Asparagus is a perennial vegetable. It takes three years from planting to get an appreciable crop, but the fresh asparagus is well worth the wait. A well-maintained asparagus patch will continue to yield for 15 to 20 years.
Choosing a Bed for Asparagus
Asparagus foliage will grow tall enough to shade any surrounding vegetation, so it is usually grown in a prepared, dedicated bed. A few things to consider when selecting a site for your asparagus bed include:
- Sun: Full, but can thrive in partial sun
- Soil type: Loamy or sandy
- Soil pH: 6.5 ideal, but can live in 7.0
- Height: 4'-5'
- Spread: 3'-4'
- US Hardiness Zones: Zones 3-8
Other things to consider for an ideal asparagus bed location include:
- Asparagus doesn't compete well with other plants, so the bed should be dedicated only to growing asparagus.
- The plot should not be subjected to digging or tilling.
- Asparagus should be planted 12" to 18" apart.
- Plan around 12-15 plants per person when selecting your garden spot.
- Select a spot in your garden where the ferns won't block out the sun for other plants.
- Each plant can yield 10 to 20 spears, so choose a plot that is spacious enough for this type of yield.
- Keep watered but don't over water since asparagus doesn't have wet feet. A slow drip irrigation system is ideal for an asparagus bed.
Preparing the Bed
Since asparagus plants live so long, it is important to prepare the plot before you plant. Asparagus thrives in rich, well-drained, organic soil.
Option to Plant Cover Crop
Many gardeners start an asparagus bed by planting a cover of green manures. These are plants grown for the sole purpose of turning them under to provide mulch for the asparagus bed. Once the cover crop is mature, you need to turn them under. After this stage, you can begin preparing the asparagus bed for planting:
- Remove all weeds and grass. Asparagus will falter if the bed has weeds and/or grass.
- Till the ground to a depth of 12 inches.
- Place three inches of compost over that and till to mix it thoroughly with the dirt.
- Finally, till in the fertilizer. A mixture of 10-20-10 applied at the rate of two to three pounds per 20-foot row is usually recommended.
Choose Either Seed or Crown Asparagus to Plant
You can either buy asparagus seeds or crowns to plant. It's far easier to grow asparagus from crowns than to grow using seeds. Most gardeners opt to buy bundles of roots, called crowns.
How to Buy Asparagus Crowns
Asparagus crowns are available in the spring. There are a few things to keep in mind when you shop for asparagus crowns. For example, new hybrid asparagus varieties provide only male asparagus since these produce more asparagus than female asparagus. Some gardeners prefer to plant heirlooms. Should you opt for an heirloom asparagus, you'll receive male and female asparagus crowns.
Things to consider when buying asparagus crowns include:
- Purchase one-year-old crowns.
- Buy bundles of 10 to 25 crowns, with firm, fresh roots.
- When purchasing male crowns, check the label or description to ascertain if the mix is all male or a mix of male and female plants. If the mix isn't evident move on to another choice until you find what you want.
- Choose a variety recommended your zone (information on packaging or web).
How to Plant Asparagus Crowns
Asparagus should be planted in the spring as soon as the ground thaws. However, gardeners in the southern region of the United States often store the crowns in the refrigerator until the summer heat has passed. The crowns are then planted in early fall as soon as the temperatures drop. If you store the dormant crowns in the refrigerator, make sure you keep the roots moist with damp paper towels. Is you live in a cooler region, you can store in a paper bag and fill it with sawdust, storing in a cool place like a root cellar.
A few simple steps for planting dormant asparagus crowns include:
- Dig a trench that is 6"-18" deep and 4" wide.
- If planting more than one trench, space 4' apart to allow enough space for the plants to grow.
- Using mulch, soil and compost create a 3"-4" mound along the center length of the trench.
- Place each crown on this center mound being careful to spread the roots out and allow to cascade over the mound.
- Space the crown 12"-18" apart.
Add compost and soil around the crowns leaving 2"-3" of shoots above ground.
As the shoots grow from the crown, continue filling in the trench so that the shoots just barely peak through the dirt, about 2"-3" high.
You'll continue this process until the trench is completely filled.
Keep the soil along the center of the trench mounded so the water properly drains.
Tips for Fall and Spring Plantings
A few helpful tips for planting asparagus crowns in the fall and spring ensure your crop survives. Take these precautions for a healthy growth.
- If planting in the spring, the trench should be filled in by the end of the first year.
- Fall plantings are best served by filling in the trench once the crowns are planted. The shoots will emerge through the soil without any problems.
- Many gardeners planting in the spring prefer to fill in the trench at one time. This method is acceptable and won't harm the crowns.
Caring for Your Asparagus Crown Plants
The first three years of growing asparagus requires a bit of patience. It's possible to start harvesting a few spears the second year.
During the first year, do not cut the asparagus shoots. They need to grow into asparagus ferns to feed the roots so they can survive the first winter. Water the plants weekly, giving them 1" of water each time. When winter comes and the asparagus ferns die, cut them back to about 1" above ground.
- Discard all cut vegetation to prevent the spread of the asparagus beetle.
- After cutting the ferns from the asparagus, spread three inches of compost on the asparagus bed.
- Fertilize with a mixture of 10-20-10 fertilizer at the rate of two to three pounds per 20 feet of row.
When new shoots emerge in the spring, you can cut the ones that are thicker than your finger. As soon as the shoots become smaller than this, quit cutting them. Allow the shoots become ferns and grow until winter, when you'll cut them back to the ground. Continue to water weekly, giving the plants one inch of water each time.
Year Three and Beyond
Treat the asparagus bed the same as you did in year two. You can harvest asparagus shoots until they become as thin as a pencil, about six to eight weeks each year.
- When the stalks become as thin as a pencil, allow them to grow asparagus ferns.
- Continue to water weekly, giving them 1" of water each time.
- Each winter, cut back the ferns to about 1" above ground.
- Keep plants mulched to retain moisture.
Growing Asparagus From Seeds
Growing asparagus from seeds is more economical than purchasing dormant asparagus crowns. You will need to start the seeds indoors about 14 weeks prior to transplanting outdoors. Depending on your region, you may transplant the asparagus in the spring or early fall.
- Soak seeds for 2-4 hours.
- Use sterile seeding mix for growing medium.
- Plant seeds ½"deep in 2" peat pots or a deep planting tray.
- Use a grow light, but allow plants total darkness for 8 hours out of every 24 hours.
- Seeds will germinate between 2-3 weeks.
- Keep soil temperature around 70°F-80°F (use a seedling heat mat).
- Acclimate plants for one week prior to transplanting.
- Transplant in prepared asparagus bed spacing 12"-18" apart.
Transplant Asparagus Seedlings Into Temporary Bed
Another practice for asparagus grown from seed is to use a temporary transplant bed for the first year (prepared like final bed). You'll transplant the seedlings 6" apart.
At the beginning of the first-year fall, you'll transplant the asparagus seedlings into the final growing bed, spacing the plants 18" apart. If your first transplant is in the fall, you'll wait until the following fall to move the seedlings into the final grow bed. Set the plants 18" apart just as you would asparagus crowns.
Care and Maintenance of Asparagus Grown From Seeds
The care and maintenance of asparagus grown from seeds is the same as those grown from crowns. Keep plants mulched, weeded, fertilized, and watered. Begin harvesting in the third year.
How to Harvest Asparagus
It's easy to harvest asparagus. Once the spears begin to grow, you should be able to harvest every 3-4 days. As temperatures climb, some gardeners find their harvesting requires daily or even twice daily.
- You will harvest the spears whenever they reach 8"-12" tall.
- You want to harvest spears while the tips are firm. Tips that are unfurling are too old to harvest.
- You can cut the spears at ground level using a knife.
- Some gardeners prefer to snap the stalks by hand at ground level.
Harvesting Guidelines for Years One, Two and Three
Most gardeners refrain from harvesting asparagus during the first two or three years. This allows the asparagus tips to open and grow what's called ferns. The ferns nourish the root system in preparation for next year's crop.
- While you can harvest a few spears the first year, limit harvesting to one week only.
- The second year, you can harvest spears for up to two weeks.
- On the third year, you should limit harvest time to three to four weeks.
- After the third year, you're free to harvest spears.
- Stop harvesting when the spears decrease in diameter and resemble pencil sizes.
How to Divide Asparagus Plants
Over the years, the production of your asparagus plants can slow down. This is an opportune time to divide the asparagus crowns and transplant into a new bed. A few easy steps can reap more asparagus next year.
- Once you've cut back the ferns in the fall, dig up the roots you wish to divide.
- Cut the shoots into crowns so each has attached roots.
- Plant the divided crowns in the new bed.
- Allow the divided plants one year to reestablish their root systems.
- You can start to harvest the asparagus in the second year.
The major problem for most asparagus beds is weeds. Since you should not hoe or rake around the asparagus plants, the only solution is to pull weeds by hand. If you don't pull weeds growing among the asparagus, the weeds can either take over the bed, and dominate the asparagus or sap vital nutrients from the plants.
Tall Asparagus Fern-Like Fronds
The tall, fern-like fronds are actually produced by the asparagus plants themselves, so don't mistake them for weeds. The frothy plume-like foliage produces food for the plant each year and is vital to its health and success.
Asparagus officinalis has several varieties you can consider growing. The main differences besides appearance is the taste.
- You can choose a pink tipped asparagus variety.
- The most common and traditional asparagus variety is green.
- White asparagus has no color as the result of cultivating. The plants are always underground. The lack of sun for photosynthesis gives the spears a white color.
Easy Steps for How to Grow Asparagus
Asparagus takes a little patience in the beginning, but you'll be rewarded with the harvest you get for many years. For best results, maintain the asparagus bed with proper weeding, fertilizing, mulching, and watering.