CultivaOS
Herbarium
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Sweetcorn

Zea mays

Fruiting

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

Issues & threats

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Wilting

Environmental

Plants 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.

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Poor germination

Environmental

Seeds 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.

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Damping off

Fungal disease

Pythium 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.

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Yellowing leaves

Environmental

Leaves 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.

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Stunted growth

Environmental

Plants 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.

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Chewing damage

Pest

General 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.

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Sap-sucking pests

Pest

General 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.