Asparagus is a rewarding, long-term garden investment, capable of producing for 20 years or more. Because this perennial crop occupies the same space for decades, success depends entirely on proper initial establishment. Understanding the precise timing and preparation required is fundamental to ensuring the crowns develop the robust root system necessary for generous harvests. This guide details the steps for successfully planting asparagus, focusing on the preparation and mechanics that lead to a thriving, permanent patch.
Optimal Planting Timing
The most favorable time to plant asparagus crowns is in the early spring, as soon as the soil becomes workable after the winter thaw. This early timing allows the dormant crowns to establish roots before expending energy on spear and fern growth. The exact timing depends less on the calendar and more on the soil temperature, which should consistently reach about 50°F (10°C) for optimal crown activity.
Planting one-year-old crowns is the preferred method because it shaves a full year off the wait for a harvest compared to starting from seed. Seeds must be started indoors 12 to 14 weeks before the last expected frost and then transplanted after the danger of frost has passed. Crowns should be planted before their buds visibly break dormancy to minimize transplant shock.
Planting in cold, wet soil (below 45°F) is detrimental and increases the risk of crown rot. Waiting for the soil to warm slightly ensures the environment is conducive to root growth rather than fungal development. Spring planting is recommended across most regions for the best long-term success, though fall planting is possible in warmer climates.
Essential Site Preparation
Because asparagus is a long-lived perennial, the location must be chosen and prepared with permanence in mind. The site requires full sun exposure (at least eight hours daily) to ensure strong fern growth, which fuels the following year’s harvest. Excellent drainage is necessary, as the crowns will rot in waterlogged conditions, making raised beds a good choice if the native soil is heavy clay.
The soil must be deeply prepared to accommodate the massive root system, which can eventually extend 5 to 6 feet in diameter and up to 15 feet deep. Loosen the soil to a depth of 12 to 18 inches to improve aeration and promote deep root penetration. Asparagus prefers a soil pH that is slightly acidic to neutral, ideally ranging between 6.5 and 7.0.
The most time-intensive preparation is eradicating perennial weeds, which are almost impossible to manage once the patch is established. Weeds like bindweed or Johnsongrass must be controlled the season before planting, often requiring repeated deep cultivation or a “stale seedbed” technique. This involves irrigating the plot to germinate weed seeds and then lightly cultivating the surface to kill the seedlings. Prior to planting, incorporate liberal amounts of well-aged compost or well-rotted manure to enrich the soil. Only aged organic matter should be used, as fresh, actively decomposing material can damage the new crowns.
Step-by-Step Planting Process
Once the site is prepared, begin by digging a trench, typically 12 inches wide and 6 to 8 inches deep. Adjust the depth based on soil type: 6 inches is better for heavy clay, while 8 inches suits sandy soil. Before planting, soak the bare-root crowns in lukewarm water for a few hours to rehydrate them.
Create a small soil mound (approximately 2 inches high) along the bottom of the trench. Place the crown on top, carefully spreading the fleshy roots out and draping them over the mound. Crowns should be spaced 12 to 18 inches apart within the trench.
The crown is initially covered with only 2 to 3 inches of the reserved soil, ensuring the buds are just covered. This partial backfilling prevents young spears from expending too much energy pushing through a deep layer of soil. As new shoots grow throughout the first season, gradually fill the trench with the remaining soil until the area is level with the surrounding ground.
Establishing the Patch and First Harvest Expectations
Proper care during the first three seasons determines the patch’s long-term productivity. In the first year, the focus is entirely on root establishment, and no spears should be harvested. All spears must be allowed to grow into the tall, feathery foliage, which acts as the plant’s food factory, photosynthesizing and storing carbohydrates for the following year’s production.
The first-year patch requires consistent moisture, about one inch of water per week, especially during dry spells. Weed control is continuous, as the young plants cannot compete effectively with weeds for nutrients and water. In the second spring, a limited harvest is possible for a short period, typically only one to two weeks, provided the ferns were vigorous the previous year.
The third year marks the beginning of a full, sustainable harvest, which can last for six to eight weeks in the spring. Once the ferns have died back naturally and turned brown in the late fall, cut them down to a couple of inches above the ground to prepare the crowns for winter dormancy. This patient approach ensures the patch remains productive for many years.