How to Plant, Grow, and Harvest Asparagus

Begin growing asparagus indoors if your climate is cold, about three months before spring planting. To help seeds sprout faster, soak them in water for a few hours before planting. Use a pot filled with potting mix, sprinkle the seeds, and cover them lightly with soil. Once the weather warms up, you can transplant the seedlings outside. Keep the seedlings under grow lights from the moment they sprout to ensure they don't stretch out in search of sunlight.

About 10 days before you plan to move them outside, start hardening off the seedlings. This means gradually introducing them to outdoor conditions, starting with an hour of sun on the first day and increasing the time each day.

Asparagus prefers well-draining soil with a pH of around 7. Mixing in compost provides extra nutrients that help the plants thrive. Avoid planting asparagus in areas prone to frost or where annual plants might disturb its roots, as these conditions can hinder its growth. Conducting a soil test can help ensure the pH and nutrient levels are just right for asparagus. If the soil is too acidic or lacks essential nutrients, the plants may not grow as well. Adding lime can help raise the soil pH, while compost or organic matter can improve nutrient content and soil structure.

Most gardeners plant asparagus crowns instead of seeds because crowns are established more quickly. Crowns are one-year-old roots with buds ready to grow. Before planting, soak the crowns in water for at least half an hour to help them rehydrate and start growing.

Plant them in a trench that’s 12-18 inches wide and 6-8 inches deep, spacing the crowns 12-18 inches apart within the trench and leaving 3 feet between each trench. Initially, cover the crowns with 2-3 inches of soil, then gradually fill the trench as the spears grow. This method encourages strong root development and healthier plants.

Asparagus needs a sunny spot with at least seven hours of direct sunlight daily. Adequate sunlight ensures the plants can photosynthesize and grow strong, healthy spears. Plant asparagus at the north end of your garden to avoid shading other plants, which could reduce their growth.

If you have limited space, consider growing asparagus in a dedicated bed where it won’t compete for light with other vegetables. The tall, fern-like foliage of asparagus can provide a beautiful backdrop for other garden plants, making it both functional and decorative.

Asparagus thrives in USDA zones three to eight, making it suitable for a wide range of climates. In Northern regions, plant the crowns deeper to protect them from winter cold. Deeper planting helps insulate the roots and crowns, ensuring they survive the cold months. Ensure the planting site is free from frost exposure to help the plants survive through the seasons.

In warmer regions, you might need to provide some shade during the hottest part of the day to prevent the soil from drying out too quickly and stressing the plants.

During the first year, asparagus needs about one inch of water each week to establish strong roots. Depending on your soil type, you may need to adjust the watering frequency. For example, clay soil holds moisture longer, so it needs less frequent watering, while sandy soil may require more frequent watering.

Avoid watering the foliage to prevent diseases and use ground-level or drip irrigation instead. Drip irrigation is particularly effective because it delivers water directly to the roots, reducing the risk of fungal diseases caused by wet foliage.

Water the asparagus deeply if there hasn’t been any rain in the past week to ensure the soil remains consistently moist. Mulching helps retain moisture and prevent soilborne diseases by keeping the soil cool and reducing water evaporation. Be careful to avoid getting the foliage wet, which can lead to disease problems like rust and fusarium. Regularly check the plants for signs of pests or disease, and remove any affected foliage promptly to prevent the spread of problems.

A soil test can tell you what kind of fertilizer to use, ensuring your asparagus gets the right nutrients. If you don’t do a soil test, a 10-10-10 fertilizer ratio is a good option for balanced nutrition. Apply fertilizer in the fall before planting, during planting, and after harvesting to support the plants throughout their growing season.

Regularly adding well-rotted manure, compost, or fish emulsion can also help keep the soil fertile. These organic amendments improve soil structure and provide a steady release of nutrients.

In cooler climates, leave the dead foliage over winter to capture snow, which helps protect the crowns by providing insulation. In late March or late fall in milder climates, cut the plants back to the soil surface to encourage new growth. Pruning helps maintain plant health and vigor by removing old, diseased, or damaged foliage. It also reduces the risk of fungal diseases by improving air circulation around the plants.

Make sure to use clean, sharp tools to avoid introducing pathogens to the plants.

Weeds can compete with asparagus for nutrients, so gently hand-pull weeds to avoid disturbing the asparagus roots. Using mulch can also help retain moisture and reduce weed growth by blocking light from reaching weed seeds. Organic mulches like straw, leaves, or grass clippings are excellent choices because they break down over time, adding nutrients to the soil.

Regularly check for weeds and remove them promptly to prevent them from becoming established and difficult to control.

You can start harvesting asparagus lightly in the second year and more robustly in the third year. Pick spears when they are at least six inches tall, and stop harvesting when the spears become thinner than a pencil. This gradual increase in harvesting allows the plants to establish themselves fully.

Overharvesting young plants can weaken them and reduce their long-term productivity. By the third year, you can enjoy a full harvest season, picking spears regularly for up to eight weeks.

To harvest asparagus, twist and pull the spears by hand or cut them at the soil level with a sharp knife. Snapping spears near the base helps collect the most tender part of the plant, leaving the tougher, woody part behind. Harvesting regularly encourages the plants to produce more spears, but avoid overharvesting to ensure the plants remain healthy.

If you notice that the spears are becoming thin, stop harvesting to allow the plants to recover and build up energy for the next season.

You can divide asparagus crowns in spring or fall to propagate new plants or rejuvenate old ones. Dig under the plant to lift it out, then pull the roots apart to create sections with two shoots each. These sections can be planted in prepared beds to expand your asparagus patch.

Dividing crowns helps maintain plant vigor and productivity by reducing overcrowding and ensuring each plant has enough space to grow. It’s a great way to share plants with friends or expand your garden without buying new crowns.

Asparagus can suffer from diseases like rust, fusarium root and crown rot, and Stemphylium purple spot. Choosing disease-resistant varieties such as Jersey Knight and Jersey Giant can help prevent these issues. Practicing crop rotation and using organic fungicides can also prevent disease.

Crop rotation involves changing the planting location each season to reduce the buildup of pathogens in the soil. Proper sanitation, such as removing diseased plant material and using clean tools, also helps keep diseases at bay.

Asparagus beetles, both common and spotted varieties, can damage spears and ferns. Look for beetles in May and use hand-picking or spraying to manage them. Aphids, cutworms, and Japanese beetles are other common pests. Use organic methods like row covers and insecticidal soap to control them. Regularly inspect your plants for signs of pest damage, such as chewed leaves or distorted growth, and take action quickly to prevent infestations from spreading.

Asparagus adds visual interest to your garden with its tall, straight growth and feathery foliage. Plant it at the north end of the garden to prevent it from shading other plants. While female plants produce attractive red berries, male plants are preferred for higher yields because they don't expend energy on berry production. The tall, fern-like foliage can create a beautiful backdrop for other garden plants and provide vertical interest in your garden design.

There are many varieties of asparagus, each with unique qualities. Erasmus is an all-male purple variety known for its sweet flavor and tender texture. Guelph Millenium is cold-tolerant and high-yielding, making it ideal for northern regions. Jersey Giant is cold-tolerant and rust-resistant, while Jersey Knight is more tolerant to fusarium, making it a reliable choice for most climates. Other popular varieties include Jersey Supreme, Mary Washington Improved, Pacific Purple, Purple Passion, and Spartacus, each offering different advantages for gardeners.

Growing asparagus is a rewarding project for any home gardener. With proper planting, care, and patience, you can enjoy this nutritious vegetable for many years. Follow these steps to ensure a bountiful and healthy asparagus harvest, and you'll be able to savor the fresh taste of home-grown asparagus each spring. Whether you're a seasoned gardener or just starting, asparagus is a valuable addition to your garden that will continue to produce delicious spears year after year.