Sweet corn is the taste of high summer, and it is at its best eaten within minutes of picking — the sugars start turning to starch the moment the ear is cut. It is a big, bold plant that needs space and sun, but a small block of corn in a sunny garden is one of the most rewarding things you can grow.
Corn is wind-pollinated, which is the one thing to understand before you plant it: a single long row pollinates badly, while a block of plants pollinates well.
Sweet Corn at a glance
| Growing factor | What sweet corn need |
|---|---|
| Sun | full sun |
| Soil pH | 6.0–6.8 |
| Days to germination | 7–10 |
| Days to maturity | 60–90 |
| Spacing | 12–15 inches |
| Water needs | moderate |
| Cold tolerance | tender |
| Family | Poaceae |
Starting seeds
This is a direct-sow crop: the seed goes straight into the garden where it is to grow, and the plants are not transplanted. Prepare a fine, weed-free seed bed, sow at the depth shown on the seed packet, and keep the bed evenly moist until seedlings appear — expect germination in 7–10 days.
Sow too early into cold, wet soil and germination stalls; sow too late and the plants run out of season. Use our frost-date calculator and the hardiness-zone finder to place your sowing window. Zones 11–13 are frost-free, so sowing windows there are set by heat and rain rather than frost — check your local extension service.
Sweet corn is sown direct where it is to grow, once the soil is warm — seed sown into cold soil often rots. Sow in a block rather than a single long row, so the wind can carry pollen from plant to plant, and water the drill before sowing. Germination is usually quick in warm soil, and a second sowing a few weeks later extends the season.
Transplanting and planting out
Corn is not usually transplanted, though you can start a few plants in pots if you want the earliest possible ears — handle them gently, as the roots dislike disturbance. The main job is spacing: thin seedlings to their proper spacing so each plant has room to grow strong, and earth up a little soil around the base of the stems once the plants are knee-high to help anchor them against wind.
Space plants 12–15 inches apart — crowding is one of the commonest causes of small harvests. Our plant-spacing calculator works out how many plants fit your bed.
Soil and feeding
Sweet Corn grow best in rich, well-drained soil with plenty of organic matter. Dig in compost before planting: it improves heavy soil, helps light soil hold moisture, and feeds the soil life that feeds your plants. Aim for a soil pH of 6.0–6.8 — a simple soil test will tell you where you stand, and garden lime or sulfur can nudge pH up or down over a season, so test before you amend rather than guessing.
Feed lightly and steadily rather than in one heavy dose: too much fast nitrogen late in the season pushes leafy growth at the expense of the part you eat. Our fertiliser calculator works out amounts for your bed size, and the soil-volume calculator tells you how much mix a new bed needs.
Watering
Water needs are moderate: keep the soil evenly moist, watering deeply when the top inch or two dries out. Deep, infrequent watering builds deeper roots than a daily sprinkle.
Water at the base of the plant, in the morning, so the leaves dry quickly and the water reaches the roots. Our watering calculator gives a starting point for your bed size, and the watering schedule generator can build a routine around it. A mulch layer cuts evaporation and keeps moisture even.
Sunlight and temperature
Sweet Corn need full sun — a spot that gets sun for most of the day. Our sunlight calculator can check your spot.
This crop is rated tender for cold tolerance, so frost will kill it: it needs warm soil and frost-free nights, and should only go outside once all danger of frost has passed. In Zones 11–13, which are frost-free, it can be grown for much of the year, though the hottest months may still stress it. Our hardiness-zone finder will confirm your zone, and the frost-date calculator gives you the frost dates to plan around.
Pests and diseases
The pests and diseases most often reported on sweet corn are aphids, slugs, cutworms. Healthy, well-watered plants resist attack better than stressed ones, and rotating beds so the Poaceae family does not repeat in the same spot helps keep soil-borne problems down.
- Aphids — small sap-sucking insects on new growth; wash off with a strong jet of water and encourage ladybirds.
- Slugs — chew ragged holes in leaves at night; water in the morning so the surface dries by evening.
- Cutworms — caterpillars that chew through young stems at soil level; a cardboard collar around each stem protects it.
Inspect plants weekly, especially leaf undersides, and act early. Our pest-identifier helper can help identify what you are seeing.
Companion plants
Good companion plants for sweet corn include:
- Marigolds — their roots discourage some soil pests
- Basil — attracts pollinators
- Onions — their scent is said to confuse pests
- Lettuce — shallow-rooted, fills gaps without competing
Our companion-planting finder can suggest more pairings for your bed plan.
Harvesting
Sweet corn is ready when the silks turn brown and dry, and a kernel pricked with a thumbnail spurts milky juice. Pick ears in the morning and cook them the same day — ideally within the hour — because the sweetness fades fast once picked. Twist the ear down and pull it away from the stem, and check the whole block regularly, since ears ripen over a week or two rather than all at once.
Expect the crop to be ready about 60–90 days after sowing, though weather and variety shift that window by a week or two either way. Our harvest-date calculator works out your expected harvest date from your sowing date, and the vegetable-yield estimator can estimate how much a bed should produce.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Ears with missing kernels | poor pollination | Corn is wind-pollinated, so plant in a block rather than a single row, and avoid planting different types too close together. |
| Small ears | crowding or dry soil while ears are filling | Thin to the proper spacing, feed and water well while the ears are forming, and mulch to hold the moisture in the soil.. |
| Plants blown over in wind | shallow roots and tall stems | Earth up soil around the base of the stems as plants grow, and plant in a sheltered spot if your garden is windy. |
Ears with missing kernels
Corn is wind-pollinated, so plant in a block rather than a single row, and avoid planting different types too close together.
Small ears
Thin to the proper spacing, feed and water well while the ears are forming, and mulch to hold the moisture in the soil..
Plants blown over in wind
Earth up soil around the base of the stems as plants grow, and plant in a sheltered spot if your garden is windy.
Frequently asked questions
When should I plant sweet corn?
Start seeds indoors before your last frost and plant out only after all frost danger has passed, since this is a tender crop. For zone-specific timing, see zone 5 or zone 7, and check your local extension service for the dates that fit your area.
How long do sweet corn take to grow?
Sweet Corn take 60–90 days from sowing to maturity, and seed germinates in 7–10 days. Weather and variety shift the harvest window by a week or two, so judge readiness by look and feel rather than the calendar alone.
How far apart should I plant sweet corn?
Space plants 12–15 inches apart — that is the room a mature plant needs, and crowding means poor airflow and small harvests. Our plant-spacing calculator works out how many fit your bed.
Can I grow sweet corn in a small garden?
Yes, if you can spare a sunny block of ground — a square of plants pollinates far better than a single row, so even a small block of a dozen or so plants can give a useful crop. Choose a compact variety if space is tight, and remember that corn is a tall plant, so put it where it will not shade your other vegetables.