Growing Sweetcorn on an Allotment

Sweetcorn is one of the most satisfying allotment crops: fresh-picked cobs are dramatically sweeter than shop-bought. Success depends on warmth, block planting for pollination, steady watering, and timely feeding. Get those right and sweetcorn is reliable and high-yielding.

This guide covers how to grow sweetcorn from seed and plug plants, when to plant, spacing, watering and feeding, pests and diseases, container vs ground growing, and proven ways to improve yields.

🌱 1. Types of Sweetcorn (Why It Matters)

🌽 Supersweet (Sh2)

• Very sweet, longer shelf life

• Needs warm soil to germinate

• Isolate from other maize types

🌽 Sugar Enhanced (SE)

• Sweet and reliable

• Germinates better in cooler soils

🌽 Standard (SU)

• Traditional flavour

• Less sweet, but robust

(All types grow the same way; germination warmth differs.)

🌰 2. Ways to Grow Sweetcorn

From Seed (Most Common)

Pros

• Cheap and reliable

• Wide choice of varieties

Cons

• Needs warmth to germinate

• Vulnerable to mice/birds early on

Plug Plants

Young sweetcorn plants raised in modules.

Pros

• Faster start

• Less seed loss

• Useful in cooler springs

Cons

• More expensive

• Limited variety choice

👉 Both methods work well — warmth and pollination matter most.

🗓️ 3. When to Sow & Plant Sweetcorn

From Seed

• Sow indoors: April–May

• Sow outdoors: Late May–June (soil warm)

Plug Plants

• Plant out: Late May–June

Sweetcorn is frost-tender — wait until all frost risk has passed.

🌾 4. How to Grow Sweetcorn in the Ground

Soil & Position

• Very fertile soil

• Full sun

• Sheltered from strong winds

Add plenty of compost or manure before planting.

Spacing & Layout (Critical for Pollination)

• Plant in blocks, not rows

• Spacing: 30–45cm each way

Block planting improves wind pollination and cob filling.

Planting Tips

• Plant firmly

• Water in well

• Stake in windy sites if needed

🪴 5. Growing Sweetcorn in Containers

Sweetcorn can be grown in containers with care.

Container Guidelines

• Minimum size: 30–40 litres per plant

• Group several pots together for pollination

• Rich, moisture-retentive compost

Container-grown sweetcorn:

• needs frequent watering

• benefits from regular feeding

• produces slightly smaller cobs

Ground growing usually gives the best results.

💧 6. Watering Sweetcorn (Very Important)

Sweetcorn needs consistent moisture, especially when cobs are forming.

Best Practice

• Water deeply and regularly

• Critical stages: tasselling & silking

• Mulch to retain moisture

Dry stress causes:

• poor pollination

• small, poorly filled cobs

🌿 7. Feeding Sweetcorn

Sweetcorn is a heavy feeder.

Feeding Schedule

• Compost before planting

• Start feeding once plants are knee-high

• High-nitrogen feed early, then balanced feed

Well-fed plants produce larger, sweeter cobs.

🐛 8. Common Pests & Diseases

Birds

• Pull up young plants

Control

• Net or fleece early

• Start seeds in modules

Mice

• Eat seeds

Control

• Start indoors

• Sow deeper outdoors

Aphids

• Cluster on leaves

Wash off early or encourage predators.

Poor Pollination

• Patchy kernels

Prevention

• Block planting

• Shake plants gently during flowering

✂️ 9. Harvesting Sweetcorn

When to Harvest

• Silks turn brown

• Kernels release milky sap when pressed

Harvest promptly — sweetness declines quickly after picking.

Most plants produce 1–2 good cobs.

🌾 10. Improving Sweetcorn Yields

• Use block planting

• Water during tasselling

• Feed regularly

• Harvest at peak ripeness

• Choose varieties suited to your climate

Sweetcorn rewards timing and consistency.

⚡ Quick Sweetcorn Growing Tips

• Warm soil speeds germination

• Blocks beat rows every time

• Watering affects kernel fill

• Eat or freeze immediately after harvest

🧠 Key Sweetcorn Principles

• Warmth starts success

• Block planting ensures pollination

• Watering fills kernels

• Freshness matters

Photo by henry perks on Unsplash