Sweetcorn

Hard to find truly fresh in the shops: growing your own is the only way to eat sweetcorn at its best. Sow in blocks, water well, and harvest within hours of picking for the full flavour.

Written by Yemi · Last reviewed August 2026

Maturing this month

First sprouts in 5–10 days

Difficulty

Sweetcorn should be ready to harvest this month. Check for size and colour.

Growing Calendar

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Sow

Transplant

Harvest

This month: Sep

Log to journal

Ready to harvest now

•Check size and ripeness
•Harvest regularly
•Store or use fresh

Sowing Guide

What you'd find on the seed packet

Sow Depth

2.5cm

Spacing

45cm between plants in each direction (block planting)

Germination

5–10days

Thinning

One plant per station: sow two seeds and remove the weaker seedling

Grower's Note

A block of 4×4 plants (16 total) is the minimum for reliable pollination. Supersweet varieties have better flavour but are less vigorous: use normal or extra tender sweet types in colder regions.

Recommended Varieties

'Swift' holds an RHS Award of Garden Merit, an extra-tendersweet variety that grows and matures quickly, useful in a shorter UK season. 'Mirai Picnic' also holds an AGM and stays more compact with smaller cobs, but typically gives you at least two per plant. For organic growing, The Organic Gardening Catalogue lists 'Golden Bantam' as an open-pollinated heirloom alternative, useful since modern sugary-enhanced hybrids like 'Swift' aren't typically sold as organic or untreated seed.

Planting Out Guide

Best spaces, conditions and how to plant out

Plant Spacing

35–45cm each way

Best Grown In

Open ground, large raised beds

Conditions

Full sun, sheltered. Well-drained, fertile soil. Must be planted in a block for wind pollination.

Grower's Note

Never plant in a single row: block planting ensures the cobs are wind-pollinated. Harvest when silks have turned dark brown.

Growing Stages

Approximate weeks from sowing to harvest

Sprouting

1wks

Seeds germinate and first leaves emerge. Keep warm and moist.

Establishing

6wks

Root system develops and plant builds structure. Pot on if needed.

Maturing

14wks

Plant reaches full size and begins producing. Harvest at peak.

Total~21 weeksfrom seed to harvest

Companion Plants

Plant these nearby for natural pest control, better yields, and healthier soil.

Pumpkin

Suppresses Weeds

Interplanting with pumpkin fills the gaps between Sweetcorn plants, leaving less bare soil for weeds.

Beans

Fixes Nitrogen

Beans fix nitrogen from the air into the soil as they grow, feeding a hungry neighbour like Sweetcorn.

Nasturtium

Repels Pests

Nasturtium acts as a sacrificial trap crop, drawing aphids and cabbage white caterpillars away from your Sweetcorn.

Squash

Suppresses Weeds

Interplanting with squash fills the gaps between Sweetcorn plants, leaving less bare soil for weeds.

Climate Control

Today

—C

Humidity

—%

Water

Daily

Sunlight

6+ hours direct sun

Watch Out For

Cold soil below 10°C causes poor germination and sluggish growth: do not plant out until the soil has warmed; even a June planting will still crop in time

Mice steal freshly sown seeds: protect outdoor sowings with fleece or a cloche until seedlings are well established

Sweetcorn needs consistent watering once cobs begin to swell: irregular moisture at this stage causes gapped cobs with missing kernels

Pests & Problems

Full guide

Aphids

Colonies on tassels and leaf undersides

Jun–Aug

Frit Fly

Dead heart in young plants: the central shoot turns yellow and dies

Apr–Jun

Smut

Grey-white galls on cobs and stems that burst to release black spores

Jul–Sep

What You'll Need

Equipment for growing sweetcorn

Organic Seeds: Just Seed

Certified organic, open-pollinated

Organic Liquid Seaweed

Shropshire Seaweed: soil & plant feed

Coco Dots Pellets: Coco & Coir

50-pack seed starters, biodegradable

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Grown Organically

Every method in this guide works with natural systems: no synthetic chemicals, no shortcuts.

Read our approach

Common Questions

About growing Sweetcorn in the UK

Why must I plant sweetcorn in a block?

Sweetcorn is wind-pollinated: pollen falls from the male tassels at the top onto the female silks below. In a single row, most pollen blows away and few cobs are pollinated. A block of at least 4×4 plants ensures the pollen clouds stay within the planting area.

When is sweetcorn ready to harvest?

Harvest sweetcorn when the silks at the top of the cob have turned dark brown, and the cobs feel plump and full. Test by peeling back a small section of husk and pressing a kernel: the juice should be milky, not clear or starchy. Eat as soon as possible after harvesting.

Can I grow sweetcorn in the UK?

Yes, modern varieties bred for UK conditions reliably produce cobs in a good summer. Choose early varieties (Swift, Earlibird, Lark) and start under glass to give the longest possible season. Sweetcorn needs a sunny, sheltered position to succeed.

Why are my sweetcorn cobs small or empty?

Poor pollination is the most common cause of small or incomplete cobs. This happens when plants are grown in rows rather than blocks, or when weather is very wet and windy during pollination. Shaking the plants gently when tassels are producing pollen can help in poor conditions.

Written from real growing experience, not just research. Read the story behind Pelham Gardens.

Member guides

There's more to growing Sweetcorn than this guide covers.

A Garden Journal to log what worked, a personalised sowing planner in My Garden, and monthly reminders timed to the calendar.

See what's included