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How to sow cucumber

Quick overview
- Best time: sow under cover 3–4 weeks before last expected frost, or sow direct outdoors after soil reaches consistently 15°C–18°C.
- Soil: fertile, well‑drained, rich in organic matter; pH 6.0–7.0.
- Temperature: germination optimal 18–25°C.
- Sowing depth: 1–2 cm.
- Seed spacing: indoors in pots or modules: one seed per cell; outdoors or in growbags: thin to 30–45 cm between plants (depending on variety).
- Light: plenty of bright light once seedlings emerge; avoid cold drafts.

Step‑by‑step (indoor sowing, recommended for cooler climates)
1. Prepare compost and pots
- Use free‑draining multi‑purpose compost with added compost or well rotted manure for extra fertility. Fill 7–9 cm pots or modules, firm lightly.

2. Sow seeds
- Place one seed 1–2 cm deep in each pot or cell. Water gently to settle compost.

3. Provide warmth
- Keep pots at 18–25°C. Use heated propagator or warm windowsill. Germination usually 5–10 days.

4. Light and ventilation
- Move seedlings to bright light as soon as they appear. Reduce temperature a little by day to encourage sturdier growth. Provide gentle airflow to reduce damping‑off.

5. Pot on and feed
- When seedlings show 2–3 true leaves, transfer to larger pot if needed. Start weekly feed with balanced liquid feed or dilute tomato/cucumber fertiliser.

6. Harden off
- Gradually acclimatise plants to outdoor conditions over 7–10 days before planting out or into greenhouse.

Planting out and training
- Plant into greenhouse, polytunnel or sheltered sunny site after risk of frost has passed and when soil/air are warm. Space plants 30–45 cm apart along rows or use single plants in growbags.
- Provide support: trellis, canes or string to train vines upwards. Training saves space and improves air circulation.

Outdoor direct sowing
- Sow seeds 1–2 cm deep in warm soil from late spring onwards. Sow in hills of 3 seeds, thin to strongest seedling per hill. Direct sowing suits early summer in reliably warm sites.

Watering and care
- Keep soil consistently moist but not waterlogged. Water at soil level to avoid wetting foliage.
- Mulch to conserve moisture and suppress weeds.
- Side‑dress with compost or feed fortnightly during heavy fruiting.

Common problems
- Poor pollination in greenhouse: hand‑pollinate flowers if necessary.
- Powdery mildew and downy mildew: ensure good airflow, avoid overhead watering.
- Pests: aphids and slugs can be an issue; monitor and control early.

Harvest
- Pick cucumbers when fruit reach variety‑specific size and before seeds harden. Regular harvesting encourages more fruiting.

Variety note
- Choose variety suited to greenhouse (parthenocarpic varieties do not need pollination) or outdoor cropping.

Happy sowing — cucumbers are quick to reward once warm conditions are established.
On page one

Choosing

How to sow cucumber Quick overview - Best time: sow under cover 3–4 weeks before last expected frost, or sow direct outdoors after soil reaches consistently 15°C–18°C. - Soil: fertile, well‑drained, rich in organic matter; pH 6.0–7.0. - Temperature: germination optimal 18–25°C. - Sowing depth: 1–2 cm. - Seed spacing: indoors in pots or modules: one seed per cell; outdoors or in growbags: thin to 30–45 cm between plants (depending on variety). - Light: plenty of bright light once seedlings emerge; avoid cold drafts. Step‑by‑step (indoor sowing, recommended for cooler climates) 1. Prepare compost and pots - Use free‑draining multi‑purpose compost with added compost or well rotted manure for extra fertility. Fill 7–9 cm pots or modules, firm lightly. 2. Sow seeds - Place one seed 1–2 cm deep in each pot or cell. Water gently to settle compost. 3. Provide warmth - Keep pots at 18–25°C. Use heated propagator or warm windowsill. Germination usually 5–10 days. 4. Light and ventilation - Move seedlings to bright light as soon as they appear. Reduce temperature a little by day to encourage sturdier growth. Provide gentle airflow to reduce damping‑off. 5. Pot on and feed - When seedlings show 2–3 true leaves, transfer to larger pot if needed. Start weekly feed with balanced liquid feed or dilute tomato/cucumber fertiliser. 6. Harden off - Gradually acclimatise plants to outdoor conditions over 7–10 days before planting out or into greenhouse. Planting out and training - Plant into greenhouse, polytunnel or sheltered sunny site after risk of frost has passed and when soil/air are warm. Space plants 30–45 cm apart along rows or use single plants in growbags. - Provide support: trellis, canes or string to train vines upwards. Training saves space and improves air circulation. Outdoor direct sowing - Sow seeds 1–2 cm deep in warm soil from late spring onwards. Sow in hills of 3 seeds, thin to strongest seedling per hill. Direct sowing suits early summer in reliably warm sites. Watering and care - Keep soil consistently moist but not waterlogged. Water at soil level to avoid wetting foliage. - Mulch to conserve moisture and suppress weeds. - Side‑dress with compost or feed fortnightly during heavy fruiting. Common problems - Poor pollination in greenhouse: hand‑pollinate flowers if necessary. - Powdery mildew and downy mildew: ensure good airflow, avoid overhead watering. - Pests: aphids and slugs can be an issue; monitor and control early. Harvest - Pick cucumbers when fruit reach variety‑specific size and before seeds harden. Regular harvesting encourages more fruiting. Variety note - Choose variety suited to greenhouse (parthenocarpic varieties do not need pollination) or outdoor cropping. Happy sowing — cucumbers are quick to reward once warm conditions are established.

by Gwenaëlle
5 April 2026
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