Sowing and planting out Sweet Corn

Seeds of sweet corn can be sown outdoors directly into the permanent bed, or started in peat pots under glass and then transplanted in late spring or early summer. Direct sowing is easier, as it eliminates the bother of planting out. On the other hand, it is only suitable in mild, sheltered areas, and even then, a sudden cold spell can end your hopes of a good sweet corn harvest.

Before the development of peat pots, sowing sweet corn indoors was decidedly risky, and a large percentage failed. This is because the roots resent disturbance, and in transferring them from clay or plastic pots to the ground, the roots inevitably suffered. Peat pots, however, can be planted directly into the soil, so the problem of root disturbance is eliminated.

For indoor sowing in mid-spring, use 7.5 cm (3”) diameter peats pots, filled with a good quality seed compost. Put in three seeds per pot, about 1.8 cm (¾”) deep, moisten the compost, and cover the pots with a sheet of black plastic, or glass and brown paper, until germination has taken place. The temperature needed for successful germination is from 10-35°C (50-95°F), and preferably above 16°C (60°F). Provided the temperature is high enough, and the compost is not allowed to dry out, germination should take place within six to twelve days after sowing. As soon as the seedlings are large enough to handle, remove all but the strongest at each pot. Unless it is unseasonably cold, place the pots in a cold frame in the beginning of late spring to harden the young plants off. Lift the light on warm sunny days, replacing it at night or if the weather turns cold.

Transplant them outdoors when the likelihood of frost is past. If the soil is dry, dig a hole for each plant and flood with water before placing the peat pot in the hole. It is a good idea to immerse the peat pot in lukewarm water for a few seconds at this time, to aid in the disintegration of the pot once it is in the soil. Make sure the level of the soil inside the pot is the same as the surrounding soil; if it is too high, the soil in the pot will rapidly dry out, killing the roots, and if it is too low, water may collect in the pot, rather like a sump. Plant the corn either in rows about 35-45 cm (14-18”) apart, with 60-90 cm (2-3’) between rows, or in blocks, having two or more short rows, rather than one long one.

By giving cloche protection, you can sow outdoors in mid-spring; otherwise, wait until late spring or early summer, depending on the weather. It is a good idea to warm the soil up by putting the cloches on about a fortnight before you intend to sow. Sowing under cloches also protects the seeds from attacks by rooks, and the seedlings from frit fly. Remove the cloches in early summer. If you are not giving cloche protection and are bothered with rooks, string black cotton thread oyer and across the rows about 30 cm (1’) above the soil.

To sow, draw out drills 2.5 cm (1”) deep, and 60-90 cm (2-3’) apart, depending on the size of the variety. Sow dwarf varieties in closer rows, 30 cm (1’) apart, to get two rows per cloche. Sow the seeds, which are relatively big and easy to handle, at the rate of five or six seeds per 30 cm (1’) run. Start thinning when the plants reach a height of about 20-25 cm (8-10”), so that they are eventually spaced 35-45 cm (14-18”) apart. As with planting, try to ensure block sowing in squares, rather than long rows.


The reproductive system of sweet corn is more complicated than most other vegetables, but an understanding of it will make it easier to produce good crops. Male and female flowers are borne on the same plant. The male flowers are the rather unattractive, dull brown long tassels at the top of the stalk, while the female flowers, or ‘silks’, are lower down the plant. When the silks are creamy white, wind-borne pollen from the male flowers must come into contact with these for pollination to take place. Once fertilized, the embryonic grains at the base of the silks will begin to grow, with the fully ripened cob as the end product. If the weather is very still and windless at the time pollination would normally occur, gently shake the male tassels to release the pollen. If you cannot see dust-like pollen floating down, then repeat the procedure daily until it is visibly released.

Because corn is wind-pollinated, it is a much safer bet to grow sweet corn in square blocks of planting, rather than in single lines. Although single plants may look attractive when dotted around the vegetable garden, the chances of the pollen successfully reaching the female flowers are greatly diminished.

Lastly, unless you are growing a non hybridized strain, such as Golden Bantam, do not attempt to save the seeds for planting the following year. All of the modern hybrids are the F1 generation, produced by crossing- two selected strains, a process which the nurserymen do every year. Seeds of F1 hybrids do not come true; that is, if planted, the progeny is unlikely to resemble the parent plant. Some F1 hybrid strains, such as Early Extra Sweet, must not be grown anywhere near other varieties of sweet corn, because their flavour will be adversely affected if cross-pollination occurs.

30. August 2013 by admin
Categories: Fruit Gardening, Uncategorized, Vegetable Gardening | Tags: , , , , , , , | Comments Off on Sowing and planting out Sweet Corn


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