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Asparagus – Growing Guide

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Overview

Description

Asparagus is a perennial plant cultivated for its young shoots, known as spears, which are consumed as a vegetable. Once established, asparagus can produce for over 15 years. The plant features tall, feathery, fern-like foliage growing from a crown that resides below the soil surface. The crown consists of a mass of rhizomes (underground stems) and roots.

In spring, the plant sends up shoots, known as asparagus spears, from the crown. These spears can grow 100-150 cm (40-60 in) tall. After the harvest period, the spears expand to produce feathery foliage, which captures sunlight to generate energy. This energy nourishes the crown, enabling it to produce new shoots for the next season.

Asparagus plants produce small, bell-shaped flowers that are typically yellow-green in color. These flowers become small, round berries, which are red when ripe. Each berry usually contains around 3-6 seeds, that can be used for propagation.

Interesting Facts

  1. Asparagus can take three years from seed to first harvest.
  2. The spears grow from the crown underground, which can live and produce for up to 20 years.
  3. Asparagus spears can grow up to 25cm (10 in) in a single day under ideal conditions. This rapid growth is one reason why asparagus needs to be harvested frequently during its growing season.
  4. White asparagus is created by earthing up soil around the spears to block sunlight and prevent photosynthesis.
  5. Asparagus is a natural diuretic due to its high concentration of the amino acid asparagine.
  6. It was prized by the ancient Greeks and Romans for its flavor and supposed medicinal properties.

Interesting Fact About Asparagus and Urine Smell

An interesting fact about asparagus is that it can cause a distinctive smell in urine shortly after consumption. This phenomenon occurs because asparagus contains a unique sulfur compound called asparagusic acid. When the body digests asparagus, it breaks down this compound into volatile sulfur-containing byproducts, such as methanethiol and dimethyl sulfide. These byproducts are then excreted in the urine, leading to the characteristic odor.

Interestingly, not everyone can detect this smell. The ability to smell the compounds is genetic, meaning some people produce the odor but cannot smell it, while others can both produce and smell it, and some may not produce it at all. This unique interaction between asparagus and human physiology adds a quirky twist to this already fascinating vegetable.

Basic Growing Information

Asparagus is generally considered a cool-season crop that thrives in cooler weather. It is typically planted in early spring when young spears begin to emerge as temperatures rise. Despite its early growth in spring, asparagus is well-suited to cooler climates. After the spears are harvested, the plant develops feathery foliage that helps store energy for the next growing season, allowing it to tolerate a range of temperatures throughout the year.

Asparagus grows best in regions with warm days and cool nights. It requires a period of cold temperatures to break dormancy and ensure a healthy growth cycle. Typically, asparagus needs about 500-1000 cumulative chilling hours at temperatures below 7°C (45°F) to break dormancy effectively.

For optimal growth, asparagus should be planted in a sunny location in the home garden to maximize sunlight exposure. It is important to avoid low-lying areas, as a late frost can damage newly emerged spears, reducing the quality and yield of the crop. Choosing well-drained soil and the proper site can help prevent frost damage and promote healthy plant growth.

Planting

Note: Check gardening calendars for the best planting times in your location

In the following section are step-by-step instructions for how to grow asparagus from seed, and how to grow asparagus from one year old crowns using the mounding or trench methods for planting.

1. How to Grow Asparagus from Seed

Growing asparagus from seed is a rewarding process that requires patience, as it typically takes three years from seed to the first harvest. Begin by sowing seeds indoors about 12 to 14 weeks before the last expected frost date. Use seed trays or small pots filled with a high-quality seed-starting mix. Sow the seeds about 1 cm (0.5 in) deep, and keep the soil consistently moist but not waterlogged. Place the trays in a warm location with temperatures around 21-24°C (70-75°F). Germination usually takes 2 to 3 weeks.

Once the seedlings have grown to a height of 15-20 cm (6-8 in) and have developed a few sets of true leaves, they are ready to be transplanted into the garden. Choose a sunny location with well-drained soil. Prepare the planting bed by digging trenches about 30cm (12 in) wide and 15 cm (6 in) deep. Amend the soil with compost or well-rotted manure to provide a nutrient-rich environment.

Before transplanting, harden off the seedlings by gradually exposing them to outdoor conditions over a week. Space the seedlings about 30-45 cm (12-18 in) apart in the trenches. Place the seedlings in the trench, spreading the roots out gently. Cover the roots with 5-7 cm (2-3 in) of soil, and water thoroughly. As the plants grow, gradually fill in the trench with soil until it is level with the surrounding ground.

Asparagus requires consistent care, including regular watering, weeding, and mulching to conserve moisture and suppress weeds. With patience and proper care, your asparagus plants will establish strong root systems and produce spears in their third year and for many more after that.

2. How to Plant Asparagus Crowns Using the Mounding Method

Planting asparagus crowns is a popular method to establish an asparagus bed, offering a quicker route to harvest compared to growing from seed. Crowns are the dormant roots of one-year-old asparagus plants and can produce spears as early as the following spring.

Here’s a step-by-step guide on how to plant asparagus crowns in the ground using the mounding method, which involves digging individual holes and creating a mound in the center of each hole to elevate the crown. This approach ensures that the roots are well-distributed and the crowns are properly positioned for optimal growth. Here’s how to do it:

  1. Site Selection: Choose a sunny location with well-drained soil. Asparagus prefers full sun and rich, fertile soil. Avoid areas prone to waterlogging or late frost, which can harm the plants. Asparagus crowns can be planted once the soil can be worked and soil temperatures have warmed up to 10°C (50°F).
  2. Soil Preparation: Prepare the planting area by removing weeds and debris. Amend the soil with plenty of organic matter, such as compost or well-rotted manure, to enhance fertility and drainage.
  3. Digging Holes: Dig individual holes for each crown. The holes should be about 30cm (12 in) wide and 15-20cm (6-8 in) deep. Space the holes 30-45cm (12-18 in) apart in rows that are 100-120 cm (3-4 ft) apart to give the plants plenty of room to grow.
  4. Creating the Mound: In the center of each hole, create a mound of soil high enough so that when the crown is placed on top, the top of the crown will be just below the soil surface. This ensures that the roots are spread out evenly around the mound.
  5. Placing the Crowns: Position each asparagus crown on top of the mound, spreading the roots evenly around it. The crowns can be placed with either side up, and will still grow, but if the roots clearly hang downwards, or buds are visible at the top of the crown, then place them with the top facing upwards. The crown should sit just below the soil surface.
  6. Covering the Crowns: Cover the crowns with soil, ensuring that the tips are just below the soil surface. Water the newly planted crowns thoroughly to help settle the soil around the roots.
  7. Mulching and Care: Apply a layer of mulch to conserve moisture, suppress weeds, and maintain soil temperature. Water the asparagus bed regularly, keeping the soil consistently moist but not waterlogged. Weed the area regularly to reduce competition for nutrients.
  8. Fertilizing: Feed the asparagus bed with a balanced fertilizer in early spring and after the harvest season to help the plants build energy reserves for the next growing season.
  9. First Harvest: Patience is key when growing asparagus. New spears should start to emerge from the soil within a week of planting. However, avoid harvesting any spears in the first year to allow the plants to establish a strong root system. Allow the spears to grow into ferns and develop, as this helps the asparagus plant gather energy, which is essential for the crown to produce healthy spears in the following year. In the second year, you can harvest lightly for a few weeks. By the third year, the asparagus bed should be well-established, allowing for a full harvest season.

Using this mound method ensures that asparagus crowns are well-supported and encourages healthy root development, leading to vigorous plant growth and abundant harvests.

    3. How to Plant Asparagus Crowns Using the Trench Method

    Another effective method for planting asparagus crowns involves digging trenches and gradually filling them in as the plants grow.

    Here’s a step-by-step guide on how to plant asparagus crowns in the ground using the trench method:

    1. Site Selection: Choose a sunny location with well-drained soil. Asparagus thrives in full sun and rich, fertile soil. Avoid areas prone to waterlogging or late frost, as these can damage the plants. Asparagus crowns can be planted once the soil can be worked and soil temperatures have warmed up to 10°C (50°F).
    2. Soil Preparation: Prepare the planting bed by removing weeds and debris. Dig trenches that are 30cm (12 in) wide and 15-20cm (6-8 in) deep. Amend the soil with plenty of organic matter, such as compost or well-rotted manure, to improve fertility and drainage.
    3. Planting the Crowns: Place the asparagus crowns in the trench, spacing them 12-18 inches apart. Ensure the crowns are positioned with the roots spread out evenly. The crowns can be placed with either side up, and will still grow, but if the roots clearly hang downwards, or buds are visible at the top of the crown, then place them with the top facing upwards. Cover the crowns with 5-7 cm (2-3 in) of soil, leaving the tips just below the soil surface.
    4. Watering and Filling the Trench: Water the newly planted crowns thoroughly to settle the soil around the roots. As the plants grow, gradually fill in the trench with soil, covering the emerging shoots, but taking care not to bury them completely.
    5. Mulching and Care: Apply a layer of mulch to conserve moisture, suppress weeds, and maintain soil temperature. Regularly water the asparagus bed, keeping the soil consistently moist but not waterlogged. Weed the area regularly to reduce competition for nutrients.
    6. Fertilizing: Feed the asparagus bed with a balanced fertilizer in early spring and after the harvest season. This helps the plants build energy reserves for the next growing season.
    7. First Harvest: Patience is key when growing asparagus. New spears should start to emerge from the soil within a week of planting. However, avoid harvesting any spears in the first year to allow the plants to establish a strong root system. Allow the spears to grow into ferns and develop, as this helps the asparagus plant gather energy, which is essential for the crown to produce healthy spears in the following year. In the second year, you can harvest lightly for a few weeks. By the third year, the asparagus bed should be well-established, allowing for a full harvest season.

    With proper care and maintenance, your asparagus crowns will thrive, providing you with delicious spears each spring for many years.

    Care and Maintenance

    Growing Difficulty

    Growing Tips

    Companion Plants

    Common Pests and Diseases

    Harvesting

    Ideal Thickness for Harvesting Asparagus Spears: Tips for Best Flavor and Texture

    When determining which asparagus spears to harvest, it’s important to select spears that are thick enough to ensure they are mature and have developed good flavor and texture. The minimum thickness for harvesting asparagus spears is generally about the diameter of a pencil, which is approximately 0.5 inches (1.3 cm). Spears thinner than this are typically left to grow and develop further, as they are not yet mature enough for optimal taste and texture. Harvesting spears at the right thickness ensures that you get the best quality produce, with tender yet flavorful spears. Additionally, leaving thinner spears to grow allows the plant to build up energy reserves for future production, supporting overall plant health and yield.

    Propagation

    Asparagus crowns can be propagated by dividing crowns in early spring every few years to rejuvenate overcrowded beds.

    This practice can help extend the productive life of the plants. Dividing asparagus crowns rejuvenates the plants and can lead to improved spear production. Here’s more information on the process and timing:

    How to Divide Asparagus Crowns

    1. Timing: Asparagus crowns should generally be divided every 8 to 10 years to rejuvenate the plants and extend their productive life. The best time to divide asparagus crowns is in early spring before new growth begins or in late fall after the foliage has died back.
    2. Preparation: Before dividing the crowns, prepare a new planting area with well-drained soil and plenty of organic matter. Choose a sunny location to maximize growth and spear production.
    3. Digging Up Crowns: Carefully dig up the mature asparagus crowns, taking care not to damage the roots. Use a garden fork or spade to lift the crowns from the soil.
    4. Dividing the Crowns: Using a sharp knife or spade, divide the crowns into sections, ensuring that each section has several healthy buds and an adequate root system. Typically, each divided section should have 2-3 buds and a good amount of roots.
    5. Replanting: Replant the divided crowns immediately in the prepared area. Dig holes or trenches and create mounds as needed. Place the divided sections on the mounds with the buds just below the soil surface, and cover them with soil. Water thoroughly to help settle the soil around the roots.
    6. Care: After replanting, maintain regular care, including watering, mulching, and fertilizing as needed. Avoid harvesting spears from newly divided crowns for the first year to allow the plants to establish strong root systems.

    Benefits of Dividing Crowns

    By dividing asparagus crowns every 8 to 10 years, you can help ensure that your asparagus bed remains productive for longer than the typical 15-20 years, extending its productive life and maintaining healthy, vigorous plants.

    Maximizing Asparagus Yields: Male vs. Female Plants and What Gardeners Need to Know

    Gardeners are often advised to seek male asparagus plants for their gardens, but many may be unsure of the reason why. Understanding the differences between male and female asparagus plants can shed light on this recommendation and help gardeners make better informed decisions about asparagus growing.

    Asparagus plants are dioecious, meaning they have separate male and female plants. Male plants produce only spears, while female plants produce both spears and seeds (berries). This distinction can impact the productivity and maintenance of an asparagus bed.

    Male Plants: Male asparagus plants are often preferred by gardeners because they are more productive. Since male plants do not expend energy on producing seeds, they typically yield more spears. Additionally, the absence of berries reduces the chances of volunteer seedlings, which can compete with established plants for nutrients and space.

    Female Plants: Female asparagus plants produce fewer spears because some of their energy is diverted to seed production. The berries that form on female plants can drop and lead to unwanted seedlings in the asparagus bed, which may require extra maintenance to manage.

    Relevance to Gardeners: For home gardeners, understanding the difference between male and female asparagus plants can help in selecting the best varieties for higher yield and easier maintenance. Many modern asparagus varieties are predominantly male or all-male hybrids, bred for their productivity and lack of seed production. When planting asparagus, gardeners might choose these all-male hybrids to maximize their harvest and minimize the need for thinning out volunteer seedlings.

    What Gardeners Need to Do: If you are planting from crowns, check if they are all-male hybrids. If you are growing from seeds, you might get a mix of male and female plants. In this case, you can identify and remove female plants after a couple of years, once they start producing berries, to maintain a more productive bed. Regular maintenance, such as removing any volunteer seedlings, is also recommended to keep your asparagus bed healthy and productive.

    While growing female asparagus plants in a home garden is not inherently problematic, male plants offer advantages in terms of yield and maintenance. However, female asparagus plants still produce delicious spears and can be a valuable part of a home garden. The primary difference lies in the slightly lower yield and the need for occasional weeding of volunteer seedlings, which are essentially free plants which can be transplanted elsewhere. For many home gardeners, these factors may not pose significant issues, especially if they are prepared to do a bit of extra maintenance.

    Culinary Uses

    Asparagus is a versatile vegetable that can be prepared in numerous ways, making it a staple in kitchens worldwide. It can be steamed, boiled, grilled, roasted, or even eaten raw, depending on the desired texture and flavor profile.

    Steaming and Boiling: Steaming or boiling asparagus helps retain its vibrant green color and tender-crisp texture. These methods are particularly popular for preparing asparagus as a simple side dish, often dressed with a drizzle of olive oil, a squeeze of lemon, or a sprinkle of salt and pepper. For an extra layer of flavor, the vegetable can be tossed with garlic, herbs, or Parmesan cheese.

    Grilling: Grilling asparagus imparts a smoky flavor and slightly charred edges that contrast beautifully with its natural sweetness. Before grilling, it’s common to brush the spears with olive oil and season them with salt, pepper, and perhaps a hint of balsamic vinegar. Grilled asparagus pairs well with grilled meats and fish or can be added to salads and grain bowls.

    Roasting: Roasting asparagus brings out its natural sugars, resulting in a caramelized exterior and a tender interior. Roasted asparagus can be enhanced with various toppings such as garlic, lemon zest, or crumbled feta cheese. This method is particularly popular in dishes like roasted asparagus and poached egg or asparagus and mushroom risotto.

    Raw: When eaten raw, asparagus has a crisp, fresh flavor that is slightly grassy. Thinly shaved asparagus can be added to salads or used as a garnish for soups and other dishes. It’s often paired with ingredients like shaved Parmesan, lemon, or vinaigrettes to create a refreshing and nutritious dish.

    Gourmet Applications: Asparagus is frequently used in gourmet cooking, where its delicate flavor and elegant appearance are highly valued. A classic example is asparagus wrapped in prosciutto, which is often served as an appetizer. The salty, savory prosciutto complements the earthy, sweet asparagus, creating a dish that’s both simple and sophisticated. Asparagus is also a popular ingredient in quiches, tarts, and pasta dishes, where it can be combined with eggs, cheese, and other vegetables to create a rich and satisfying meal.

    In addition to these traditional methods, asparagus is increasingly being used in innovative ways, such as in smoothies, asparagus pesto, or even pickled asparagus, which adds a tangy, crunchy element to charcuterie boards and sandwiches.

    Overall, asparagus’s versatility in the kitchen makes it an essential ingredient for both everyday meals and special occasions, offering endless possibilities for culinary creativity.

    In conclusion, growing asparagus requires patience but rewards with years of harvests. Properly established and managed asparagus beds are a long-term investment that can provide delicious spears every spring for many years.

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