Planting, Growing, and Harvesting Asparagus
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Planting
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 (6–8 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.
When to Plant Asparagus
- Plant asparagus crowns in the early spring as soon as the soil can be worked. Many gardeners plant them at about the same time as potatoes.
- Asparagus is usually grown from 1-year-old plants called “crowns” but can also be grown from seed. Starting with asparagus crowns, however, eliminates the year of tedious weeding that comes with starting from seed and will speed up production overall.
- A few varieties, such as open-pollinated ‘Purple Passion’ and hybrid ‘Sweet Purple’, can be grown from seed. Start seeds indoors in spring and set out the seedlings when they are 12 to 14 weeks old, just after your last spring frost.
- Soak seeds in water for up to 24 hours before sowing.
- Sow seeds in moistened peat or seed-starting soil in flats or peat cups.
- Once plants reach 12 inches in height, harden them off outdoors for a week.
- After the last spring frost, transplant the young plants to a temporary garden bed. Once they mature in the fall, identify the berry-less male asparagus plants and transplant them to your permanent planting site, removing the less-productive female plants.
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 and place the asparagus crowns on top of the mound, spreading out their roots evenly.
- Within the trench, space asparagus crowns 12 to 18 inches apart (measured from root tip to root tip).
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:
Asparagus plants are either male or female. Female plants produce berries; males 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.
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.
Cooking Notes
A simple and easy favorite when it comes to asparagus is asparagus soup.
Catherine Boeckmann
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We salute you! This is an accomplishment. For advice on this we turned to Burpee, which advises “the asparagus seeds should be sown indoors 12 to 14 weeks before the target seedling set-out date, which should be after the danger of frost has passed. Sow seeds 1/4-inch deep using a sterile seeding mix in individual 2-inch cells. Acclimate in a cold frame for one week prior to setting out in the garden.” And we recognize that does not fully answer your question. The best planting time is spring. But that is a long way off—but then, so it the deep of winter. In the weeks and months remaining, harden it off (in a cold frame or for a few hours/day) and plant it, then mulch it well. And maybe remulch it if the winter becomes severe. In spring, after the heavy weather, pull off the mulch and … see if it survived. This is something of an experiment; all gardening is. If the seedlings do fail, do not consider it a failure. You brought them to life! Then go and get some crowns. Remember, even newly planted crowns need to have about two years before you can harvest. We can only speculate on how many years you might wait for your seedlings to provide harvestable spears. Good luck!
Thanks for the information! I'll give that a try. The plants are in pots ( most are in yogurt cups) They have been outside all Spring and Summer. So Harding off is done :) I'll plant as you directed and see how they do over winter. Cover with mulch (and maybe Landscape cloth that allows air and water to go through) I'll let you know in the spring how they fair thru winter. I have asparagus planted that we enjoy every spring. Just wanted to try it from seeds. Thanks again. Have a great winter!
Early spring (April) I looked up what to do this year with my three year old asparagus. It gave me the opposite advice of your website...it said to keep cutting everything that comes up as a spear, even if not going to use it. Then when it starts coming up as a fern to let it grow, which I have done. But they are still mostly spears with a few ferns here and there. I have a real mix of pencil thin, or less, and medium to really fat spears. I am confused because the other site was supposed to be experts on asparagus also! Have I badly hurt the production for next year? Have you ever heard of this approach? We got enough every other day for two people. Frankly we have gotten tired of picking AND eating or freezing. Guess I should have inquired about this earlier!
Some people would say this is a good problem to have, Beth! (Have you been giving it away? selling it??) The spears should grow into ferns. If you’re cutting the spears, they are not reaching that stage. Let it alone until fall and then cut it down and side dress (see above). It is really, really hard to kill or otherwise lose asparagus. The ferns help the plant to make food for itself, allowing it to overwinter and produce healthy new spears the following year. Next year when it comes up, harvest the spears when they are about 6 inches tall and then let the remaining asparagus grow to the fern stage.
I have a few beds of asparagus that I planted last year. The 'crop' growth was excellent. Quite a few stalks and groups came up and grew to ~4-5ft tall. I cut them back in the fall after they started dying off.
My problem is this year. Right as we expected the crop from last sprouted up along with 40% more stalks than last year. New stalks are still coming up but I also have plants that have gone to fern that are approaching 5ft and hogging all the sunlight from my peppers and lettuce.
The stalks are thick, some almost 3 pencils in circumference. I know its only August; can I cut any of the fern off yet. (I have male and female plants)
Lucky you—in so many ways. The general rule of thumb is to cut dwn the ferns in the fall. The question is (not do you feel lucky; well, not really): what is more important to you: the asparagus or the peppers and lettuce. Understandably, the question puts you betw a rock and a hard place. You want the asparagus; you want the lettuce and peppers. We would advise in this case that you leave the ‘grass alone and take of the lettuce and peppers what you can. The asparagus should be planted in a bed by itself for exactly this reason. The other vegetables, the annuals, rotate out and get picked out. But the asparagus is a perennial heavy feeder. It needs all the nutrients it can get; no competition. Next year, plant the annuals elsewhere. That’s what we would do…
Planted 5 plants this Spring, they're about 2 foot in length, have turned brown, and are now lying down. Is this normal for first year plants? Thanks in advance.
Hi Tom,
First year plants will die back late in the season, though not usually this early, but it depends on where you live. It could be over-watering, or excessive sun. At this point, don’t water them any more. You’ll have to wait and see if they come back next year!
We have a well established bed now that's 3 yrs old. This year we have numerous small ferns growing within the larger ferns. Should be transplant these elsewhere? Should we thin our asparagus?
Once all of the ferns have died down on their own (usually at first frost, but even without frost in areas that do not get frost), cut the ferns down to about 2 inches above the ground. Add several inches of mulch to the bed; compost or rotted manure is ideal. There is no “transplanting them elsewhere.” The ferns grown from crowns that are not usually divided and have, by now (in your case, after three years) very long roots. You’re growing asparagus! Enjoy it!
