears appear in spring, do not harvest them--let them grow into ferns. Then in late July, cut the ferns down. This prompts the plant to grow new spears, which you can harvest a certain percentage (just like the spring-harvested method) for a few weeks before the end of the growing season. These fall-harvested crops will always need to be only harvested in fall -- you can't also harvest from them in spring, or you will severely weaken the plants. Hope this helps!
Asparagus growing in containers will not yield as much, and will not live nearly as long as those grown in the ground, but the method does offer access to these wonderful plants to those who do not have the yard space. These plants do need lots of space, however, and will quickly outgrow a 4-gallon pot -- ideally something like 15 gallons or more is preferable - about 18 to 20 inches deep and about the same as wide. They do not like transplanting, though, so if you decide to transfer them to a larger pot, wait until they are dormant in fall or winter.
For general care, wait for the ferns to die back in the fall, then cut them down to about 3 inches. Provide mulch over the crowns (some use the cut down ferns) and protect them appropriately from winter's cold, depending on your climate (they do require some period of cold temperatures). In spring, side-dress with organic fertilizer, scratching it into the surface, and then add some compost. Be sure your pot has good drainage, and that it is set in an area where the plant can get about 6 to 8 hours full sun. Water consistently (when dry about 2 inches into soil -- do not overwater).
Do not harvest from the plants until the second year after they were planted in the container (so yours would then be 4 years old if you planted 2-yr crowns in spring 2016--if you transplant them again into another pot, you ideally should wait another year again -- you can play it by ear, and monitor the vigor of the plants as they come up that second year).
For more advice for growing asparagus in your area, you might try contacting your county's Cooperative Extension. For contact information, see:
http://www.almanac.com/content/cooperative-extension-services
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With good care and environmental conditions, asparagus crowns may remain productive for 15 to 20 years, sometimes even more.