When to plant corn – for a bumper harvest of this family favorite

Once you know when to plant corn, you’ll be able to grow and enjoy a fresh crop from your own vegetable garden. Corn has been harvested in North America for over 4000 years, making it a true American icon in the vegetable world.

Full of Vitamin C, corn is a delicious and healthy addition to any dinner plate, and is a firm family favorite – even veg averse children will happily tuck into a plate of the sweet, juicy kernels. It’s really easy to learn how to grow corn, too, making it a must-have addition to the vegetable patch.

When to plant corn – from seed indoors

If you are planning to start your corn seeds indoors as part of your vegetable garden ideas, the best time to plant them is about 2 weeks before your last frost date – which will differ depending on where you live, and could be as early as the start of April to as late as the end of May.

Corn is a tender, warm season annual and needs a soil temperature of about 60°F (15°C) in order to grow well. Starting the plants indoors on a sunny windowsill, or as one of the crops on your list when planning a greenhouse, is a great way to get a head start.

Don’t forget that if you plant corn seedlings indoors, they 'will need to be hardened off to outdoor conditions before transplanting, after the threat of frost has passed,' advises Philadelphia based Allison Sidhu of the Gardener’s Path.

When to plant corn – from seed outdoors

When thinking about when to plant corn, your specific climate has to be taken into account. 

'In the South of the US, seeds may be sown outdoors in May. In other parts of the country, sow  seeds in the cold frame or under a cloche in early May,' advises Frederick Leeth, writer for the Backyard Gardener. 

It’s important to check your exact USDA hardiness zone and to take the weather into consideration before sowing. Be sure to make sure your average temperatures in early spring aren’t continuously below 60°F (15°C) as your corn seeds may struggle to germinate in colder conditions.

'The risk of all frost has usually already passed by May so it is generally safe to plant corn outside,' explains Mr Mitford, kitchen gardener at Hawkstone Hall

'To help improve the germination rate of your seeds and to speed germination along, soak them overnight in tepid water before planting,' advises Allison Sidhu. 

Corn is sown in blocks because the plants are pollinated by the wind. They should be sown in a 'sunny position, and provide a windbreak for areas exposed to strong winds,' advises Frederick.

What is the best month to plant corn?

The best month to plant corn will depend on your USDA plant hardiness zone and your local climate.

As a general rule, 'sweet corn seeds can be planted outdoors two to three weeks after the last average frost date in your area, or started indoors about two weeks before your last average frost date in the spring,' Advises Allison. 

Plan plant your corn seeds along with other warm season crops, such as zucchini or  pumpkins, as part of your vegetable calendar.

If you are starting your seedlings before the last frost, be sure to keep them protected in a greenhouse or with a cloche. 

What is the latest date to plant corn?

The latest date to plant corn will largely depend on the variety you are growing. There are early, midseason and late cultivars that can be planted at different times. When to harvest corn? Some varieties of corn are ready to harvest within two months of planting, whereas others take closer to three. When planning when to plant corn the growing period needs to be factored in to the timings. 

The latest possible time for planting corn will depend on your specific growing zone, but look to get plants in the ground by at least mid-summer to give the plant enough time in the sunshine to grow strong. 

Be sure that the risk of frost has passed before being tempted to sow directly outdoors, and companion planting alongside beneficial crops will help achieve a healthy harvest.

'You do not want to plant different corn together, as the crop will turn out bad,' warns Holli Schippers from Sunnyside Nursery . Try to keep the same varieties together when planting out corn.