How to Grow Sweet Potato
Ipomoea batatas
Sweet potatoes need heat, full sun, and a long, frost-free season. Plant slips (rooted cuttings) after nights are warm, into loose, fertile, free-draining soil—raised ridges or black plastic warm the root zone. Space generously and keep even moisture through tuber bulking; avoid high nitrogen. Train vines to keep beds tidy. Lift before frost when leaves yellow; handle gently to avoid bruising. Cure harvested tubers warm and humid for 1–2 weeks to sweeten, then store cool (not cold) and dry.
When to Start
Best started from plugs, corms, or slips. Pot up indoors 5 weeks before last frost, then plant out once soil reaches 18°C.
Don't know your frost date? Find it here →
Growth Stages
Approximate days from start
Care Essentials
- High-potash feed once tubers start forming. Avoid high nitrogen which promotes leaves over tubers.
- Needs a long, warm growing season. In the UK, grow under black plastic mulch or in a polytunnel for best results.
Companion Planting
Broad Beans, Runner Beans, Sweetcorn
Growing Conditions
- Min. soil temperature
- 18°C+
- Germination temperature
- 21–30°C
Pet Safety
- Direct sow
- —
- First harvest
- —
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Spacing & Planting
| Plant spacing | 30 cm |
| Row spacing | 75 cm |
| Sow depth | 5 cm |
| Mature height | 40 cm |
| Mature spread | 150 cm |
Plant rooted slips into warm soil (often under cover in the UK). Needs a long, warm season.
Companion Planting
Grows well with
Broad beans form symbiotic partnerships with Rhizobium bacteria that fix atmospheric nitrogen into plant-available ammonium, which leaches into the surrounding soil and feeds the nitrogen-hungry sweet potato vines. Sow beans 3–4 weeks ahead so nodules are active before sweet potato transplants go in.
▼Runner beans fix atmospheric nitrogen via root nodule bacteria, releasing ammonium into the soil that sweet potato vines absorb through their shallow, spreading root system. Train runner beans on a trellis at the north end of the bed so they don't shade out the light-demanding sweet potato foliage.
▼Tall sweetcorn stalks cast afternoon shade that moderates soil temperature and reduces moisture stress for sweet potato vines sprawling at ground level. Plant corn on the west side of the bed so morning sun still reaches the sweet potato leaves during their peak photosynthesis hours.
▼Dill's flat umbel flowers are landing platforms for parasitic wasps and hoverflies whose larvae prey on whiteflies and caterpillars that attack sweet potato foliage. Allow dill to flower rather than harvesting all the fronds, positioning plants at bed edges so their tall stems don't shade the vines.
▼Thyme's aromatic thymol and carvacrol volatiles act as olfactory camouflage, disrupting the host-finding behaviour of sweet potato weevils and whiteflies. Plant thyme as a low border around sweet potato beds — it tolerates drought similarly to sweet potato and won't compete for water.
▼Keep away from
Both sweet potato and tomato are susceptible to overlapping solanaceous diseases including Fusarium wilt and several viral pathogens that persist in soil, so growing them together increases disease pressure on both crops. Keep them at least 1.5 m apart and avoid following one with the other in rotation for at least 3 years.
▼Both sweet potato and pumpkin are vigorous ground-covering vines that rapidly spread horizontal stems, leading to intense competition for root space, soil moisture, and light at ground level. Separate them by at least 2 m or confine one to a raised bed to prevent the larger pumpkin from smothering the sweet potato.
▼Pests & Diseases
Pest Slugs and Snails
Identification: Holes and tunnels bored into tubers; slime trails on tuber surfaces; damage often only discovered at harvest
- Apply organic slug pellets (ferric phosphate based) around plants throughout the growing season
- Use nematode biological control (Phasmarhabditis hermaphrodita) applied to soil in warm weather
- Harvest promptly once foliage dies back to minimise underground slug damage
- Apply ferric phosphate slug pellets around plants
Pest Whitefly
Identification: Tiny white flying insects that rise in clouds when foliage is disturbed; sticky honeydew on leaves; sooty mould
- Introduce the parasitic wasp Encarsia formosa under cover
- Hang yellow sticky traps near plants
- Spray with insecticidal soap
- Spray with a contact insecticide containing pyrethrins
Pest Aphids
Identification: Clusters of green or black insects on leaf undersides and shoot tips; sticky honeydew; curled or distorted leaves
- Blast off with a jet of water
- Spray with insecticidal soap
- Encourage ladybirds and lacewings
- Spray with a contact insecticide containing pyrethrins
Disease Black Rot Ceratocystis fimbriata
Symptoms: Dark, sunken, circular lesions on tubers; bitter taste; dark discolouration inside tuber flesh; plants may show yellowing leaves
Treatment: Remove and destroy affected tubers; do not compost; disinfect tools
Prevention: Use certified disease-free slips; cure tubers properly after harvest; rotate crops; avoid damaging tubers during harvest
Disease Fusarium Wilt Fusarium oxysporum f. sp. batatas
Symptoms: Yellowing and wilting of lower leaves progressing upwards; brown discolouration of stem vascular tissue; stunted growth
Treatment: Remove and destroy affected plants; do not compost
Prevention: Use disease-free slips; rotate crops on a 3-4 year cycle; improve soil drainage; avoid overwatering
Growing Conditions
| Min. soil temperature | 18°C |
| Germination temperature | 21–30°C |
| Base growth temperature | 12°C |
| Min. daylength to start | 10.5h |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Sweet Potato?
- Plant Sweet Potato 30cm apart with 75cm between rows.
- When can I harvest Sweet Potato?
- Sweet Potato is ready to harvest approximately 120 days after transplanting.
- What grows well with Sweet Potato?
- Sweet Potato grows well with broad beans, runner beans, sweetcorn.
- Is Sweet Potato frost hardy?
- Sweet Potato is classified as Tender.
