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 re-planting 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 are planted.
- 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, either. 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 two or three 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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Asparagus does best with a chilling period, but there are cases where it can be grown in a tropical environment. One source says it can be done as long as there is a long enough dry season to induce dormancy. Here is an article about growing it in Hawaii, which says that it does not undergo winter dormancy, so it can be harvested several times a year. There are instructions about how to induce dormancy during the drier summer months.
https://www.ctahr.hawaii.edu/oc/freepubs/pdf/HGV-9.pdf
Hope this helps!
I just planted seeds and I now have little ferns in containers. What's next and when do I plant them in their permanent home? Do I plant them in one spot and then move them again or is that only when using crowns?
When asparagus transplants are about 1 foot tall, they need to be set out in a nursery bed after the last expected spring frost date, and when the soil is warm. (To find your frost date, see: http://www.almanac.com/gardening/frostdates). Before you transplant, harden them off for a week in a protected area or cold frame. (You can also direct seed in the garden in early spring.) When the plants flower in their nursery bed, weed out the female plants. The following year, transplant the male plants to their permanent home. If grown from seed rather than crowns, add another year before you should harvest fully (3 years).
For more information, you might like this blog about planting asparagus from seed:
http://www.almanac.com/blog/gardening/gardening/planting-asparagus-seed
Happy gardening!
Is it too late to plant crowns in upstate NY (Finger Lakes region)? Have had a bed producing for 20+ years and all of a sudden it seems it about done.
Cornell University suggests planting crowns 4 to 6 weeks before average last frost. To find your frost date, you can go to the following page and put in your zip code.
http://www.almanac.com/gardening/frostdates
If you have further questions, you might contact a local nursery or your county’s Cooperative Extension. Extension contact information can be found here:
http://www.almanac.com/content/cooperative-extension-services
Hope this helps!
My seven year old asparagus bed seems to be getting broad leaves instead of spears when they are about 4 inches tall ? Has anyone heard of this or know of a potential cure ?
I love Asparagus and I am going to plant this spring. I'm concerned about our elevation in Cheyenne Wyoming and how it will effect the Asparagus......any other concerns come to mind?
You should choose a hardy variety of asparagus. Two hardy varieties we would recommend are ‘Jersey Giant’ or ‘Mary Washington.’ Good luck!
Hello Meghan,
I work at a local garden ctr. and asparagus is now just becoming available to us from the growers & I've spoke with local gardeners and their asparagus is just starting to peek thru :)
Hi there,
I recently moved into a house in the Durham Region area of Ontario. I knew the previous owners and they informed me of a thriving asparagus bed in the back garden. I'm totally new to gardening, so I'm not really sure when to expect the crowns to start coming up in my area. I thought I would have had some action by now, but nada. Any idea when I might expect to start harvesting? Thanks!!
