Germination temperature
Minimum soil temperature about 16°C (60°F); fastest at 25-35°C (77-95°F).
Vegetable growing guide
Cucumber is a fast warm-season vine, native to the Himalayan foothills, that germinates in 3-6 days in warm soil and starts cropping about two months after sowing. Give it warmth, steady water and a trellis, and keep the leaves dry to hold off mildew.
Minimum soil temperature about 16°C (60°F); fastest at 25-35°C (77-95°F).
About 1.3 cm (1/2 inch).
About 3-4 days at 25-30°C; about 13 days at 15°C (59°F).
No light needed for germination; full sun for plants.
None needed.
Direct sowing is usual; transplants must go out young, at 3-4 weeks, without root disturbance.
Sow dry seed into warm soil. Soil temperature, not seed treatment, decides how fast cucumbers come up.
Not needed. The seed coat lets water in readily.
Not needed. Cucumber is a tropical-origin crop with no cold requirement; cold soil only delays or prevents germination.
Not needed, but optional. A soak of a few hours can save a day in marginal conditions; sow soaked seed immediately into warm, moist soil, because soaking does not help seed sown into cold ground.
Harrington's data give a minimum of about 16°C (60°F), an optimum range of 16-35°C (60-95°F) and a maximum of about 41°C (105°F); at 10°C (50°F) there is little or no germination. The University of Minnesota advises waiting for at least 21°C (70°F) at 2.5 cm (1 inch) depth before sowing outdoors.
Sow about 1.3 cm (1/2 inch) deep. Outdoors sow seeds about 5 cm (2 inches) apart in a row, or 3-4 seeds per hill.
Warm, fertile, well-drained soil with pH 6.0-6.5. For transplants use individual pots or biodegradable cells, one or two seeds each.
Keep soil moist but not soggy until emergence; cold, wet soil is the main cause of poor stands.
Seed germinates under its soil cover. Seedlings need strong light straight away or they stretch.
Harrington's figures: about 13 days at 15°C (59°F), 6 days at 20°C (68°F), 4 days at 25°C (77°F), and 3 days at 30-35°C (86-95°F).
Start seed indoors no more than about 4 weeks before planting out; 3-week-old transplants are standard in protected cropping. Plant after the last frost, once nights stay warm. Water beforehand and set the whole root ball in without breaking it: cucumbers have a taproot and check badly when roots are disturbed.
Thin direct-sown seedlings to 20-30 cm (8-12 inches). Put a 90-120 cm (3-4 ft) trellis or netting in at planting so tendrils find it early. Water about 25 mm (1 inch) per week at the base, and do not add straw mulch until the soil is above about 24°C (75°F).
Cause: downy mildew (Pseudoperonospora cubensis), spread by wind and splashing water and favoured by wet, humid weather; infection is most severe at about 15-20°C (59-68°F). It is a serious risk in monsoon and humid conditions. Fix: grow resistant varieties such as Marketmore 76, trellis plants, space them widely, water by drip at the base, and remove badly affected plants.
Cause: powdery mildew, which spreads fastest on crowded plants with poor airflow. Fix: choose mildew-resistant varieties, improve airflow, and keep watering at soil level.
Cause: the first flowers are male and drop naturally, or bees are scarce in cold, rainy or cloudy weather; all-female (gynoecious) varieties also need a pollinizer unless they are parthenocarpic. Fix: wait for female flowers (with a tiny cucumber behind them), avoid insecticides when bees are active, and remove row covers at flowering.
Cause: sowing into soil below about 16°C (60°F). Fix: wait for warm soil, use black plastic mulch to warm the bed, or start in pots indoors.
Cause: bitterness varies by variety and is concentrated near the skin and blossom end; yellow, seedy fruit were left on the vine too long. Fix: choose non-bitter varieties and pick slicers before the skin yellows.
Marketmore 76 is an open-pollinated Cornell slicer (about 67-70 days) that needs bees and carries resistance to downy mildew, powdery mildew, scab and cucumber mosaic virus. Beit Alpha is a Middle-Eastern slicing type with short, smooth, thin-skinned fruit about 15 cm (6 inches) long. Greenhouse Beit Alpha cultivars are all-female and parthenocarpic, setting fruit without pollination; grow open-pollinated seed where bees can reach it.
Vertical growing gives straighter fruit, better airflow and fewer leaf diseases. Trellised plants dry out faster, so check water more often.
Harvest every few days. Beit Alpha types are best picked young, at 3.8 cm (1.5 inches) across or less. Regular picking keeps vines producing.
Cucumbers want warm days and nights; plan sowings so fruiting avoids the most humid weeks, when downy mildew spreads fastest.
Grow Beit Alpha, Summer Green and Marketmore cucumbers from our seed range.
It is not necessary. Warm soil matters far more: seed takes about 13 days to emerge at 15°C but only 3-4 days at 25-30°C. A short soak is optional if you sow straight into warm, moist soil.
Yes, if they are young (3-4 weeks) and grown in individual pots so the root ball is not broken. Older or bare-root seedlings often stall.
Modern greenhouse Beit Alpha hybrids are parthenocarpic and set fruit without pollination. If your seed is open-pollinated, grow it outdoors or let pollinators in to be safe.
Downy mildew makes yellow, angular spots bounded by leaf veins with grey-purple growth underneath. Powdery mildew is a white, dusty coating on the upper leaf surface and stems.