When to plant asparagus in RHS H2 (UK)

Key dates for asparagus at RHS H2

Dates are typical for the regions H2 describes (Isles of Scilly, Channel Islands, the warmest sheltered pockets of west Cornwall and south Devon). UK frost pockets, urban heat, and coastal moderation can shift the planting window by 1-2 weeks within the same rating band. Always cross-check against your local Met Office station for current conditions.

Why this timing works at H2

H2 describes UK gardens with winter minima of minimum 1-5 °C. Last spring frost typically passes mid-March (Scilly Isles, Channel Islands); first autumn frost arrives late November, giving about 250 frost-free days.

Asparagus is almost always established from year-old crowns rather than seed; plant them in a prepared trench 20-30 cm deep as soon as the soil can be worked in early spring, 2-3 weeks before the last frost. Do not harvest at all in year one, harvest sparingly for 2-3 weeks in year two, and from year three onward you can take a full 6-8 week spring harvest. Crowns are reliably cold-hardy to zone 3 but require winter dormancy — they are poorly suited to zones 10-11 where winters are too warm to meet the chilling requirement.

UK-specific tips for H2

• Asparagus grow well outdoors in the Scilly Isles and Channel Islands but are still vulnerable to occasional spring frosts — keep horticultural fleece to hand through April.
• Slug pressure is severe in mild damp winters — start beer traps and copper rings in March, not when you see damage.
• Wind exposure trumps temperature in H2 coastal pockets. Salt-laden gales burn foliage as quickly as any frost — establish a windbreak before you plant.

Quick-grow guide

• Sun: Full sun — 6-8 hours direct.
• Soil temperature for germination: Soil 10-18 °C (50-65 °F) at crown planting.
• Spacing: 12-18 inches (30-45 cm).
• Days to harvest from direct sow: ~730 days.
• Wait until soil reaches 10-12 °C before transplanting outdoors — cold UK soils stall tender crops for weeks.

Common mistakes — H2 × asparagus

• Treating UK climate like the US zone 10: although temperature minima match, UK summers are cooler, wetter, and cloudier. Add 1-2 weeks to days-to-harvest figures from US sources.
• Sowing into cold wet soil: UK spring soil holds water longer than equivalent US zones. Wait for soil to dry enough to crumble in your hand before sowing.

Source and methodology

RHS hardiness rating thresholds from the official RHS reference. Typical frost-date averages from Met Office regional climate summaries for the geographies H2describes. Crop timing offsets calibrated against UK extension references (RHS sowing calendar, Garden Organic, James Wong's UK growing tables) and cross-checked against US Cooperative Extension Service publications. For American readers cross-referencing, RHS H2 is roughly equivalent to USDA zone 10. Curated by the Growli editorial team.

Keep going

• How to grow asparagus — full guide
• RHS H2 — typical regions and what else to plant
• All RHS hardiness ratings (H1a-H7)
• USDA hardiness zones — for cross-reference with US sources
• Fungus gnats in UK houseplants — guide

Same crop, nearby ratings

• When to plant asparagus in RHS H3
• When to plant asparagus in RHS H4

Other crops at H2

• When to plant tomatoes in H2
• When to plant peppers in H2
• When to plant basil in H2
• When to plant garlic in H2
• When to plant lettuce in H2
• When to plant bush beans in H2