RHS H5 UK planting calendar
When to plant garlic in RHS H5 (UK)
Sowing, planting, and harvest dates calibrated to H5's 150-day UK season (The Midlands, northern England, inland Wales, lowland Scotland — the band most UK gardens actually sit in once you leave the south coast).
Key dates for garlic at RHS H5
| Stage | When | Anchor |
|---|---|---|
| Plant cloves outdoors | early September — mid-September (about 35 days before the first autumn frost) | 35 days before first autumn frost (mid-October) |
| First harvest (estimate) | early May of the following year | ~240 days from autumn planting |
Dates are typical for the regions H5 describes (The Midlands, northern England, inland Wales, lowland Scotland — the band most UK gardens actually sit in once you leave the south coast). 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 H5
H5 describes UK gardens with winter minima of minimum -15 to -10 °C. Last spring frost typically passes mid-May; first autumn frost arrives mid-October, giving about 150 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. H5 delivers reliable chill — both hardneck and softneck work.
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 H5
- H5 covers most of the inhabited UK — Midlands, northern England, lowland Scotland — and garlic need the timing to be more conservative than southern England.
- Cloches and a low polytunnel extend the season at both ends — worth 3-4 weeks of usable growing time in spring and another 2-3 weeks in autumn.
- Cold wet springs are the main pest stress — slugs build up populations in damp soil, and seedlings stall in cool weather. Sow into trays and transplant when soil is reliably above 10 °C, rather than direct-sowing into cold beds.
- Mulch all overwintering plants in November — even hardy perennials lose ground in a freeze-thaw cycle without a 5-7 cm cover of straw or composted bark.
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 — H5 × garlic
- Treating UK climate like the US zone 7: 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 H5describes. 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 H5 is roughly equivalent to USDA zone 7. Curated by the Growli editorial team.
Keep going
- How to grow garlic — full guide
- RHS H5 — 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
- When to plant garlic in RHS H6
- When to plant garlic in RHS H7