Planting, Growing, and Harvesting Asparagus
Planting, Growing, and Harvesting Asparagus
Asparagus is one of the first plants that greets us in springtime. It’s a perennial, which means that once it gets established, asparagus will return year after year. Early spring is the time to plant asparagus, so what are you waiting for?
Note: Asparagus plants may take 2 to 3 years to truly get started and produce, so patience is needed! But then again, the plant can be productive for 20 years or more, producing ½ pound of spears per foot of row in spring and early summer, so we think it’s worth the wait.
Asparagus are dioecious, which means that there are male and female plants. The key to the sex of the plant appears in the fall: Red berries form on female ferns. Inside the berries are tiny seeds—about 19,200 to a pound—and, yes, you can plant them—although it will take at least 3 years before you have a harvestable crop. Because male plants do not need to expend energy in producing berries, they have stronger root systems and can be up to three times more productive than female plants.
Regions with cool winters are best for this cool-season crop, which is planted in early spring.
Preparing for Planting
- Asparagus is planted in early spring as soon as the soil can be worked.
- The plant is normally grown from “crowns” (1-year-old plants).
- Before you do anything, check the pH of your soil. Asparagus likes a pH of 6.0 to 8.0.
- Asparagus does not like to have its feet “wet,” so be sure that your garden bed has good drainage. (For that reason, raised beds can be a good place to plant asparagus. Learn how to make a raised garden bed.)
- Eliminate all weeds from the bed, digging it over and working in a 2- to 4-inch layer of compost, manure or soil mix. (Learn more about soil amendments and preparing soil for planting.)
How to Plant Asparagus
- Plant crowns deeply to protect them from the deep cultivation needed for annual weed control.
- Dig a trench of 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.
- Within the trench, space asparagus crowns 12 to 18 inches apart (measured from root tip to root tip).
- The traditional method of planting asparagus goes as follows:
- Add a 2-inch-high mound of rich soil to the bottom of the trench and place the asparagus crowns on top of the mound, spreading their roots out evenly.
- Add about 2 inches of soil over top of the crowns.
- As the season progresses and spears grow to be 2–3 inches tall, add 2 more inches of soil, 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 one or two 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.
- Rather than fill in the trench little by little, some gardeners prefer to fill it in all at once. While it’s thought that the traditional method results in stronger plants overall, gardeners don’t typically have any issues result 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:
How to Grow Asparagus
- When the trench is filled, add a 4- to 6-inch layer of mulch and water regularly.
- Do not harvest the spears in the first year (the plant needs time to grow out its root system), but cut down dead foliage in late fall and side-dress with compost.
- During the second year, harvest for only 3 to 4 weeks, side-dressing in spring and early fall and cutting down dead foliage in late fall.
- During the third year, the bed should be in full production, so you can start to harvest asparagus sparingly throughout the season.
How to Harvest Asparagus
- If you have young plants, the season may last 2 to 3 weeks. However, established plants produce longer—up to 8 weeks.
- Asparagus can take three growing seasons to harvest, though you may be able to lightly harvest during the second year.
- 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 have foliage, it’s too tough for eating.
- Harvest spears at 6 to 8 inches tall and at least ½ inch thick, cutting the spears off with a knife or scissors at the soil line.
- Stop harvesting spears when the diameter of the spears decreases to the size of a pencil.
- After harvest, allow the ferns to grow; this replenishes the nutrients for next year’s spear production. Always leave one or two spears.
- Cut back asparagus AFTER the foliage has died back and turned brown or yellow. This is usually in the fall after frost. Cut back to the ground.
How to Store Asparagus
- Asparagus does not keep for very long after it’s picked, so be sure to eat it within two or three days from harvest.
- Brush off any visible dirt or give the spears a light washing with cold water before storing. It’s very important to dry washed spears thoroughly; moisture can lead to mold.
- 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.
- For highest yields, plant male hybrids such as ‘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.
- 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.