When to plant sweetcorn?
For the RHS, sow sweetcorn in April, May and June and plant it out in May and June, after the last frost. In Campania the main crop in the regional guide, for grain or forage, is usually sown in mid-April, with an early sowing in late March, in Sicily in April once the soil is at least 12 °C, and Umbria writes no month.
When, by region
| North | Centre | South | |
|---|---|---|---|
| Sowing | The calendar marks April, May and June. Indoors, from mid- to late spring, one seed 2.5 cm (1 in) deep in a deep pot, at 18-21 °C (65-70 °F). Up within two weeks. Plant out in May and June, in late May or early June, after the last frost, once plants are 8-15 cm (3-6 in) tall. Outdoors, in late spring and early summer, only once the soil is above 10 °C (50 °F), 2.5 cm (1 in) deep, in a grid. | Umbria 2025 has grain and silage maize and does not write a sowing month. October-February, on the sheet, is an example of rain for leaching, not a sowing. | In Campania the soil has to sit above 10 °C (50 °F), better close to 12-15 °C (54-59 °F). The main crop is usually sown in mid-April. Early sowings are late March to early April. A month for the late sowings is not written. In Sicily the first crop is April, once the soil stays at least at 12 °C (54 °F), and it is up in about 15 days. Below 10 °C (50 °F) it does not germinate. A sweetcorn chapter, with a month of its own, is not there. |
| Spacing | In a grid, 34-45 cm (13-18 in) each way, two or three seeds at each point, and you keep the strongest plant. Baby corn sits at 20 cm (8 in), in rows and not in a block. Plants reach 2 m (6½ ft), depending on the variety. A pot is possible, with compact varieties and the same spacing, in the largest container you have. From one square metre, count 6-9 cobs. | Umbria does not write a spacing. | In Campania, rows 50-70 cm apart, seed 3-6 cm deep. The table prints 7-8 plants per square metre for early hybrids, 6-6.5 for mid ones, 5-5.5 for late ones and 30-50 for granturchino. The sentence that follows prints 5-8 plants per square metre for granturchino, and then writes that the density reaches 30-50. Without irrigation those stands drop by about 20-30 per cent. Seed 15-25 kg per hectare. In Sicily, 15-30 kg per hectare. A spacing in centimetres, on the sowing sheet, is not written. |
It wants warmth and full sun. Frost stops the plants. Below 10 °C the seed does not start.
April, May and June, May and June for planting out, 2.5 cm (1 in), 18-21 °C (65-70 °F), two weeks, late May or early June, 8-15 cm (3-6 in), 10 °C (50 °F), 34-45 cm (13-18 in), 20 cm (8 in), 2 m (6½ ft) and the 6-9 cobs are from the RHS, on the sweetcorn page. 10 °C (50 °F), 12-15 °C (54-59 °F), mid-April, late March to early April, 3-6 cm, 50-70 cm, 7-8, 6-6.5, 5-5.5 and 30-50 plants per square metre, the 20-30 per cent and 15-25 kg per hectare are from Campania, in the grain or forage chapter. 12 °C (54 °F), about 15 days, 15-30 kg per hectare and the zero below 10 °C (50 °F) are from Sicily, in the grain and silage chapter. Umbria 2025 writes no month. Courgettes, in the same rotation group, are in when to plant courgettes. The months are in the March calendar, April, May, June, August, September and October.
April indoors, June outside
The RHS sows indoors in spring, and the calendar marks April, May and June. One seed 2.5 cm (1 in) deep, in a deep pot, at 18-21 °C (65-70 °F). Up within two weeks. To stretch the harvest, sow an early, a mid and a late variety together, or the same early one in batches a few weeks apart. Plant out in late May or early June, after the last frost, once the plants are hardened off and 8-15 cm (3-6 in) tall. The planting calendar marks May and June.
Outdoors, the RHS suggests it only in milder spots, on light, warm soil, above 10 °C (50 °F), in late spring and early summer. Sow in a grid, not in a long row, at 34-45 cm (13-18 in), two or three seeds to a hole. Baby corn sits at 20 cm (8 in), in rows: the small cobs must not be pollinated. The pot is in starting seeds indoors.
Campania and Sicily, grain and forage
In Campania the chapter covers grain and forage maize, not a separate sweetcorn sheet. The soil at sowing sits above 10 °C (50 °F), better close to 12-15 °C (54-59 °F). The main crop is usually sown in mid-April. Early sowings, late March to early April, use the soil water better and bring harvest forward, with more risk of gaps. Late sowings speed emergence and push flowering towards the dry spell. A month for those late sowings is not written. In April, for grain, mid or late hybrids, FAO classes 500-600, and 600-700 if the crop is forage. As a second crop, for grain, FAO 200-300, and 400-500 if it is green forage or silage. Seed goes 3-6 cm deep, in rows 50-70 cm apart, 15-25 kg per hectare. The mean temperatures it names sit between 21 and 27 °C (70-81 °F), with nights above 15 °C (59 °F) and about 130-150 frost-free days. Above 32 °C (90 °F) the cycle shortens. Above 40 °C (104 °F), in dry air, the pollen dies. Nights at 22-25 °C (72-77 °F) cut the yield. The pH sits between 6.5 and 7.0.
In Sicily the chapter is grain and silage. The first crop is sown in April, once the soil stays at least at 12 °C (54 °F), and it is up in about 15 days. Below 10 °C (50 °F) it does not germinate. At 4-5 °C (39-41 °F) the plants die or stay stressed. The optimum sits between 20 and 27 °C (68-81 °F). The pH sits between 6 and 7.5. Seed is 15-30 kg per hectare. Flowering, as a guide, falls in July, and water in July and August covers the central 50-60 days. Grain is cut from the second half of September to the end of October. Silage, while the grain is still filling, is July-August. Sweetcorn appears in a nutrient table, not as a date. Umbria, in 2025, has grain and silage maize and does not write the month. The home plan is in crop rotation.
A block, not a row
Sweetcorn is a grass, and the wind carries the pollen. The RHS plants it in a block, so each plant has neighbours on every side. A long row leaves the cobs half empty. You can also tap the stem once the tassels open. Supersweet varieties do not sit next to the others: a cross takes the sweetness out. Water young plants in dry spells, and again while they flower and the cobs swell. Plants reach 2 m (6½ ft) and, if the wind rocks them, earth them up or stake them. How much is in watering.
In Campania maize is a renewal crop. Outside mountain zones the rotation is five years, with at least three crops and at most one repeat. In the mountains it goes in with at least one other crop, still with at most one repeat. In Sicily the rule is the same five years, and for the repeat the autumn-winter cereals, wheat included, count as crops of the same kind as maize. For the RHS, sweetcorn, with courgettes and pumpkins, goes wherever suits you, without repeating it too often: that is in crop rotation.
In the app
Every plant in the catalogue has its own sowing calendar, and weather alerts for your area help you judge whether to sow now or hold off.
Frequently asked questions
When do I sow in the north?
The calendar marks April, May and June. Indoors, at 18-21 °C, seed 2.5 cm deep. Plant out in May and June, in late May or early June, after the last frost, once plants are 8-15 cm tall. Outdoors only above 10 °C, in late spring and early summer.
What date does Campania write?
Soil above 10 °C, better 12-15 °C. Main crop usually in mid-April. Early sowings in late March to early April. A month for the late sowings is not written. The chapter is grain or forage. In April, FAO 500-600 for grain and 600-700 for forage.
What about Sicily and Umbria?
Sicily, first crop: April, soil steady at least at 12 °C, up in about 15 days. Below 10 °C it does not germinate. Umbria 2025: no month. Sweetcorn, in Sicily, appears in a nutrient table, not as a date.
How far apart?
The RHS: a grid at 34-45 cm, baby corn at 20 cm in rows. Campania: rows 50-70 cm apart, seed 3-6 cm deep, 7-8, 6-6.5 or 5-5.5 plants per square metre depending on how early the hybrid is. The granturchino table prints 30-50, and the next sentence prints 5-8 and then 30-50. Sicily: 15-30 kg of seed per hectare, with no spacing in centimetres.
When are the cobs ready?
The RHS calendar marks August, September and October. A cob is ready when the silks brown and a pierced kernel gives a creamy liquid. In Sicily, grain in the cereal chapter runs from the second half of September to the end of October, and silage in July-August.