How to Grow Asparagus: Planting, Spacing, Care & Harvest

Quick answer

Plant one-year crowns 4 to 6 weeks before last spring frost (Purdue). UMD uses a 6- or 12-inch trench with crowns 15 to 18 inches apart and rows 4 to 5 feet apart; UMN uses a 6- to 12-inch furrow by soil type with buds about 12 inches apart and rows at least 3 feet apart. Do not harvest the first season after planting crowns.

Green asparagus spears (Asparagus officinalis)
Evan-Amos, CC BY-SA 3.0, via Wikimedia Commons · source · license

Asparagus at a glance

PlantPlant crowns: 6–4 wk before last frost
SunUMD “Full sun requires direct light at least 6 hours/day; prefers 8 - 10 hours/day.”
WaterUMN at least one inch of water per week (more often on sand); important at planting and for fern growth after harvest.
SpacingUMD traditional trench: “12-inches deep and 12- to 18-inches wide, with 4 to 5 feet between trenches.”
Days to harvestPerennial; begin harvesting lightly in years 2 and 3 (UMD)
-7-6-5-4-3-2-1LF+1+2+3
■ Start indoors   ■ Plant out   ■ Harvest
Weeks relative to last frost (LF). Colored weeks show when our ZIP planner schedules each step.
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Planting dates for your ZIP: the ZIP planting planner counts each window from your local frost dates.

Organic pests and diseases: see also organic pest control. Use any product as the label directs.

Bundle of green asparagus spears
Asparagus spears. Photo: Evan-Amos, Wikimedia Commons, CC BY-SA 3.0 (resized).

Planting timing

Purdue HO-186: hardy crop — “plant 4-6 weeks before last spring frost.” (Purdue Extension) UMD: plant one-year crowns in early spring; “Crowns are usually shipped and set out in March or April” (Maryland calendar example). UMD when-to-plant table: Mid-March through mid-April for seedlings or bare-root crowns. (UMD Extension; UMD when to plant) UMN: “In Minnesota, asparagus is planted between early May and early June” (Minnesota calendar example — regional, not a national frost offset). (UMN Extension) Seed option: UMD starting from seed “requires an extra year before harvest”; seeds are “slow to germinate” and transplants go out in June (MD). UMN: nursery-bed seed in spring about one inch deep; move crowns to the permanent bed the next early April before growth starts. Hardiness: UMD “Hardy perennial can withstand winters with protection in colder areas; should be mulched in autumn.” NC State USDA zones 2a–9b. (NC State) Late spring frosts can kill emerged spears and cause bend/curl; site the bed out of frost pockets (UMN).

Depth and spacing

UMD traditional trench: “12-inches deep and 12- to 18-inches wide, with 4 to 5 feet between trenches.” Many gardeners succeed with a “6-inch trench.” Crowns “15 to 18 inches apart”; raise the crown slightly above the roots; spread roots over a 2-inch soil mound; cover the crown completely. Wide beds: “three rows with plants 18 inches apart in all directions.” Facts line: “18" in-row x 4' to 5' between rows.”

UMN: furrow 6–12 inches deep (shallower 6–8 in clay; deeper 10–12 in sand). Place crowns head-to-toe so buds are about 12 inches apart; multiple rows at least 3 feet apart. Cover with 2–3 inches of soil at planting; backfill as ferns grow. UMN: spreading roots “like an octopus” is outdated/unnecessary.

The sources differ on in-row spacing (UMD 15–18 in vs UMN ~12 in), between-row spacing (UMD 4–5 ft vs UMN ≥3 ft), and trench depth, so we show each with its source. NC State mature size: height 3–5 ft; width 1.5–3 ft.

Sun, soil and water

Sun: UMD “Full sun requires direct light at least 6 hours/day; prefers 8 - 10 hours/day.” NC State full sun (≥6 hours). UMN sunny, well-drained; put the bed at the north end of the garden so ferns do not shade other crops. Soil: UMD good drainage; enrich with compost. UMN well-drained, moisture-retentive; pH 6.5 to 7.0; does not tolerate extremely acidic soils. NC State moist organic sandy soil, good drainage, neutral pH 6.0–8.0; salt-resistant for coastal sites. Water: UMN at least one inch of water per week (more often on sand); important at planting and for fern growth after harvest. UMD keep the bed well watered after planting. Mulch / weeds: UMD weed before first shoots; pull weeds during production (hoe risks broken spears); after frost cut foliage to 2-inch stubs and apply 4- to 6-inch mulch. UMN hand-weed; shallow cultivate only before spears emerge and after harvest ends (<2 inches deep); mulch can delay spring emergence — push aside in early spring to warm soil.

Care

Longevity: UMD lives 12 to 15 years or longer. UMN “An asparagus plant can last 15 years.” Fertilizer: UMD medium-high nutrient need; add organic matter before planting; nitrogen each early spring; side-dress after harvest; yearly compost top-dress. Soil test (UMN). Do not use fertilizer that contains a weed killer (UMN). Winter: UMD cut yellowed ferns to 2-inch stubs after frost and before red berries fall (all-male plantings produce no berries). UMN remove dormant brown ferns to cut beetle overwintering; wait until ferns are fully dormant.

Harvest and storage

UMD: “Begin harvesting lightly in years 2 and 3.” No harvest the first season after crowns; lightly 3 to 4 weeks the second year; from seed, no harvest the first two seasons, light third; fourth season 8 to 10 weeks per year. UMN: no harvest the first spring after crowns; second spring harvest only two weeks if plants were strong; later years harvest until about July 1 (MN). Peak season spears can grow up to 2 inches per day (UMN). Method: UMD snap 6- to 8-inch spears just below the soil surface; cutting too deep injures crown buds. UMN harvest when spears are six to eight inches long. Yield (UMD): about 3 to 4 pounds per 10-foot row per year. Storage: UMD process or refrigerate immediately in a mesh or plastic bag. UMN keep up to a week in the refrigerator (plastic bag, crisper); can freeze; pressure-can only for canning. NC State: berries may cause gastrointestinal problems; contact dermatitis possible from young raw shoots (wear gloves). Do not eat berries.

Pests and diseases (organic)

Asparagus beetles (common and spotted): UMD lists common asparagus beetle (Crioceris asparagi) and spotted (Crioceris duodecimpunctata); larvae grayish green with black heads; eggs shiny black, attached by one end to spears; two generations per year in Maryland. Cultural: “Harvest spears as early as possible”; leave a small unharvested area as a trap crop; “Thoroughly remove all plant debris” after harvest. Biological: parasitic wasp Tetrastichus asparagi; lady beetles. (UMD asparagus beetles) UMN: beetles scar spears and can cause shepherd’s-crook bend; aphids and cutworms also listed. Remove dormant ferns to reduce overwintering; harvest thoroughly.

Aphids: strong water spray; insecticidal soap or oil with thorough coverage; not on water-stressed plants or above 90°F; follow the label (UC IPM aphids).

Cutworms: UMN: cutworms cut spears at the base; frost and herbicide drift can also bend spears.

Rust (Puccinia asparagi): UMN: yellow and rusty orange spots on stems after harvest. Cultural: regular harvest of all spears reduces rust risk; remove infected ferns before spring. UC IPM: cut and destroy diseased ferns at end of season; cut young spears in spring to break the cycle; sulfur dust is organically acceptable but weak — follow the label (UC IPM rust).

Fusarium / crown rot: UMN: poor growth, yellow dieback, brown decayed crowns when cut open; start with healthy crowns; avoid wet poorly drained sites; avoid replanting asparagus where it grew within five years; do not overharvest. UC IPM also lists Phytophthora crown and spear rot — good drainage, do not overwater (UC IPM asparagus).

Related: ZIP planner · organic pest control

Frequently asked questions

When do I plant asparagus crowns?

Purdue: 4–6 weeks before last spring frost. Pair with local soil workability (UMD/UMN calendar examples).

How deep and how far apart?

Present UMD (6- or 12-inch trench; 15–18 in in-row; 4–5 ft rows) and UMN (6–12 in by soil; ~12 in bud spacing; ≥3 ft rows) with sources — do not invent a single number.

When can I harvest?

No harvest the first season after crowns (UMD; UMN). Light harvest year 2; full-season harvest only after the bed is established (UMD 8–10 weeks by year 4; UMN through about July 1 in later years).

How do I reduce asparagus beetles without a spray?

Early daily harvest, a small fern trap patch, and thorough removal of fern debris after the season (UMD).

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Sources