Sweet Potato (Ipomoea batatas)
7 sources cited · Verified
The short answer
- Sow
- Early April to late April
- Plant out
- Mid May to mid June
- Ready in
- 100–150 days
- Site
- 6+ hours of sun, soil pH 5–7
- Biggest risk
- Sweetpotato black rot
In the UK, sweet potatoes are sown early April to late April, planted out mid May to mid June, and are ready to harvest 100–150 days after sowing.
Sweet potatoes (Ipomoea batatas) — perennial.
Timing is the decision that matters most in the UK: there are 4 separate regional planting out windows, ranging from mid May in Southern England to early June in Scotland.
Core growing advice on this page is checked against named horticultural and university-extension sources — see References.
Regional Planting Calendar
| Region | Sow | Plant out |
|---|---|---|
| Southern England | early April to late April | mid May to mid June |
| Midlands derived | mid April to mid May | late May to late June |
| Northern England derived | late April to late May | early June to late June |
| Scotland derived | early May to early June | early June to early July |
Rows marked derived are interpolated between regions our sources do state, because no source we consulted gives a figure for that region specifically. They are deliberately wider to reflect that uncertainty.
Southern England - detail & sources
Southern England: RHS gives no region-specific UK date, only "late spring or early summer, once the last frost has passed" -- this is the baseline reading of that rule for the mildest, earliest-clear UK region. Slips are potted up under cover from April and hardened off before planting out.
Midlands - detail & sources
Midlands: derived a week or so later than southern England, reflecting a later average last-frost date -- interpolated, since RHS gives one UK-wide rule rather than per-region dates.
Northern England - detail & sources
Northern England: derived later again for a later, more variable last frost -- interpolated from the RHS rule rather than a region-specific source.
Scotland - detail & sources
Scotland: derived to the latest and narrowest window in the UK -- a genuinely tender tropical crop this far north needs the surest possible frost clearance and the longest realistic run to a four-to-five month harvest before autumn frost, which for many Scottish gardens means growing under glass throughout rather than planting out at all. Interpolated from the RHS rule.
Quick Facts
| Factor | Value |
|---|---|
| Soil pH | 5 - 7 |
| Sunlight | 6-6 hours direct sun |
| Germination temp | 24C |
| Optimal growing temp | 18-28C |
| Minimum survivable temp | 1C |
| Time to harvest | 100-150 days |
| Drainage | Moisture-retentive, free-draining |
| Lifecycle | perennial |
| Edible parts | storage roots |
At a Glance
Soil & Growing Conditions
Soil pH range
Span reflects genuine variation between the cited authorities, not a single agreed figure.
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Slips & establishment | 0 | Grown from rooted cuttings ("slips") rather than seed tubers, available from online veg plant suppliers from late April. Pot up and grow on under cover until frost risk has passed. RHS. |
| Planting out | 3 | Plant out at least 30cm apart in late spring or early summer, once all frost risk has passed. The crop is tender throughout and must be protected from frost; it thrives at 21-26C, which is why it is best grown under cover in the UK -- a greenhouse, or cloches and fleece outdoors. RHS. |
| Vining growth | 6 | Trailing or climbing stems easily reach 1.5m or more in length as the plant bulks up through summer, well before any sign of the tubers developing below. RHS. |
| Harvest & curing | 8 | Most varieties need at least four to five months from planting; "Bonita" takes about 100 days. Harvest once the leaves yellow and die back in early autumn, before any frost -- tip the plant out of its container or lift with a fork. Dry tubers in warm sunshine for a few days to improve storage, though they generally keep for only a few weeks. RHS. |
Harvest & Storage
When to pick: RHS: "Bonita" takes "about 100 days from planting slips to harvesting"; most varieties require "at least four to five months"; harvest "once the leaves turn yellow and die back in early autumn, before any frost". UMD: days to maturity "85 to 120"; check root size "after 80 to 85 days because they don't stop growing"; roots "can start to split when overgrown"; harvest "before a frost".
Storage
Cure and store in cool, dry conditions for long-term keeping
Diseases
Pests
Sweet Potato, Slip to Harvest
References
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Tier 1. RHS factsheet on glasshouse red spider mite (two-spotted spider mite), naming tomato and strawberry among the host plants affected under glass or in a polytunnel.
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Directly fetched and verified. RHS explicitly distinguishes yellow sticky traps as a monitoring tool rather than a standalone control method, and notes traps also catch non-target parasitoid wasps -- a genuine trade-off between two control methods, preserved rather than simplified. No specific pesticide/insecticidal soap product is named on this page (RHS links out to a general pesticides statement instead), so none is recorded here.
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country=USA
7 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.
Frequently Asked Questions
When should I plant sweet potatoes out in the UK?
In Southern England, from mid May. In Scotland, wait until early June. Treat these as a guide rather than a fixed date — the governing rule is to plant out only once frost risk has passed and temperatures are reliably warm enough.
When do I sow sweet potatoes?
Sow early April to early June, at around 24°C for germination.
How long do sweet potatoes take to grow?
Typically 100–150 days, depending on cultivar and growing conditions.
What soil pH do sweet potatoes need?
A pH of about 5–7. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.
What problems affect sweet potatoes?
Our data links 2 diseases and 2 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
Most of the advice on this page comes down to timing and spacing — sowing at the right moment, rotating beds, and giving plants enough airflow. The UK Garden Planner lays your plot out month by month so those decisions are already made before the season starts.
Get the UK Garden Planner →Instant PDF download · Written for UK growing conditions
Where To Go From Here
Take this crop from reading into a written plan for your own beds.
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.