When to plant garlic in RHS H2 (UK)

Key dates for garlic 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. Garlic need a cold period to bulb properly. Plant cloves in autumn so roots establish before the ground freezes; they overwinter dormant and break growth in spring. H2 delivers limited chill — softneck varieties are the right pick.

Garlic is the unusual one — plant cloves in autumn (4-6 weeks before the first hard fall frost) so they put down roots before winter, then break dormancy in spring and bulb up over the long days of early summer. Cold-winter zones grow hardneck varieties; mild-winter zones do better with softneck.

UK-specific tips for H2

• Garlic 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+ hours direct.
• Soil temperature for germination: Soil 10-15 °C (50-60 °F) at planting.
• Spacing: 4-6 inches (10-15 cm).
• Days to harvest from autumn planting: ~240 days.
• Mulch with 5-7 cm of straw or shredded leaves once temperatures drop in November.

Common mistakes — H2 × garlic

• Choosing hardneck varieties: H2 winters don't deliver enough chill hours for hardneck garlic — softneck (Solent Wight, Picardy Wight) is the right pick for mild coastal UK.
• Planting too early in autumn — warm soil in October triggers green growth before winter, weakening the bulb.

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 garlic — 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 garlic in RHS H3
• When to plant garlic 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 lettuce in H2
• When to plant bush beans in H2
• When to plant cucumbers in H2