Sweetcorn
Zea mays
Sweetcorn is a tall, wind-pollinated grass that should be planted in blocks rather than rows to ensure good pollination and full cob development. It is frost-tender and needs a warm, sheltered site in the UK, growing best in a warm summer. Sugars convert to starch rapidly after picking, so cobs eaten immediately after harvest taste dramatically better than anything shop-bought.
Key facts
- Family
- Poaceae (Grasses)
- Category
- Fruiting
- Sowing window
- Apr–May
- Sowing depth
- 30 mm
- Watering
- medium
- Frost sensitivity
- high
- Days to maturity
- 70-90 days from transplant
- Harvest window
- Aug - Sep
Sowing notes
- -Sow indoors in April; direct sow outdoors in May once frost risk has passed
- -Plant in blocks (not rows) to ensure wind pollination
- -Sugars convert to starch rapidly after picking - cook or eat immediately
Varieties
Earlibird is an early-maturing F1 sweetcorn bred specifically for the shorter UK growing season, producing sweet, tender cobs reliably even in cooler summers. It is one of the most popular choices for UK home growers for its dependability and good flavour. Cobs are medium-sized with a good sugar content.
Golden Bantam is a classic open-pollinated sweetcorn variety dating from 1902, producing 15-20 cm cobs of rich, sweet yellow kernels. It has an old-fashioned, deep sweetness that differs from modern super-sweet F1 varieties. Being open-pollinated, seeds can be saved from year to year.
Issues & threats
Wilting
EnvironmentalPlants are drooping or losing vigour. Most commonly caused by water stress but can also indicate root damage, vascular disease, or heat scorch. Identifying the cause quickly is important as some causes are serious.
Poor germination
EnvironmentalSeeds are emerging unevenly or not at all. Usually caused by soil temperature being too low, seeds sown too deep, poor seed-to-soil contact, or old seed stock.
Damping off
Fungal diseasePythium spp. / Phytophthora spp.
Young seedlings collapse at or just below soil level, caused by fungal pathogens that thrive in overwatered, poorly ventilated growing conditions. Can spread rapidly through a seed tray.
Yellowing leaves
EnvironmentalLeaves are turning yellow, which can indicate a range of problems including nutrient deficiency, overwatering, disease, or natural senescence. Identifying whether the pattern is upper or lower leaves, whole leaves or between veins, is key to diagnosis.
Stunted growth
EnvironmentalPlants are significantly smaller or slower to develop than expected. May be caused by poor soil, nutrient deficiency, root restriction, compaction, pest damage to roots, or disease.
Chewing damage
PestGeneral chewing damage from an unidentified pest, leaving holes or missing leaf sections. May be caused by caterpillars, beetles, or other insects. Inspect at dusk to identify the culprit.
Sap-sucking pests
PestGeneral sap-feeding pest activity causing weakened or distorted growth. May be caused by aphids, whitefly, scale insects, or other sucking insects. Inspect leaf undersides and growing tips to identify the pest.