If you’ve ever wondered how does asparagus grow, you’re in the right place. This perennial vegetable has a unique growth process that’s different from most garden crops, and understanding it is key to a successful harvest.
Growing asparagus requires patience but rewards you with delicious spears for decades. Let’s walk through the entire journey, from planting a crown to harvesting your first spears.
How Does Asparagus Grow
Asparagus doesn’t grow from seeds in your yearly garden. Instead, it grows from underground crowns, which are the root systems of one-year-old plants. These crowns send up edible shoots, called spears, each spring. If a spear is left unharvested, it develops into a tall, fern-like plant that photosynthesizes and feeds the crown for next year’s crop.
Starting Your Asparagus Bed: Site and Soil
Choosing the right location is crucial because your asparagus bed will be productive for 15 years or more. Asparagus needs full sun—at least 8 hours a day. The soil must be well-draining; soggy roots will cause the crowns to rot.
Prepare the soil deeply. These roots grow extensive and deep.
- Dig a trench about 12 inches deep and 12 inches wide.
- Mix compost or well-rotted manure into the excavated soil.
- Aim for a soil pH between 6.5 and 7.0. A simple test kit can check this.
Planting the Crowns: A Step-by-Step Guide
It’s best to plant one-year-old crowns from a reputable nursery in early spring. Here is the proven method for planting.
- Create a small mound of soil down the center of your prepared trench, about 2-3 inches high.
- Place the crowns on top of the mound, spacing them 12 to 18 inches apart. Let the roots drape down the sides of the mound.
- Cover the crowns with just 2-3 inches of your amended soil. Do not fill the trench completely yet.
- Water the planted crowns thoroughly.
The First Critical Growing Season
As the plants begin to grow, you’ll see thin spears emerge. Do not harvest any spears in this first year. The plant needs all its energy to establish a strong root system.
As the ferns grow, gradually backfill the trench with more soil until it’s level by the end of the season. Keep the bed well-weeded, as asparagus doesn’t compete well. Water consistently, providing about 1-2 inches per week.
The Second Year and Patience
In the second spring, you will see more and thicker spears appear. You can enjoy a very light harvest—cut spears for about 2 to 3 weeks only. Then, allow the rest to grow into ferns. This extended growing period continues to build the plant’s energy reserves.
By the third year, your patience pays off. You can harvest spears for a full season, which typically lasts 6 to 8 weeks.
The Annual Growth Cycle of an Established Plant
Once mature, asparagus follows a reliable annual cycle. Here’s what happens each year:
- Spring Harvest: As soil temperatures reach about 50°F, spears push up from the crown. You harvest these when they are 6 to 10 inches tall.
- Fern Growth: After the harvest period ends, you stop cutting. The remaining spears grow unfettered into tall, feathery ferns.
- Energy Storage: All summer, these ferns capture sunlight and send energy down to the crown, storing it for next spring’s crop.
- Dormancy: In the fall, the ferns turn yellow and brown. You cut them back to the ground after a hard frost to prevent pest issues.
How to Harvest Correctly
Proper harvesting technique protects the crown and ensures future yields. Use a sharp asparagus knife or a small serrated knife.
- Harvest spears when they are about as thick as your pinky finger and 6 to 10 inches tall.
- Cut the spear at a slight angle, about 1 to 2 inches below the soil surface. Be careful not to damage nearby emerging spears.
- Harvest every day or every other day during the season, as spears grow incredibly fast in warm weather.
Common Problems and Simple Solutions
Asparagus is generally low-maintenance, but a few issues can arise.
Asparagus Beetles
These black and red beetles and their larvae chew on ferns and spears. Hand-pick them off and drop them in soapy water. Keeping the bed clean in fall helps reduce their overwintering spots.
Rust Disease
This fungal disease causes orange spots on the ferns. It’s less common with resistant varieties like ‘Jersey Knight’ or ‘Jersey Giant’. Ensure good air circulation and avoid wetting the foliage when watering.
Weak or Thin Spears
This is usually a sign the plant is either too young to harvest fully, needs more nutrients, or is getting overcrowded. Ensure you are fertilizing in early spring and side-dressing with compost after the harvest ends.
Winter Care and Long-Term Maintenance
After cutting back the dead ferns in late fall, apply a thick layer of compost or well-rotted manure over the bed as a winter mulch. This protects the crowns and feeds the soil as it breaks down. Every few years, you can divide very old, crowded crowns in early spring before growth starts, but this is often not necessary for many years.
FAQ About Growing Asparagus
How long does it take to grow asparagus?
From planting crowns, it takes about 3 years for a full harvest. The first two years are for plant establishment.
Can you grow asparagus from seed?
Yes, but it adds an extra year to the timeline. Seeds are started indoors and grown for a full year to produce a crown suitable for transplanting.
How much asparagus do you get from one plant?
A single mature crown can produce about 1/2 pound of spears per season over its 6-8 week harvest period.
When should you stop harvesting asparagus?
Stop harvesting when the spears that emerge are thinner than a pencil. This signals the crown’s energy reserves are getting low and it’s time to let it grow ferns.
Does asparagus need a lot of water?
It has deep roots but benefits from consistent moisture, especially during spear production and fern growth. Aim for 1-2 inches of water per week from rainfall or irrigation.
Starting an asparagus bed is a commitment, but the reward of fresh, homegrown spears every spring for years to come is well worth the wait. By following these steps and understanding it’s unique growth cycle, you’ll be set for success.