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 have very old asparagus. We were told to add salt after season was over. Didn't know if this was a benifit or not.??
Any advice would be appreciated. Thanks
We have heard of using salt after the season is over to keep down weeds, but not to improve the health of the asparagus.
I live in New England. I planted crowns about a month ago (early June) following directions as best I could. It is now early July and the crowns are not showing any bit of green growth. I don't know what I did wrong. Was I too late? Is it too late now to get new root crowns and plant again or should I just wait until next spring? Should I try seeds instead?
Hi Janet,
I got my asparagus planted in early June too because of numerous delays. I actually stored the crowns in my refrigerator for 5 weeks before planting. Figuring I had nothing to lose anyway, I planted the crowns at the first opportunity I had. A couple of weeks ago I was ready to yank them all out and wait until next year to try again, but lo and behold, tiny shoots had finally appeared! I was utterly amazed. Of 10 crowns I only lost one. So, if you don't want to use those beds for other plants, just be patient. I hope your plants surprise you. Best of luck! (PS: I'm in Washington, zone 8b)
Hi, Janet. Yes, it sounds as though you planted your asparagus too late. It should go in the ground in early spring. We suggest you start fresh next year.
Thank you for the specific planting guide about asparagus. It is one of the most delicious vegetable in the world.
I have a patch of asparagus that has been left wild for likely about 20 years. I would like to dig up the crowns and move them to my garden. Any advice on which ones to dig up and how would be appreciated. I live in north central British Columbia so we have a short (100 day) growing season and cold winters.
Thanks
Hi Pam,
That’s certainly an old patch of asparagus, how do the plants look? Healthy? It’s not recommended to transplant old crowns, especially as old as 20 years. They have extremely developed root systems, and the plants would most likely be shocked by the transplant and die. However, gardening is an experiment and who knows for sure what may happen! Try transplanting the smaller crowns into a well-draining, sandy soil. Usually the crowns should be planted at a depth of 6 to 8 inches, but these may like to be deeper. Try planting a few depths between 8 to 12 inches. Water them well and see what happens. Good luck!
My asparagus plants are on their third year. We had a great crop this year. I have left them to go to fern, but they are now well over 4' tall and the wind and rain have knocked most of them over. Will this damage the crowns? You can see a deep hole at the base of the fern. What should I do if anything?
Your ferns will be OK even if they are laying on the ground. We have heard that some people prefer to steady them with a stake, but it isn’t necessary.
