Asparagus is a perennial vegetable that can provide a fresh harvest for up to 20 years or more from a single planting. Planting asparagus correctly ensures the deep, robust root system necessary for decades of reliable production. The process involves careful site selection, soil amendment, and a specific planting technique known as the trench method. These steps are designed to support the plant’s long-term health and vigor.
Selecting the Site and Preparing the Plants
Asparagus requires full sun, needing at least six to eight hours of direct sunlight daily for optimal growth. Since the plants remain in place for many years, choose a site carefully, avoiding future disturbances or shade. The deep root system demands loose, well-drained soil, as roots are highly susceptible to rot.
Preparing the soil must begin well before planting, as amendments are difficult to incorporate once the crowns are set. The soil should be loosened to a depth of 12 to 15 inches. Asparagus prefers a neutral to slightly acidic soil (pH 6.5 to 7.0), so a soil test should determine if adjustments are needed. Work a generous amount of organic matter, such as aged manure or compost, into the planting area to improve fertility and structure.
Most gardeners plant one-year-old crowns, which establish faster than starting from seed. Selecting disease-resistant, all-male hybrid varieties, such as ‘Jersey Knight,’ is recommended because they channel energy into spear production rather than seed development, leading to higher yields.
The Trench Method: Step-by-Step Planting
The trench method is the traditional way to establish an asparagus bed, ensuring crowns are planted at the proper depth. Begin by digging a trench 12 to 18 inches wide and 6 to 12 inches deep. Deeper trenches (10 to 12 inches) are better for sandy soils, while shallower depths (6 to 8 inches) are preferable in heavy clay soils.
Form a ridge or small mound of soil and compost, roughly two inches high, down the center of the trench floor. Place the one-year-old crowns on top of this mound, carefully draping the roots down and spreading them out evenly on both sides. Crowns should be spaced 12 to 18 inches apart along the ridge to allow sufficient room for root development.
Cover the crowns with only two to three inches of excavated soil, just enough to bury the roots and crown buds. Follow this initial partial backfilling with a thorough watering to settle the soil and eliminate air pockets. As the first spears emerge and grow two to three inches tall, add another two inches of soil, being careful not to completely bury the shoots. This gradual backfilling continues over the first growing season until the trench is entirely filled to ground level.
Managing the First Year for Future Harvests
The first year of growth is dedicated entirely to root establishment and energy storage. Consistent weed control is crucial, as young asparagus plants compete poorly against aggressive weeds. Weeds should be removed by hand or with very shallow cultivation (less than two inches deep) to avoid damaging the developing roots.
Consistent moisture is necessary for the developing crowns, especially during dry spells. Asparagus should receive about one to two inches of water per week to encourage extensive root growth. The spears that emerge will quickly develop into tall, feathery ferns, which are responsible for creating and storing carbohydrates in the crowns. Allowing the ferns to grow unhindered throughout the summer directly determines the vigor and yield of the following year’s harvest.
The most important rule in the first year is to refrain from harvesting any spears. Harvesting too early depletes the plant’s energy reserves, resulting in weak spears and a shortened lifespan for the patch. In late fall, once the ferns have naturally yellowed and died back, cut them down to about two inches above the soil surface. A layer of mulch applied over the rows in the late fall helps to insulate the crowns and suppress early spring weeds.