Asparagus grows back every year because it is a perennial plant, meaning it lives for more than two growing seasons. This vegetable, known scientifically as Asparagus officinalis, can produce tender spears for 15 to 30 years with proper care. Its yearly return is sustained by a robust, underground structure that stores the energy needed to survive the winter and fuel the spring harvest. The plant’s longevity and consistent production cycle make it a rewarding addition to any garden space.
The Biology of Asparagus Crowns
The mechanism that allows asparagus to return each year is a subterranean root structure called the crown, which functions as the plant’s permanent storage unit. This crown is a fleshy rhizome that develops a dense, fibrous root system extending deep into the soil. The roots can grow extensively, reaching up to 10 to 15 feet deep and wide, providing anchorage and absorbing nutrients and water.
The annual cycle begins in spring when the soil temperature rises above 50°F, prompting the crown to push up edible shoots, known as spears. If these spears are not harvested, they quickly develop into tall, fern-like foliage that can reach heights of three to five feet. This foliage acts as the plant’s food factory, converting sunlight into energy through photosynthesis throughout the summer.
This energy is then transported back down to the crown and roots for carbohydrate storage. As fall approaches, the ferns naturally yellow and die back, signaling the plant has entered its dormant phase for the winter. The stored energy in the crown sustains the plant through the cold months and provides the fuel for the following spring’s emergence of new spears.
Establishing a Permanent Asparagus Bed
Because asparagus can remain productive for decades, establishing the bed correctly from the start is important to its success. The planting site must be chosen carefully, requiring full sun—at least six to eight hours of direct sunlight daily—to maximize the fern’s ability to produce energy. The soil must be loose, deep, and well-drained, as the crowns are susceptible to rot if left in standing water.
Asparagus is typically planted using one-year-old dormant root bundles, called crowns, rather than seeds, which take an extra year to establish. The crowns are planted in a trench, usually six to eight inches deep, with the roots spread out over a small mound of soil. As the spears grow throughout the first season, the trench is gradually filled with soil, which encourages the crown to set deeper in the ground.
Patience is necessary, as the first two to three years after planting are dedicated to root establishment rather than harvesting. All spears in the first year must be allowed to grow into ferns to build up the crown’s initial carbohydrate reserves. Harvesting too early or too aggressively will weaken the young plants and shorten the productive lifespan of the entire bed.
Annual Harvesting and Seasonal Care
Once the asparagus bed is fully established, typically by the third or fourth year, a reliable harvest can begin each spring when the spears emerge. The harvesting window generally lasts for six to eight weeks, ending around late June or early July. Spears are ready to be picked when they are six to ten inches tall and at least a half-inch thick.
The proper technique is to snap the spear off by hand near the soil line or cut it with a knife just below the surface. It is important to stop harvesting when the diameter of the new spears begins to shrink. Any spears that are not harvested must be allowed to fully develop into the ferny growth, which is responsible for manufacturing and storing the food reserves in the crown.
In the fall, once the ferns have naturally turned completely yellow or brown after a hard frost, they should be cut down to about two-inch stubs. This practice removes potential hiding spots for overwintering pests and prepares the bed for the next season. Applying a layer of compost or mulch helps to control weeds and insulate the crowns, ensuring they are ready to emerge again the following spring.