How and When to Harvest Asparagus

It takes patience to get asparagus to the point of harvest, but the low-maintenance, long-lived perennial needs only minimal care in the meantime. Once established, the fresh stalks produce for years. The rewards are that much fresher when the spring crop is ready to harvest from our own gardens.

Asparagus’ green spears capture spring in their flavor. In cultivation for 2,000 years, they are among the earliest vegetables to emerge after winter. The nutritious stems are high in folate (which helps us process iron), amino acids, vitamins, and minerals. The stalks develop quickly and reach peak flavor and texture in cool temperatures, slowing when summer heat sets in.

The best asparagus is young and tender, with a crisp snap. The high harvest season is usually May to early June, depending on your climate, where you can pick as often as every two days. Keep up with the season’s asparagus harvest by keying in on when and how to best pick the rich stems for all of their culinary goodness.

Growing Asparagus

Asparagus officinalis can live for 15 years or more with deep roots and spreading fronds. The ferny foliage creates a tall presence at as much as four to eight feet, depending on the variety. Placed in the back of the border, northern end cap of a bed, or along a fenceline, it sits quietly until roots establish for spear production to begin. It helps to have a dedicated plot or raised bed for the long-lasting residents.

There are two ways to start asparagus: from crowns (one or two-year-old buds and roots) or seeds. Crowns grow horizontally and send up vertical shoots and downward roots. They’re ready to harvest two years after planting. Seeds take three years to grow before they’re ready for eating. But, the investment of time and patience is worth it; once established, the cold-hardy perennials produce for years in USDA zones 3-9.

Asparagus spears grow quickly in early spring as soil temperatures reach 40°F (4°C) and above. They begin to slow by early summer. For the warm season, they set fronds to continue growing and developing strong roots for future seasons.

The spring crops perform best in organically rich, sandy, well-draining soil, though they tolerate various types. Good drainage is essential, as is regular moisture, as the roots establish. Full sun, with six or more hours of sunlight daily, is optimal. In cold climates, protection from late-season frosts preserves the newly emerging spears.

Companion plants for asparagus support the perennials through deterring pests like asparagus beetles. Good partners include tomato, eggplant, basil, and dill.

When to Harvest, and When to Stop

Pluck the spears when they reach 6 to 8 inches tall, and 10 at maximum. Opt for young, slender stems and skip thick, woody ones, which are tough and sinewy.

From newly-planted crowns, the harvest timeline looks like this:

The harvest runs for approximately six to eight weeks in late spring, with climate variables like dry conditions and early warmth impacting the timing. Stop harvesting as temperatures rise and growth slows.

The spears become the leafy fronds the plant needs for future seasons, so reserving the remainder for warm-season growth is beneficial. The fronds complete natural growing cycles for the plant, including photosynthesis and storing sugars in the crown and roots. This food becomes the energy for the next round of spears post-winter.

Other indicators to stop harvesting include short stems that develop the ferny fronds and those that stay very thin.

How to Harvest Asparagus

To harvest asparagus, snap the stems by hand just below the soil surface (or as close to the surface as possible). Snapping by hand is quick and easy, and won’t damage nearby spears.

You can also use a knife to cut the stems below the surface, though it risks nicking nearby developing shoots. It extends the shelf life the lower you cut (in the white, underground portion of the stalk). Hand-snapping often taps into green tissue, making it freshest closest to harvest time.

Storage

Fresh asparagus is tender, crisp, bright, and delicious close to harvesting. The spears store for about a week in the refrigerator. To store the excess, freeze or can the shoots, or enjoy them as zesty pickles.

To freeze asparagus, wash the spears and cut off the woody ends. Blanch them whole or in pieces before freezing. To blanch, place them in boiling water for two minutes and up to four minutes for thick stems. Follow up with an ice bath for the same length of time.

To keep them accessible for use in small amounts (and to keep the pieces from freezing together), place them on a parchment-lined baking sheet after blanching and cooling. Freeze the sheet until the pieces are firm, then transfer them to an airtight container or baggie for long-term freezing.

Maintenance: Weed, Irrigate, Fertilize

Tending the site post-harvest keeps the crop strong and healthy. Weed regularly to reduce crowding and competition for nutrients, moisture, and sunlight. Heavy weed pressure depletes the roots and shoots of essential resources.

About one inch of water per week, whether from rainfall or irrigation, is usually enough to support the perennials during the growing season. Asparagus doesn’t often show signs of drought stress, but supplemental irrigation helps during dry spells or heat waves. If soils are sandy, more frequent irrigation may be necessary (and less for heavy or clay soils that hold water).

A fertilizer application in spring helps boost nutrition. Topdress with compost in late winter/early spring for the added benefits of soil nutrition, aeration, and moisture retention. In rich soils, you won’t need extra fertilizer. In leaner soils, use an organic balanced granular or one higher in phosphorus. Apply it alongside the plant (sidedress), scratching it in lightly to avoid damaging shallow surface roots.

In late fall or winter, before new shoots emerge in spring, cut back or mow the brown, dry fronds.

Extending the Harvest

Asparagus produces prolifically over its two months of maturing, especially in the few weeks of peak yield. There are ways to stagger the harvest for rewards of an early and late season round. One is to remove mulch from half of the bed to expose soils and roots to the sun’s warmth. This portion begins to grow more quickly than the mulched component. When shoots pop up through the mulched section, remove that layer. The first round will be ready first, overlapping with the later round.