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.
It's best not to till an asparagus bed, as you might damage the crowns. Early in the season, before growth emerges, it is possible to use a hoe to remove weeds shallowly, but at the current stage, where you have young and ready-to-harvest spears, hand pulling is best to avoid damage. After you remove the weeds, a 3- or 4-inch layer of organic mulch, such as straw (not hay, which may have seedheads), can help prevent further weed emergence.
Asparagus may fern early in hot temperatures or drought. Make sure that your plants are getting enough water. Also, that they are receiving a topdressing of fertilizer each year. If they run out of nutrients, the spears may be small. Thin spears may also be a sign of age (which would not be the case in a 5-year-old bed) or harvesting too many spears, which can stress the plant. Also, be sure to only remove the ferns after they have completely browned. If removed too early, the plant can't make enough food for it to survive well, causing weak growth next year.
Hi Valerie,
Do not cut or pull the stems. You may disturb roots that are still growing. Add some compost to the soil and in the fall cover your beds with mulch to protect the roots from freezing temperatures.
If you have a small bed, you can handpick weeds as they emerge, being careful of the asparagus crowns. Mulch also will help to supress them, and some gardeners find that a 3- to 4-inch layer of sawdust does the trick. Avoid placing the sawdust right near the crowns, as it can form a crust--this crust helps to keep weeds down, but can also inhibit the asparagus from getting water. Another concern is that the microbes that break down sawdust may use up nitrogen; keep an eye out to see if your plants might need a little nitrogen boost during the growing season (turning yellowish or pale green). An alternative mulch would be to use about 4 to 6 inches of straw (not hay).
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