Asparagus is a perennial vegetable that requires specific timing for two activities: the annual spring harvest of edible spears and the late-season maintenance of the foliage, known as ferns. Understanding the correct timing for both the harvest and the cleanup is important for maintaining a healthy, long-lasting asparagus patch. Proper management ensures the root system, or crown, has the energy reserves needed to produce a strong crop year after year.
Establishing the Patch: When to Begin Harvesting
The first two to three years after planting asparagus crowns require patience to establish a strong root system. In the first year, all emerging spears should be left uncut and allowed to grow into full ferns. These ferns photosynthesize all summer, transferring energy back down to the crown, which is essential for building a robust, productive plant. Removing spears too early severely weakens the young plant and reduces its yield potential for many years.
In the second year, most gardeners still recommend restraint. If the crowns appear particularly vigorous, you may take a very light harvest for only a short period, perhaps one to two spears per crown for one week at most. Stop harvesting quickly to allow the majority of spears to develop into ferns, continuing the crucial process of crown strengthening. The third year is generally considered the first time an asparagus patch is mature enough to withstand a full harvest season.
Harvesting the Mature Patch: Timing and Technique
The harvest season for a mature patch begins in early spring, typically once the soil temperature is consistently above 50°F and new spears begin to emerge rapidly. Spears should be picked when they are about 6 to 10 inches tall and before the tips begin to loosen or “fern out.” Once the tips open, the spear converts energy into foliage, and lignin forms, making the lower portion tough and woody.
During the peak of the season, you may need to check the patch and harvest spears every day, as warm temperatures can cause rapid growth. There are two common methods for removing the spears. One method is to use a sharp knife or specialized asparagus cutter to slice the spear an inch or two below the soil surface. This technique yields a longer spear, but requires care to avoid accidentally damaging the underground crown or nearby developing spears.
The second, simpler method is snapping the spear by hand. To do this, you bend the spear near the soil line, and it will naturally break off at its lowest tender point. This ensures you only harvest the edible portion, leaving the tough, fibrous base behind. The harvest season generally lasts six to eight weeks for a fully mature bed. Stop harvesting immediately when the diameter of the new spears consistently shrinks to the width of a pencil or smaller, indicating the crown is running low on stored energy and needs to recuperate.
End-of-Season Maintenance: Cutting Back the Ferns
After the spring harvest season ends, all remaining spears must be allowed to grow unhindered into tall, feathery ferns. This green foliage is responsible for generating and storing the carbohydrates that fuel the next year’s spear production. It is important not to cut these ferns back prematurely, even if they become messy or begin to yellow slightly in late summer.
Maintenance cutting occurs in late fall or early winter, specifically after the ferns have completely yellowed or browned following a hard frost. The color change signals that the foliage has finished transferring all its stored energy down to the crown. Cutting the ferns back to about two inches above the ground helps eliminate potential overwintering sites for pests, such as the asparagus beetle, and prevents the spread of disease spores. The cut ferns should be removed from the garden area and disposed of rather than composted.