Everything you need to know about growing sweetcorn seeds
Growing Sweetcorn Seeds: Questions & Answers
(Updated 02/03/2025)
When is the best time to plant sweet corn seeds?
Sweet corn seeds should be planted in late spring when soil temperatures reach at least 15°C, ideally between 18-24°C for good germination. Cold soil can delay sprouting and lead to poor growth. In warmer climates, a second crop can be planted in midsummer for a late-season harvest. Avoid planting too early, as frost can damage young seedlings.
How do I plant sweet corn seeds?
Sow sweet corn seeds directly into well-prepared soil about 2.5-5 cm deep and 20-30 cm apart. Plant in blocks of at least four rows (rather than a single long row) to ensure good wind pollination. Water the soil well after planting, and keep it consistently moist during germination, which usually takes 7-10 days. Thin weaker seedlings if necessary to maintain strong growth.
What type of soil is best for growing sweet corn?
Sweet corn thrives in well-draining, nutrient-rich soil with a pH between 6.0 and 6.8. Loamy or sandy soil enriched with compost or aged manure provides the best conditions for growth. Corn is a heavy feeder, so adding organic matter or a balanced fertiliser before planting improves yields. Avoid compacted or waterlogged soil, as poor drainage can stunt root development.
How much sunlight does sweet corn need?
Sweet corn requires full sun, meaning at least 6-8 hours of direct sunlight per day. Insufficient sunlight can lead to weak plants and reduced ear production. In cooler climates, planting in the sunniest spot ensures proper development. If growing in very hot regions, provide occasional watering during extreme heat to prevent stress.
How often should I water sweet corn?
Corn needs consistent moisture, especially during germination and ear development. Water deeply at least once a week, providing about 2.5 cm of water per week, adjusting based on weather conditions. Dry conditions during pollination can reduce kernel formation, leading to poorly filled ears. Mulching around the base helps retain soil moisture and reduce weeds.
How long does it take for sweet corn to be ready to harvest?
Sweet corn varieties typically take 60-100 days to mature, depending on the type and growing conditions. Ears are ready to harvest when the silks turn brown, and kernels release a milky liquid when pressed. If the liquid is clear, the corn is not yet ripe; if it's doughy, it may be overripe. Harvest in the morning for the best sweetness and flavour.
Does sweet corn need fertiliser?
Yes, corn is a heavy feeder and benefits from fertilisation. Apply a balanced fertiliser (such as 10-10-10) when planting, then side-dress with nitrogen-rich fertiliser (such as blood meal or composted manure) when plants are 30 cm tall and again when tassels form. Too little nitrogen can result in yellowing leaves and small ears. Avoid excessive fertilisation, which can lead to excessive stalk growth with fewer ears.
Can I grow sweet corn in containers?
Sweet corn is challenging to grow in containers because it has deep roots and requires ample space for pollination. If growing in a container, choose a large pot (at least 30-40 cm deep and wide) and plant at least 4-6 plants for proper pollination. Use rich, well-draining soil and water frequently, as containers dry out quickly. A dwarf variety is best suited for container growth.
How do I ensure good pollination for sweet corn?
Corn is wind-pollinated, so planting in blocks (at least 4 rows) instead of single long rows increases the chances of successful pollination. Shaking the stalks gently when tassels appear can help distribute pollen more evenly. Poor pollination leads to ears with missing kernels. Avoid planting near taller crops that might block wind movement.
How do I prevent pests and diseases in sweet corn?
Common corn pests include corn earworms, aphids, and cutworms, which can be controlled with row covers or insecticidal soap. Crop rotation helps prevent soil-borne diseases like corn smut and rust. Keeping the garden free of debris and weeds reduces pest hiding spots. Encouraging natural predators like ladybugs and birds also helps control pests naturally.
Where should I plant sweet corn?
Sweet corn needs full sun, at least 6-8 hours per day, to thrive. Choose a location with well-drained, fertile soil. Corn is wind-pollinated, so plant multiple rows close together (rather than one long row) to ensure good pollination and full kernels. Avoid planting corn in a windy area if possible, as this can interfere with pollination.
How deep and far apart should I plant sweet corn seeds?
Plant sweet corn seeds about 2.5-5 cm deep and 15-20 cm apart in rows. Space the rows about 75-90 cm apart. Thin seedlings to about 30 cm apart once they have a few leaves. This gives each plant enough room to grow and develop full-sized ears.
How often should I water sweet corn?
Sweet corn needs consistent moisture, especially during germination and ear development. Water deeply at the base of the plants when the top 2.5 cm of soil feels dry. Avoid overhead watering, as this can wash away pollen and lead to disease problems. Mulching around the base of the plants helps retain moisture.
How do I know when sweet corn is ready to harvest?
Sweet corn is ready to harvest when the silks turn brown and the kernels are plump. Gently peel back the husk and pierce a kernel with your fingernail. If the juice is milky, the corn is ready. If it's watery, it's too immature, and if it's doughy, it's overripe. Harvest corn in the morning when it's cool for the best flavor.
What are some common problems with sweet corn?
Sweet corn can be susceptible to pests like corn earworms, corn borers, and Japanese beetles. Diseases like common smut and Stewart's wilt can also be a problem. Practice crop rotation and choose resistant varieties when available.
How do I prevent pests and diseases in sweet corn?
Inspect plants regularly for signs of pests and diseases. Handpick pests or use appropriate insecticides if necessary. Provide good air circulation and avoid overhead watering to minimize disease risks. Remove and destroy any diseased plants to prevent the spread of infection.
How do I store sweet corn?
Sweet corn is best eaten fresh, but it can be stored in the refrigerator for a few days. For longer storage, you can freeze the kernels. Cut the kernels off the cob and blanch them in boiling water for a few minutes before freezing.
Can I save sweet corn seeds?
Saving sweet corn seeds can be tricky because most commercially available sweet corn varieties are hybrids. Hybrid corn will not produce true-to-type plants from saved seeds. If you want to save seeds, choose an open-pollinated variety and isolate it from other corn varieties to prevent cross-pollination.