Asparagus Seeds: Care and Growing Guide
Growing asparagus from seed takes 3 years to first harvest but costs far less than crowns. US guide covers germination, transplanting, care by USDA zone.
Key takeaways
- Asparagus from seed takes 3 years before harvest; from crowns (1-year-old plants), it takes 2 years — seeds cost significantly less but require more patience
- Start seeds indoors 12–14 weeks before last frost or direct sow outdoors when soil reaches 50°F; germination takes 14–21 days at 70–85°F
- Asparagus needs deeply prepared, well-drained soil with organic matter worked in 12–18 inches deep — the crown and roots grow large over decades
- Plant in full sun in USDA zones 2–9; avoid zones 10+ where warm winters prevent the required cold dormancy period
- Male varieties like 'Jersey Knight' and 'Jersey Giant' produce 3 times more spears than female plants and don't produce seeds that become weeds
Why grow asparagus from seed?
Asparagus is one of the few truly permanent perennial vegetables, producing harvests for 20–30 years from a single planting. Growing from seed takes 3 years to first harvest but costs far less than buying crowns — a packet of 50 seeds costs $3–$5 versus $2–$4 per crown at the nursery.
For a 25-plant bed, the difference is $80–$100 in crowns versus $5 in seeds. You plant once and harvest for decades, so the economics of starting from seed improve dramatically over time.
The downside is patience — seed-started plants spend their first two seasons building root mass rather than producing harvestable spears.
Asparagus seed varieties
Not all asparagus varieties are equal. The most important trait for US home gardens is sex — male plants produce far more spears than female plants, and they don’t produce seeds that germinate as weeds throughout the bed.
| Variety | Type | Zones | Notes |
|---|---|---|---|
| Jersey Knight | All-male hybrid | 3–8 | Disease-resistant; top commercial choice |
| Jersey Giant | All-male hybrid | 3–9 | Large spears; good yield |
| Jersey Supreme | All-male hybrid | 3–8 | Early bearing; good for shorter seasons |
| Purple Passion | Male-dominant open pollinated | 4–8 | Purple spears; milder flavor |
| Mary Washington | Open pollinated (mixed sex) | 3–8 | Widely available; lower yield than hybrids |
| Apollo | Open pollinated | 4–10 | Warm-climate tolerance |
Why all-male hybrids win: Research from Rutgers University (where the Jersey series was developed) shows all-male plants produce 3–4 times more harvestable spears per plant than female plants over a 10-year period.
Growing asparagus from seed: step by step
Step 1: Start seeds indoors
Start seeds 12–14 weeks before your last frost date. In most of the US, this means February for March-May transplanting.
Germination requirements:
- Soil temperature: 70–85°F (a heat mat helps significantly)
- Moisture: consistently moist but not waterlogged
- Time: 14–21 days; soaking seeds 24–48 hours in warm water before sowing cuts this to 10–14 days
Sowing:
- Fill small cells or a seed tray with moist seed-starting mix
- Plant seeds 1/4 inch deep, one per cell
- Cover with plastic wrap or a humidity dome until germination
- Remove cover when sprouts appear and move to bright light
Asparagus seedlings look like very thin grass for the first month. The ferny fronds develop gradually.
Step 2: Transplant to larger containers
When seedlings reach 8–10 inches tall (about 6–8 weeks after germination), transplant into 3-inch or 4-inch pots with potting mix. Continue growing indoors or in a cold frame.
Do not rush outdoor transplanting — asparagus roots benefit from a full indoor season of development.
Step 3: Prepare the asparagus bed
Asparagus stays in place for decades. Prepare the bed as thoroughly as any permanent installation in your yard.
Site requirements:
- Full sun (6+ hours)
- Well-drained soil — wet clay causes crown rot that kills established plants
- Away from trees and large shrubs that compete for water and nutrients
- A permanent location not needed for crop rotation
Soil preparation:
- Mark the bed: asparagus rows are typically 3–4 feet apart, with 18 inches between plants
- Dig a trench 12–18 inches deep
- Mix in 2–3 inches of compost and 1 cup of balanced granular fertilizer per 10 feet of row
- If your soil drains poorly, raise the bed 6–8 inches to improve drainage
See how to start a vegetable garden for guidance on site selection and bed construction.
Step 4: Transplant seedlings outdoors
Transplant after your last frost date when seedlings are 10–12 weeks old.
- Dig individual holes 6–8 inches deep in prepared soil
- Mound a small cone of soil in the center of each hole
- Set the seedling root mass over the mound and spread roots down the sides
- Cover with 2 inches of soil
- Water thoroughly
Spacing: 18 inches between plants in the row, 3–4 feet between rows.
Growing asparagus from crowns vs. seeds
| Factor | Seeds | Crowns |
|---|---|---|
| Cost | $3–$5 per packet (50+ seeds) | $2–$4 per plant |
| Years to harvest | 3 | 2 |
| Disease risk | Lower | Higher (crowns can carry diseases) |
| Availability | Year-round online | Spring only |
| Labor | High (indoor starting, two transplants) | Moderate (one outdoor transplant) |
If you’re starting a large asparagus bed (50+ plants), seeds are the practical choice economically. For a small bed or first-time growers, crowns save a year of waiting with modest extra cost.
If you choose crowns, plant them in early spring when the soil reaches 50°F and frost risk is past. In zones 5–6, that’s typically April; zones 7–9, March.
First-year and second-year care
Year one (seed year)
The first summer after transplanting, allow all fronds to grow without harvesting. The plant needs to photosynthesize aggressively to build root mass.
- Water deeply every week during dry periods (1 inch of water)
- Keep the bed weeded — young asparagus competes poorly with weeds
- Mulch with 2–3 inches of straw or wood chips to retain moisture and suppress weeds
- In fall, after fronds yellow, cut them down to 2 inches above the ground
Year two
In year two, you may be tempted to harvest. Resist for crown-grown plants in year two, and definitely resist for seed-started plants in year two. Allow all growth again.
Weed control remains critical. Asparagus roots can extend 6 feet wide — they pull nutrients from a large area, and weeds compete for that space.
The raised bed garden plans guide discusses how permanent crops like asparagus fit into raised-bed layouts.
Year three and beyond
Year three is your first real harvest. Limit it to 2 weeks maximum in year three to continue building root strength. In year four and beyond, harvest for 4–8 weeks.
When to harvest:
- Cut spears when they reach 7–9 inches tall and the tip scales are still tightly closed
- Cut 1–2 inches below the soil surface with a sharp knife or snap the spear at ground level
- Harvest daily during peak season — spears grow 2–3 inches per day in warm weather
Stop harvesting when: spears start emerging thinner than a pencil. This signals the plant needs energy to rebuild roots for next year. Let them grow into fronds after this point.
Watering and fertilizing established asparagus
Watering: Established asparagus is moderately drought tolerant. Water 1 inch per week during dry periods and more during the active harvest season.
Drip irrigation works well for asparagus — consistent moisture at the root zone without wetting foliage reduces fungal disease risk. See drip irrigation system for setup options.
Fertilizing:
- Apply balanced fertilizer (10-10-10) in early spring before spears emerge — 1.5 lbs per 100 square feet
- Apply a second time immediately after harvest season ends in June or July
- Avoid high-nitrogen fertilizers, which push leafy growth at the expense of root energy storage
Common problems
Crown rot (Fusarium)
The most serious asparagus disease in the US. Infected crowns turn brown and mushy; spears emerge thin and spindly, then stop emerging. Fusarium lives in soil.
Prevention: plant all-male hybrid varieties, which have resistance; avoid wet soils; rotate starting locations if crowns are disease-prone (though asparagus is typically permanent — start with healthy crowns).
Asparagus beetles
Two asparagus beetle species attack US gardens: common asparagus beetle (Crioceris asparagi) and spotted asparagus beetle. Adults and larvae feed on spears and fronds, causing scarring.
Control: hand-pick adults and eggs; allow fronds to grow after harvest to support natural predators. Spray with insecticidal soap or pyrethrin if infestation is heavy.
Purple spot
A fungal disease that causes purple lesions on spears. Favors wet conditions. Improve air circulation and avoid overhead irrigation.
Asparagus rust
Orange-rust pustules appear on fronds. Reduces vigor if severe. Planting resistant varieties (all Jersey series) prevents most infection.
Asparagus in the US kitchen garden
Asparagus is one of the highest-value crops in terms of flavor-per-square-foot for US kitchen gardeners. Fresh asparagus lasts 3–5 days in the refrigerator (stand the spears upright in a glass with a half-inch of water, then cover with a plastic bag). For freezing, blanch spears for 2–3 minutes, cool immediately in ice water, and freeze flat on a tray before bagging.
For companion planting alongside asparagus, tomatoes and parsley are traditional companions — both are claimed to deter common pests, though companion planting chart data shows the tomato-asparagus relationship is more anecdotal than tested.
According to the USDA National Agricultural Statistics Service, US asparagus production has shifted from the Midwest to California over the past 20 years as growers sought longer growing seasons, but home garden asparagus continues to thrive in zones 3–8 where commercial production is impractical.
Sarah Mitchell is a Master Gardener and garden writer based in the Pacific Northwest. She has been growing food and flowers for over 15 years across USDA zones 7 and 8.