How to Grow Asparagus

Crowns, the trench, and gradual backfilling

Almost everyone starts asparagus from one-year-old crowns bought from a garden center or catalog rather than seed, because crowns skip a year of growing and get you to harvest faster. (You can start seed indoors in January for April transplanting if you prefer.) Choose the site carefully, because this bed will stay put for well over a decade.

Dig furrows about 8 inches deep (shallower in heavy clay, deeper in very sandy soil), set the crowns 12 inches apart in the row with rows about 4 feet apart, spreading the roots out. Then cover the crowns with only about 2 inches of soil to start rather than filling the trench all at once.

As the spears grow into ferns, slowly backfill the furrow over the season, adding a couple of inches of soil every so often until it is level by season's end. This gradual filling lets the shoots keep reaching light while the crown ends up planted at good depth.

The two-year wait — and why it pays

The hardest part of growing asparagus is not cutting it. Utah State Extension is blunt: do not harvest until year three after planting. Those first two seasons, the plant is building a large root storage system, and every spear you leave standing feeds that system.

Harvesting too much too early leads to weak plants and lower yields for years afterward. So in years one and two you let all the spears grow up into tall, ferny foliage and simply admire the patch. It feels wasteful and it is the whole game.

After the ferns yellow and die back in fall, mow or cut them down and clear the debris. That standing fern all summer is what powers next spring's spears, so never remove green ferns during the growing season.

Harvesting, year by year

Once you reach year three, ramp up the harvest gradually. Utah State suggests a light harvest of about 4 weeks in year three, roughly 6 weeks in year four, and up to 8 weeks from year five onward, after which the plants tell you to stop as spears thin down.

Cut spears at ground level when they are about 9 inches tall and still tight-tipped, and harvest all of them during the picking window, since tall spears left to fern over suppress further spear production. When spears coming up get pencil-thin, stop cutting and let the bed fern out for the season.

The reward for all this patience is longevity: expect the planting to produce spears for 10 to 15 years, and often longer. For crown-planting depth and spacing specifics and the first-harvest rule, see the asparagus crown-planting and first-harvest pages.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• Utah State University Extension — How to Grow Asparagus in Your Garden — Plant 1-year-old crowns (or start seed in January for April transplanting) in 8-inch-deep furrows, spacing plants 12 inches apart in rows 4 feet apart, covering crowns with 2 inches of soil and slowly backfilling 2 inches every other month until furrows are filled; do not harvest until year 3 after planting; harvest window is about 4 weeks in year 3, 6 weeks in year 4, and up to 8 weeks in year 5+; cut 9-inch-tall spears at ground level and harvest all spears since tall spears suppress further growth; the planting produces spears for 10-15 years; allow spears to develop into fern after harvest and mow down after ferns die in fall.
• Illinois Extension — How to successfully grow asparagus in your garden (Good Growing) — Dig a 6-12 inch deep furrow for crowns (6-8 inches in heavy clay, 10-12 inches in very sandy soil), cover crowns with 2-3 inches of soil and add the remaining soil a few weeks later once ferns emerge; patience is required because harvesting too much too early leads to weak plants and lower yields; do not harvest the year of planting, harvest lightly the following years, with fuller harvest windows building over subsequent seasons.

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