Asparagus is a unique perennial vegetable that can remain productive for 15 to 30 years with proper care. This extended lifespan makes the initial preparation and placement of the bed extremely important, as the location cannot be easily changed once the plants are established. Long-term success is determined by the conditions given at the beginning, specifically the preparation of the soil and the precise spacing of the crowns.
Preparing the Planting Site
Because asparagus beds are permanent, the planting site must be chosen and prepared meticulously. Asparagus thrives in full sunlight, needing a minimum of eight hours of direct sun exposure daily. The soil must be deep and exceptionally well-drained, ideally a sandy loam texture, as the root system can extend several feet deep and wide.
Preparing the soil involves amending it to a depth of at least 12 to 18 inches to accommodate extensive root growth. Incorporating plenty of organic matter, such as aged compost or manure, helps loosen the soil structure and improve drainage and fertility. The soil pH should be slightly acidic to neutral, ideally ranging from 6.5 to 7.5.
A crucial step is the complete removal of all perennial weeds, such as bindweed or quackgrass, before planting. Once crowns are in the ground, their dense root structure makes it nearly impossible to remove aggressive weeds without damaging the crop. This pre-emptive control prevents competition for water and nutrients, which is detrimental to young, establishing crowns.
Optimal Spacing and Depth Requirements
Asparagus crowns are typically planted in a deep furrow or trench to encourage deep root establishment. The trench should be 12 to 18 inches wide and 6 to 12 inches deep, adjusted based on soil type. Use a shallower depth (6 to 8 inches) for heavy clay soils, and a deeper trench (8 to 12 inches) for sandy soils. At the bottom, form a small mound or ridge of soil, about 4 to 6 inches high, to serve as the base for the crown.
The individual crowns are placed atop this mound, with the fleshy roots carefully spread out to drape down both sides. The distance between these crowns, known as in-row spacing, should be 12 to 18 inches apart. This generous spacing allows mature root systems adequate room to expand without competing intensely for soil resources and moisture.
Row spacing, the distance between separate trenches, is generally set at 4 to 5 feet apart. This wide separation accommodates the above-ground growth of the ferns that develop later in the season, not the underground roots. Proper row spacing ensures good air circulation for disease prevention and allows sufficient sunlight to reach the foliage for maximum energy production.
First-Year Care and Establishment
Immediately after planting the crowns on the soil mounds, cover them lightly with only two to three inches of soil, leaving the rest of the trench open. As new spears emerge and grow taller throughout the first season, gradually fill the trench in stages with the remaining soil. This slow backfilling ensures the crown is buried at the correct depth while preventing the young shoots from being smothered.
Consistent moisture is important for newly planted crowns to establish root systems, but the soil must never be waterlogged. Watering should be deep and infrequent, aiming to provide at least one inch of water per week, especially during dry periods. Allowing the young plants to dry out can severely inhibit their growth.
Maintaining a weed-free environment is paramount during the first year, as young asparagus plants cannot compete with aggressive weeds. Hand-weeding is the preferred method, taking caution to avoid damaging the shallowly covered crowns and emerging spears. Shallow hoeing can be done, but it must not penetrate more than an inch or two into the soil to prevent root damage.
The most important rule for first-year care is strict adherence to the no-harvest rule: no spears should be cut or eaten during the entire first growing season. This period is dedicated to building the plant’s energy reserves, so all emerging spears must be allowed to grow into tall, feathery ferns. These ferns photosynthesize and store carbohydrates in the underground crown to support future production. A second year of very light harvesting is often recommended to ensure the plant develops a robust root system that can support decades of successful harvests.